Ten years of onchocerciasis control in West Africa: evaluation of the activities of the Onchocerciasis Control Programme in the Volta Basin Area, until June 1984

WORLD HEALTH ORGANIZATION ORGANISATION MONDIALE DE LA SANTE ocP I 84.3 ORIGINAL: FRENCH Page 6 TEN YEARS OF ONCHOCERCIASIS CONTROL IN WEST AFRICA Evaluation of the activities of the Onchocerciasis Control Prograrme in the Volta basin area(unEil June 1984) CONTENTS INTRODUCTION: GENERAL INFORMATION ON ONCHOCERCIASIS CHAPTER I: HISTORY AND STRUCTUBAL FEATURES OF THE ONCHOCERCIASIS CONTROL PROGRAI{ME IN THE VQLTA BASIN REGION: CONTROL STRATEGY. AND'OPERATIONS 1.1 History PREFACE ..,. i. ,. a. r. I 7 L.2 The managerial and implementation strucEures of OCp 1 .2. I Managerial struct.ures L.2.2 Executing and support structurea ... 1.3 Budget and financing I.4 Strategy of OCP and delimitation of its area 13 13 13 13 14 L4 L7 L7 L7 1.4.1 Basic strategy .....r L.4.2 The OCP area L-4.2.1 outline information on phytogeographical zones and dietribution of onchocerciasis and of its vecEors in the parEicipating states .....L.4.2..2 Establish.ing rhe l.imits of the eCp area ........:... 1.5 Vector control operations ........ t... 1.5.1 Selection of insecticides and of methods and equipment for t.heir applicatior ... 1.5 .1.2 Aircraft and equipment for larviciding . . . . L.5.2 ExecuEion of vector control operations Phasing of operaEions Aerial fleet and ground support L7 18 20 20 zo 20 2L 2L 23 | .5 .2.L r.5 .2.2 The issue of this documcnt does not constitute formal publication. lt should not be revrewed, abstracted or quoted without the agreemcnt 9f the World Health Organization. Authors alone are responsible for views expressed in signed articles. Ce document ne constitue pas une publication. ll ne doit faire l'objet d'aucun comptc rendu ou rdsumd ni d'aucune citation sans l'autorisation de l'Organisation mondiale de la Santd. Les opinions exprim6es dans les articles signds n'engagent que leurs auteurs. t I I ocP/84.3 Page 2 Periodicity of larviciding and sites of application OrganizaEion of weekly treatmenE,s Larviciding from the ground The ttextenttt of treatment Evolution of vector control tactics in OCP Insecticide consumption and number of flight hours CHAPTER II: OVERALL RESULTS AND PROBLEMS ENCOUNTERED IN BLACKFLY CONTROL 2.L Ent.omological surveillance Purpose of surveillance The enEomological surveillance netsork Collection of entomological data Utilization of entomological surveillance data. Establishment of entooological indices 2.1. I 2.L.2 2.t.3 2.L.4 29 29 29 29 31 Page L.5.2.3 t.5 .2.4 24 24 25 25 25 27 t.5 .2.5 L.5 .2.6 L.5 .2.7 1.5 .2.8 2.L.4.t 2.L.4 .2 Definition of ABR and ATP Ttre utility of ABR and ATP for assessing Ehe entomological situation 2.1.4.3 Relationships between ATP and ABR 31 32 32 33 33 33 36 36 36 39 2.2 Overall results of vector control Framework for interpretation: Ehe OCP operational zones (002 )2.2.L 2.2.2 2.2.3 The situation prior to operations The entomological situation in 1983 2.3 Problems faced in vector control General Invaded zones and source of reinvasions Modes of migration of blackfly: physiological state and behaviour of migrant females 4L 4L2.3.L.4 Epidemiological and operational impact of reinvasion 2.3.2 Blackfly resistance Eo insecticides 42 Methods of detect.ing resistance Resistances in S. damnosum s.I. CharacEerisEics of res istance Operational inplicacions of resistance 2 .4 Monitoring of the aquatic environrnent .... 45 2.4.1 Historical background; Protocols and methods 45 2.4.2 ImpacE of larviciding on the aquatic fauna 46 2.3.L Reinvasion 2.4.2.1 Short-term ef fects .... 2.3.I.1 2.3.t.2 2. 3. 1.3 2.3.2.L 2.3 .2.2 2.3.2.3 2.3 .2.4 39 39 42 42 43 43 2.4.2.2 Mediurn and lonyterm effecEs 46 46 rt ocPl84.3 Page 3 Page CHAPTER III: REDUCTION OF PARASITE LOAD AND OF PATHOLOGICAL MANIFESTATIONS AFTER EIG}IT YEARS OF VECTOR CONTROL 3.1 Medical evaluation 3.I.1 Parasitological surveillance Methodology .... The parasitological situation in the OCP area after eight years of vector control 3.L.2 Ophthalmological monitoring 3. 1.1. 1 3.1.1.2 48 48 48 48 49 51 51 51 53 53 , 3 .L.2.L 3.r.2.2 Methodology .... Courge of ocular disorders in onchocerciasis patients living in zones that have been under control for more than five years Relations between vector control and ophthahnological findings ....3.L.2.3 3.1.3 Case of the Farako basin 3.1.4 Conclusions regarding the endemic onchocerciasis situation in 1983 in the Progranrme area 3.2 Relations between transmission and clinical manifestations of onchocerciasis ...... 3.2.L Duality of savanna and forest onchocerciases 3.2.2 RelaEions between transuission and clinical manifestations in t,he savanna.. 3.2.3 Relation between transmission and clinical manifestations of onchocerciasis in the West African forest 3.2.4 Relation betrreen transmission and clinical manifestations in intermediat.e zones CHAPTER IV: IMPACT OF OCP ON SOCIOECONOMIC AND HEALTH DEVELOPMENT 4.L The different aspects of socioeconomic and health development 4.2 Onchocerciasis and human ecology 4.2.L Location of villages .... 4.2.2 Size of villages 4.2.3 Land occupancy density 4.2.4 Pattern of habitat 55 56 56 57 57 57 I 60 60 60 60 51 51 61 624.2.5 Professional activities .. 4.2.6 Impact of research inEo human ecology on onchocerciasis control activities and strategy ... 4.3 Reclamation of valleys 4.3.1 Planned economic development projects in zones under control 4.3.2 Settlement and bringing lands under cult,ivation 4.3.3 Protection of the environmenE in areas under control 62 62 62 67 7L NP 184.3 Page 4 4.4 4.5 4.6 Enhancement of working capacity Improvement of the living environment OCP and public health 4.6.1 OCP and Ehe objective of health for all by the year 2000 4.6.2 The public health spinoffs of OCP 4.6.3 InvolvemenE of cormnunities in OCP 4.7 Conclusions regarding inpact of OCP in the socioeconomic sphere CHAPTER V: RESEARCH CONDUCTED AND SUPPORTED BY OCP .. 5.1 The role of research in OCP 5.2 Studies on the vector Simulium darurosum s.1. 5.2.1 Taxonomy and distribution CyEotaxonomy and distribution of species Morphology of blackflies of the S. damnosum complex 5.2.L.3 Biochemical techniques in taxonomy 5.2.2 Bioecology and sampling of preadulE stages Sampling techniques Ecology of preadult stages Preadult cycle Page 7L 72 73 73 73 74 75 t 77 77 78 78 5.2.L.L 5 .2.1.2 5.2.2.3 5 .2.2.4 5 .2.2.5 78 80 80 5.2.2.L 5.2.2.2 80 83 81 81 81 82 82Dynamics of larval populations 5.2.3 Bioecology and sampling of adult blackfly Sampling meEhods Ecology of adult blackflies Dynamics of adult populations 5.2.4 Rearing of S. damnosum s.I. 5.2.5 The vector role of the various sPecies of the S. damnosum complex 5.2.5.1 Experimental transmission 5.2.5.2 Role of different species in natural conditions 5.3 DevelopmenE of new larvicides and new blackfly control meEhods 5.3.1 History and objecrives 5.3.2 Performances exPected from larvicides 5.3.3 The accelerated larvicide development Programne 5.3.4 Results of studies conducEed to date Nutrition of larvae 5.3.5 Formulations of larvicides 5.3.6 Adulticiding .. 5 .2.3.L 5.2.3.2 5.2.3.3 83 83 84 85 85 85 85 87 87 87 88 88 90 90 a a ocP 184 .3 Page 5 5.3.7 Ecological control nethods Page 91 91 91 92 92 92 93 93 93 94 5.3.8 Other control methods J 5.3.9 Development of control methods and future of OCp 5.4 Research on the parasite 5.4.1 Taxonomy of parasites 5.4.2 Biology of parasites 5.4.3 Imunological diagnoeis 5.5 Research on chemotherapy of onchocerciasis 5.5.1 Objectives and organization of research on chemotherapy 5.5.2 Re-evaluation of filaricides 5.5.2.1 Diethylcarbamazine (onc). 5.5.2.2 Suramin 9494 5.5.3 Development of new filaricides 94 1 Procedure for screening of preparations 94 952 Performances of the various compounds tested 5.5.4 The outlook for chemotherapy 95 CHAPIER VI: TRAINING OF PERSoNNEL 96 ANNEX I - List of working papers prepared for the scientific review of the prograrune . 118 ANNEX II - List of figures and t.ables L20 ANMX III - List of symbols and abbreviations 122 5.5.3. 5.5.3. ocP / 84 .3 page 6 PREFACE Onchocerciasis, or "river blindness'r, is one of the major endemic parasitic diseases which are hampering the social and economic development of millions of people in Africa. As stated in the int.roduction to this I0-year progress report,ttonchocerciasis is not only an important disease from the public health viewpoint; it is also a major factor of social and economic disequilibrium, particularly in the African savanna regions" (p. 7). one need only have visited an onchocerciasis-stricken village to realize how much human suffering this parasitic disease causes. Based on the experience accumulated by the entomologisEs of ORSTOM between 1960 and 1965, the report of the Preparatory Assistance Mission Eo the governments of seven West African countries (pAC) was to result in the launching in 1974 of the Onchocerciasis Control Programne in the Volta Basin Area (OCp). WHO was designated as executing agency. Ten years have now elapsed and ne have achieved outsEanding resulEs from the ent.omological, logistic, scientific and technical viewpoints. Since Ehe adoption of the social objective of HFA/2000 through PHC, we are striving t.o establish, in the zones cleared of blackfly, infrastructures for the health systems in correlation with the infrastructures of other sectors such as planning, agriculture, water resources, education, transport and conmunications. One of the specific features of this Programe is the national comittees, operational mechanisrns which rnake it an exemplar of international cooperation for development. It was a welcome idea on the part of Dr E. M. Samba, the Prograrmers dedicated Director, to conduct an evaluaEion of 10 years of onchocerciasis control work in the Volta River basin area. The strategy of the Programne has been based essentially on interruption of the chain of transmission through destruction of the vector by repeaEed insecticide treatment of the fast-flowing reaches of the rivers where larvae of S. damnosum s.1. develop. Reinvasion and resistance of Ehe vector to insecEicides have necessitated readjustments in the aerial operations and in the boundaries of the Prografltrne area. These aerial operations amount to a large-scale logistic exercise and call for quasi-military discipline. Some isolated breeding places remote from the aerial treatment circuits may be treated from the ground or by boat. How could the entomological surveillance which is one of the main activities of the prograruoe have been carried on without Ehe dedicated cooperat.ion of the capturers? In the sphere of health promotion and protection, there are no workers whose devotion to duty can be regarded as of secondary importance. Cohesion among the members of the health team is an earnest of success. To all those who have given of their best to make this Progranune a success I take the present opportunity of paying a very sincere tribute. Another noteworthy feature of this Prograrme is that sufficiently early consideration has been given to Ehe prospecEs for devolution of activities to the participaEing States so that the benefiEs of the Progranrne can be consolidated for Ehe long term. Developmental research work has been given a privileged place in the execution of the Prograrune, which has also played a major role in che training of health development officers. It is my hope that this progress report may inspire its readers to mobilize their efforts more effectively for the promotion of health and peace in the world. Dr Comlan A. A. QUENW WHO Regional DirecEor for Africa I a ocP 184.3 PaEe 7 , INTRODUCTION GENERAL INFORI'{ATION ON ONCHOCERCIASIS Definition and clinical manifestations Human onchocerciasis is a filarial disease due to development in the human dermis of the filaria Onchocerca volvulus. The adults of this species of worm usually live curled into balls in subcutaneous nodules localized adjacent to the bone surfaces (sacrum, iliac crest, Erochanter, ribs, knee, skull, etc.); some deeper nodules are not palpable and some worms move freely abouE in the tissues. The females, which are up to 60 cm long, emit Ehroughout their sexually active life, which lasts from 8 to L2 years, massive quantities of embryos called microfilariae, which lodge preferenEially in the dermis but can invade all the tissues, even the blood, and the urine. Only these rnicrofilariae are pathogenic, their presence in the dermis causing morbid skin changes and, especially during periods of invasion, iEching that is sometimes unendurable and often causes secondary disorders (insonnia, irritability, daytime lethargy, etc.) and are complicated by lesions due to scratching. But it is in the eyeball Ehat. the most serious damage occurs, in particular Eo the cornea, iris and reEina. Some severe eye lesions can reach an irreversible stage and culminate in complet.e blindness under the inpact of repeated and prolonged reinfecEions. These pathological manifestations and their diagnosis have been described by a WHO group of experts (J4O). Developmental cycle of che paras ite Microfilariae are asexual and do not develop directly in man. To continue their cycle, Ehey must of necessiEy pass through an insecE veccor, specifically a blackfly. When the female blackfly (only the fernales are haematophagous) takes a blood meal, it ingests microfilariae which undergo far-reaching rnorphological and anatomical modifications and turn affer seven days on average into infective larvae which nigrate into the vectorts head and mouth parts; Ehese larvae are then inoculated int,o man during a subsequenE blood meal. In man they develop into adult filariae which copulate and the females of which emit microfilariae, Ehus completing the parasitets cycle (Fig. 1). The vector A11 the vectors of human onchocerciasis are blackflies, smal1 diptera looking like humpbacked gnats and a few millimetres long. In West Africa, the disease is Eransnitted by Simulium damnosum s .1. Actuall y, this name embraces a complex of forms of which six, raised to the rank of species, are present in the Programe area and are all inplicated in the transmission of onchocerciasis (rig . 2)'. S. damnosum s.s. and S. sirbanum are savanna f ortrBs,S. soubrense and S. sanctipauli are distributed throughout the forest region and the southern humid savannas of the Prograrrne area, S. yahense 1ives in small forest waEercourses, and S. uamosum is found both in forest and savanna cond itions (see section 5.2.1). Like all blackfly, S. damnosum s.l. lives during the larval and pupae stages in running water, attached to submerged plant or mineral substrates. IEs pre-adult development (egg, seven larval stages and one nymphal stage) takes about a fortnight on average and occurs throughout the year. Though urobile, the larvae feed passively by filtration of nutrient Particles carried by the current. The nymphs, irrnobilized in a cocoon, do not feed. The females of S. darutosum s.l. are exophilic and diurnal. Although small, they are excellent f liers, ".liTEGavelling autonomously over tens of kilometres andaccomplishing migrations over several hundred kilometres. lheir maximum longevity is estimated at one month. I In West Africa the species natural or artificial, up to th conditions are favourable. The repopulaEed aE the start of eacplaces farther to the south. of the S. damnosum complex colonize all types of watercourse, e fifreen-EE-[iEfG1 noith provided rhat th; hydrological , savanna rivers which are dry for part of the year are h rainy season by females migrating from permanent breeding ocP/84.3 Page 8 FIG. 1 LIFE CYCLE OF ONCHOCERCA VOLVULUS Onchocerco volvulus dt I Adult in subculon.ou3 ll3tua Microtllorio. Subculonaou3 ,latua Skin Enl.13 skln ?hrough fly bitr wound Homma \ lnfacllv.3tod. Mlcrofllorio ln rlin Migrot.s lo h.od ond proboscll # I Simuhum Pcnc?rotGs slomoch wollR aloga lorvo /Thoroclc mueclrr2nd rrogr lorvo r,lan,logiorml \-.:-.? wHo Ejr320 I a / \ ocP/84.3 Page 9 FIG. 2 t t 1 ,l I I r J .l4 ,l 'A a wHO Elt201 ocP / 84 .3 Page 10 Tak ing a blood meal initiates in the female of S. damnosum the maturation of its eggs. The physiological and behavioural process which ns, after the blood meal, with the maturation of the oocytes, then continues with the search for a site for oviposition and with laying, and concludes with the search for a new host, constitutes Ehe gonotrophic cycle. It takes from four to six days depending on species, season and climatic zone. The S. damnosun female completes several successive gonotrophic cycles during its adult life: up to five and perhaps more. Each oviposition, particularly the first, leaves traces in the insectrs organism, so it can be deEermined whether it has laid, i.e. whether it is parous. In view of the time taken for the parasite to develop in the vector and the periodicity of the meals, the S. damnosum female is not able to retransmit the parasite until its third blood rneal, ihat is to say on about the twelfth day of its imaginal (adult) life.l The passage in the vector has a considerable thinning-out effect on parasite populations. Ihe percentage of ingested microfilariae that become infective larvae is of the order of l% in savanna conditions and up to 37" in forest areas. Owing to this reduction, the parasite rates in S. damrosum populations by O. volvulus rarely exceed a smal1 percentage figure, even when the prevalence of the parasite in the human populations is close to 1002. Epl4lemiology lluman onchocerciasis is rife in Africa between the fifteeoth north and seveoteenth south parallels. It also exists in the Americas (Mexico, Guatemala, Colonbia, Venezuela, northern Brazi.L and Ecuador) (Fig. 3) and in the south-wesEern part of the Arabian peninsula (Yemen). The African foci account for some 997" of. the estimated 30 million or so onchocerciasis sufferers in the world. In West Africa their numbers range fron 2 lo 2.5 nillion, including 1 mLllion for OCP area alone (see section 1.4.2). In that same region the number of blind persons is estimated at 120 000, including 35 000 or 40 000 in Burkina Faso. The disease is an exclusively rural one (see section 4.2), exEremely debilitating and disabling. Its course is slow, for the clinical manifestations are the cumulative result of numerous infections', hou early severe ocular signs appear depends upon the intensity of transmissionl Ehey may have developed by adolescence. Because of the location of the larval habitats of the vectors, the distribution of the disease corresponds to that of the river systems, which is why the disease is called "river blindness". In view of the rnode of dispersion of blackfly, onchocerciasis foci exhibit a patEern of stratification paralle1 to the watercourses, prevalence, degree of severity and earliness of onset of clinical signs increasing proportionately t.o the proximity of rivers colonized by the vector. In West Africa, the disease is far more serious in the savanna than in forest areas, where cases of blindness are rare. In savanna foci, by contrast, the prevalence of severe eye lesions is tragically high in villages close to watercourses, where blindness may afflict lO7. of Ehe population. Onchocerciasis and the economy Onchocerciasis is not only an imporEant disease from the public health viewpoint; also a major factor of socioeconomic disequilibrium, particularly in the African savanna regions. it is AffecEing first and foremosE small, isolated and remote rural coununities, handicapping and disabling Ehe active and productive strata of the population, the disease contributes todisrupting the already precarious balance of those comrnunitiesr subsistence econornies. This deterioration of their conditions is one of the factors responsible for the abandonuent of riverside lands by the villagers, who retreat to Ehe areas between the ruins. Thus in savanna country it is not unusual for the valleys to be deserted over several kilonetres or I Th. p..-inaginal stages comprise the egg, the larva and the nymph and are aquatic, opposed to the adult or rrimagorr which leads an aerial life.as ocP I 84.3 Page 11 FIG. 3 ONCHOCERCIASIS IN AFRICA AND THE AMERICAS ) , i I t J a J >\ L.-'twr ( o a P v \ (-i.i I(o -t.) 1 ,/%, foci known but prevalence unknown Known foci Distribution of onchocerciasis in Africa (WHO, 1975) o s T- -1 Endemi foci Foci known but prevalence unknown ,,ru, ? t- IL_ I I / Distribution of onchocerciasis in Central and South America (WHO) I I( _) n a.t v) ocP/84.3 Pege 12 even tens of kilometres on either side of Ehe major vratercourses. While onchocerciasis is not always the initial cause of the t'vacuumtt in the valleys, which may be due to otherdiseases such as trypanosomiasis or to historical fact.ors, it neverthlless constitutes an obsEacle to their settlement. In the contemporary African demographic^context, the conquest of these readily irrigable lands, whose area was estimated at 65 000 kmz in the Programme area (245) (see secEion 1.4.2) is an evident necessity, but in the absence of disease clearance measures any movemenE towards settlement, whether spontaneous (due to land shortage) or organized (as parE of a development operation) exposes the populations reintroduced to considerable health risks, and the movement itself is doomed to failure in the medium Eerm. Control of onchocerciasis Control of onchocerciasis is a prerequisite to eliminating tragic health situations and to ensuring the success of development operations: rendering deserted valleys healthful,preventing implantation of Ehe vector in the new settlements, etc. Ihe therapeutic arsenal for combating Ehe parasite is extremely limited. There does exist a macrofilaricide, i.e. a medicament capable of killing the adult worms, namely suramin, and a microfilaricide active against the larval forms, viz. diethylcarbamazine, but the toxicity of these preparations and their side effects on patients preclude their use in mass campaigns. Control of the vector is therefore seen at the present time as the only effective method for combating onchocerciasis. Hence the etrategy of the Prograrme is based on destruction of the vector at its larval stage, the most vulnerable in its cycle. ocP 184.3 Page 13 CHAPTER I HISTORY AND STRUCTURAL FEATURES OF THE ONCHOCERCIASIS CONTROL PROGRAMME IN THE VOLTA BASIN REGION: CONTROL STRATEGY AND OPERATIONS 1.1 History Betrileen 1950 and 1960, extensive research conducted in WesE Africa demonstrated the importance and seriousness of onchocerciasis not only as a public health problen but also as an obstacle to social and economic development. In the zones of intense Eransmission it not only severely affects individuals, but atso jeopardizes the stability of many cortrounities established alongside the rivers (see section 4.1). During the same period, control operations directed againsc Ehe vectors of onchocerciasis were successfully conducted in certain East and Central African foci (08, 64, 133, 152, 165). A few other, small-scale operaEions were carried out in West Africa, for example at Abuya and Kainji in Nigeria (30 , 236). Ber,hreen 1960 and 1965 the ORSTOM entomologisEs serving with OCCGE undertook a piloE campaign against S. damnosum on the Bougouriba river in Upper Vo1ta, followed by larger scale operationsintne@-sinoftheB1ackVo1tainUpperVo1!aandontheFarakoinMa1i. Starting in 1966 a rn"5or operation was mounted in a 60 000 kmz zone at the intersection of the Mali, Burkina Faso and Ivory CoasE frontiers. Its financing was provided for by the European Development Fund (81, 219). Analysis of the results of these operations showed that control of the onchocerciasis vector was feasible over huge tracts of West Africa. A joint meeting of USAID, OCCGE and WHO was therefore held at Tunis, in JuIy 1968, to lay the foundations for a regional onchocerciasis control project. In pursuance of the meetingrs recomnendations (244) and at the request of seven VJest African States (Benin, Burkina Faso, Ghana, Ivory Coast, Mali, Niger and Togo), WHO and UNDP, held at Geneva in 1970 a further meeting which drew up the terms of reference of a mission, financed by UNDP, to work out a global strat.egy. The report of this Preparatory Assistance Mission to governments (PAG report) (245) was submitted for approval to the parEicipating African states, to potential donor countries and to the sponsoring technical agencies meeting in Accra at lhe end of 1973. Prior to EhaE., in April 1972, tt:.e executives of FAO, UNDP, World Bank and WHO had set up a Steering Comnittee to coordinate the planning and inplementation of the Prograrme. In January 1974 the report of the PAG mission rras approved. The budget required for launching the Onchocerciasis Control Progranune in Ehe Volta basin was voted. I{1lO was designated as executing agency. L.2 The managerial and implementaEion strgslqerqs elq !lC! An operational agreement concluded in 1973 between the participating governments and WHO deEermined the scope, objectives, and consultation and management structures of OCP together with the means by which the control operations and the evaluation procedures were to be conducted (241). 1.2.L Managerial strucEures The strucEures set up aE that tiroe consisted in: the National Onchocerciasis Conrmittees of the seven participating Statesi Benin, Burkina Faso, Ghana, Ivory Coast, Mali, Niger and Togo. They were responsible for liaison between Ehe national authorities and the Prograrune and establishing within their countries the requisite conditions for t,he successful conduct of operations. - Ihe Steering Conmittee, set up in L972, with responsibility for coordinating and sEeering the activities of the sponsoring agencies, IBRD, FAO, WHO and UNDP. - The Onchocerciasis TrusE Fund, set up in 1974, managed by IBRD and made up of contributions from the participating States and donors. ocP/84 .3 Page 14 - The Joint Coordinating Cormnittee (JCC) was the supreme body. Under the chairmanship of an independent notability, it consisted of representatives of the participating States, contributors and sponsoring agencies. Invested with supervisory powers over all the activities of the Prograrune, it was more specifically responsible for scrutinizing the plan of action and budget and for overall guidance. - Various advisory bodies: the Ecological Pane1, the Economic Development Advisory Panel, the Scientific Advisory Panel, and the Scientific and Technical Advisory Conunittee. In 1980 the institutional structures were remodelled (Fig. 4) (243). The JCC and the Steering Comuittee became respectively the Joint Prograrune Comnittee (JPC) whose Chairman is elected at each session, and the Corunittee of Sponsoring Agencies (CSe), with no major change in their functions. The Economic Development Advisory Pane1, the Scientific Advisory Panel and the Scientific and Technical Advisory Pane1 were dissolved and replaced by a twelve-member Expert Advisory Comnittee (EAC) wnose terms of reference covered the economic aspects of the Prograrmne. The functions of the five-member Ecological Group remained unchanged; one of its members sits on the EAC. No change was made to the National Onchocerciasis Comnittees and the Onchocerciasis Fund. L.2.2 Executing and support structures The executing structures (Fig. 5) come under the authority of the Programne Director; they comprise five units: Adninistration and Management, which handles personnel, finance and equipment, including transport and Ehe repair workshops. Epidemiological Evaluation, which al.so deals with the ophthalrnological aspecE. VecEor Control, which is by far Ehe largest unit and is responsible for aerial operations, entomological evaluation and applied research. Economic Development Unit. AEtached to the Office of the Director are the units responsible for public information, training and relations with public health bodies. Two liaison offices have been established, one at WHO|s headquarters in Geneva and Ehe other at its regional office in Brazzaville. To ensure rapid circulation of information OCP has equipped itself with an auEonomous radiotelephone comnunication system linking sectors and subsectors among themselves and also with the air bases and with the Prograruners headquarters at Ouagadougou. This system has proved extremely useful for rapid and rational planning of Ereatment schedules and their continuous readjustment to entomological situations. The radiotelephone is also used for logistic organization and for administration and personnel management. OCP avails itself of the computer at WHO headquarters aE Geneva to sEore the daEa collected by the entomological evaluation, epidemiological, ophthalmological and hydrobiological units. These consEiEute a unique corpus of information on onchocerciasis controL and epidemiology that can be consulted at any time. 1.3 Budge E and financing In the PAG mission report (245), the estimated budget for the 20 years of the programne wa,s 120 million United States dollars at the 1973 rate. The funding was planned for three per iod s . J ocP184.3 Page 15 t- I L Onchocerciasis Fund tBRD FIG. 4 ORGANIGRAM OF THE PROGRAMME L- I) Expert advisory Committee I t- TJ I -t IEcological .GrouPL National- -] Onchocerciasis Committees I IJ wHo 4t 322 Joint Programme Committee Committee of Sponsoring Agencies FAO, UNDP, WHO, IBRD World Health Organization Executing AgencY Programme Director ocP/84.3 page l6 o I o. ==AU ==-641-3ozUJ=o9(Ju ao F(5O2, :a=uEk= EEo =<cE5*5 =ofr : ci: s3E -aE(:t=<o=uiJg)o oouJ ES:F-< E== OC.)UG =<CUJo-o<uE ifiU ===dugoz,=d:H>- u)lU= ct J zGOEtr< sa EH c, ulc, o (J =o J 2 C' tr z. o u,UF -<FF v0O(:, uZ IIJ FF<FC EA =tr(5Eo< 4 F F6 U UzoN epP raa; J S=6e 9Eo? =a=>>uU J G UI otrlU' co N o tr GgJ4o G a .goccoo i uq.l E = -o C.J UJ = = GE a9oGq F =o o -r!(J =U C!'<o .^ cE =laE^'o= 2=9d z,r- o' -o'uJ<tsrt- =-o(J =UJF !: .D ctJ uJ(J L B c, 2, ctI J G q o(9 =c, cr U o = JF 6= aaOF =*u-.ioii L>u tll Z,J JO<-^-Lr=o(9:e J=UJ PEE 0s<EGU A G Eu>FoF <= F=(Eo 1lJ oLx u, J (J E 32o<FUI o' CE a J oo- EE 63 Gl(J UJ co E>EteE-E E:.9- 9E .c;.9.= E €f€'ic G('LFO EE6 UJ F ro gJ o rr o ct?u ,= iJJ < a9z. 3trto o7u J & o F CEoG v)z CEF =atr= suF<6z == E= Jul z. =oU'EUr J-6 <uJ CE (J DZZ!) =oc! o 6 e'^t=CJ=Or -(.J =o q9 E33ao= F utU =lu z. c,N JoGF =oF()= cE= c,F(J trJ GoF(J u,E6 ul = = e(9 oGG z, c, F Nz.><9(9E -AE<o -.E J=<3UJX -U c!J G,o = urBOE Jl-O - aa= 2.9 Il :;s! <;- J- = z uJ = = CE(9 o EG J o G,Fz'oQz 9uto<<.o6cGUJ lll \18;(9I< ->.\OO l!> o r.r.tFIcrF Eo J zIF N z 0 G, o ocP/84.3 Page 17 Funding period L974-t979 1980-198 5 1986-1993 Millions of dollars Total for period Annual cost 4L 5.8 to 8.5 34.5 5.6 to 5.8 44.5 5.6 The total expenditure by 1983 had exceeded the initial forecasts by approximately LZZ ia constanE dollars. Since OCP has extended its area of operations by 110 000 kmz and increased its expenditure for research on new insecticides and chemotherapy, it can be considered that the estimates have been kept to. At present, apart from the participatingStates, 19 countries or international organizations are contributing to the financing of the prograrntre3 Belgium, Canada, Federal Republic of Germany, France, Italy, Japan, Kuwait, Netherlands, Norway, Saudi Arabia, Switzerland, United Kingdoro, United StaEes of America, ADB, A1 Sabah Fund, OPEC, UNDP, IIIIO and t.he World Bank. Contributions are paid into the Onchocerciasis Trust Fund rnanaged by the World Bank. L.4 Strategy of OCP and delinitation of its area 1.4.1 Basic sErategy As there exists no drug active against the pathogen and usable in mass campaigns, the strategy of the Prograruoe was based on breaking the chain of Eransmission by destruction of the vector. Ihis is achieved by repeated insecticide treaEmenE of the fast-flowing reaches of the rivers where the larvae of S. damnoaum s.1. develo p. It was estimated that vector control alone would be sufficienE to interrupt transmission for a period longer than the parasitest lifespan, then evaluated at between 11 and 18 years (133). That was why operations were planned for a period of 20 years. Ttre ability of S. darurosuu s.1. to travel large distances in savanna zones was already known (195,230), buffiffiess of the progra*".."" (654 0oo km2) should, it. was thought, minimize the effects of penetraEion by blackfly from outside it. The strategy, mapped out in the report of the PAG mission, proved completely successful and has remained practically unchanged, whereas the tactics, particularly of aerial operations, and also the boundaries of the OCP area have been considerably modified. Two phenomena manifested by the vector, namely reinvasion and resisEance Eo insecticides, neceseitated these readjustuents. L.4.2 The OCP area L.4.2.1 Outline inforeaqiq! on phytogeographical zones and distribution of onchocerciasis and of its vectors in t,he participating States In llest Africa, and more particularly in the seven participating States, onchocerciasis is rife fron the Atlantic coast at latitude 5'N up to beyond the fourteenth parallel. The disease is therefore prevalent throughout Ivory Coast, Ghana, Togo and Benin and in three-quarters of the territory of Burkina Faso, only the norEhern part of which is free of it. In Niger, onchocerciasis is confined to the district of Say on the right bank of the Niger river. ltre disease occupies the entire southern parE of Mali, extending beyond the Niger river basin into the basin of the Senegal river. The area of dietribution of onchocerciasis in the seven participating States therefore forme a block, but that block is very heterogeneous from the phytogeographical viewpoint, with one zone of vegetation giving place to another proceeding northwards from the Atlantic Ocean to the Sahelian and Saharan regions (Fig. 6). Forest occupies rhe more humid parts neer the coast, in the Ivory Coast and Ghana; at its edges it shades into a mosaic of wooded patchee and savanna which is steadily lrnibblingt' the forest because of the exploitation of its resources and the developnent of farming. Then Ehere extends from the seventh to the ninth parallel a relatively humid open woodland zone; in eastern Ghana, Togo and Benin this type of vegetation covers more southerly regions and extends to the ocean; it separates the ocP/84.3 Page 18 west African forest block from Ehe central African one. Nort.h of parallel 8.5" humid savanna takes over, and then dry savanna stitl further north when the rainfall is below 850 tm. The distribution of blackfly belonging to the S. damnosum s.1. complex does not follow the pattern of the PhYtogeog raphical zones, though ffi"ch-influenced by climatic and ecolog ical features. The S. dimnosum s.s./s. sirbanum species pair occupies the savanna country up to beyond the fourteenth parallel. Ihe nor thern limit of its distribution is also the limit of onchocerciasis. BuE it extends far beyond the savanna country and into the forest along the main watercourses. The S. soub S. sancEi 1i species pair is of forest origin, but occupies the entire hum oPen zone penetrates here and there into the savanna uP to the tenth Paralle1. S. yahense is confined to small forest rratercourses. S. squamosum, which Probably comprises several entities, is widespread in forest and weE savanna counEry. S. damnosum s.1. complex, which The distribution of blackfly belonging to the will be considered in detail below (see section 5.2) has not rol operations, though the populations of cerEain species S. sirbanum ofEfrE s. a' been modified by the vector conE have been seriously attacked. 1.4.2.2 Est ablishine the limits of the OCP area Reference was made in the Introduction to the difference in severity between the blinding savanna onchocerciasis, associated with the Presence of llamrosYrn.."./ , and the relativelY benign forest onchocerciasis, associEted with other species annosum s.1. complex (see section 3.3). The initial limits of the OCP area were drawn uP to take in the nost serious foci of savanna onchocerciasis as far as known in 1975. Ihus they roughly correspond, in Ehe south, to the limit of the hurnid savanna zones except at the western and eastern ends where they veer northwards along the edge of t.he river basins. This boundary line Eakes advantage of the great dam reservoirs on the Vo1ta and Bandama (Lake Volta in Ghana and Lake Kossou in the Ivory Coast respectively), which eliminate the blackfly breeding sites over tens or hundreds of kilometres upstream, and in that respect those lakes could be considered as ecological barriers. This demarcation left out the more southerly onchocerciasis foci where the vecEors and parasites belonged at least in parE to savanna dwelling population (see section 3.3). The northern limit of the Programme coincided with t,hat of the area of distribution of the vectors and the disease. To the east and the west the limits of the Prograrrne area have no epidemiological or ecological justification; they coincide with Ehe frontiers of Nigeria in the east and Guinea in the west. In Mali, only thl part of the country located on the right bank of the river Niger was included in the Programme area, which thus formed a compact 654 000 km2 block, wh6se size was supposed to diminish the effects of any introduction of parasite vectors. Invasion of the Progranrne area by infective blackfly over much greater distances than foreseen led to a revision of the southern 1imit, all the more desirable in that some foci of severe onchocerciasis were not included in the area under treatmenE. The upshot. lras an extension of larvicidins over an additional 110 000 km2 in the Ivory Coast in 1979 and 26 000 k1n2 in 19801 and the preparaEion of projects for extension to the southern regions of Benin, Togo and Ghana which have been approved by the JPC and will be implemented as soon "" op"..iio.ril irrr".ticides fully utilizabll in those regions are availabLe (247,249,25L). The extension of vector control operations to the severe onchocerciasis foci of Senegal, Guinea, Guinea-Bissau and western Mali has been strongly recomnended by the advisory bodies Q73); one of its major spinoffs would be the elimination of reinvasion in the Ivory Coast and Uaii (see section 2.3.1). The JPC at its December 1983 session agreed to the financing of exploratory studies (256). The second evenE, or rather series of events, that has affected the Prograrmne is the development of resistance firsE to temephos and then to chlorphoxim (see section 2.3.2). The need for a change of inseccicides and application techniques has had major financial and operational repercussions which, so far, have been successfully coped with. 1 rhi" 26 ooo k*2 have been treated only from time to time. wP 184.3 Page 19 lrrctn ua e o .9q o =EtI € 4 ao - o oe E .9 = E o c F r; o oc co .E o G c !t € to .9 g o U .9t o E Ccca I o oB c o Eo x ; c a E E 66 G o 'E = I oco - .9o o o o o .9 ! cf oto I I I o o E & o =e ,E: o !o E, c tr P E)r cc 6 o \r r r r r UJ = = G(9 o TEE uJ IF o ct, UJ zoN o EA. G o o ul(, o tc ro (, lt i ffi -:=:=ff ocP/84.3 Page 20 1.5 Vector control operat ions It was evident from Ehe conclusions oPeration for control of S. damnosum s.1. of the Tunis meeting (Z++) ttrat a large-scale in West Africa must be based on application of larvicides by aircraft. 1.5.1 Selection of j-nsecticides and of methods and equipment for their application 1.5.1.1 Choice of insecticides The studies conducted under the EDF/OCCGE prograrune and the research done by the entomologists dgring the preparatory period demonstrated the very fine performances of tenephos (Abate(K/). h 20% emulsifiable concentrate at a dosage rate of 0.05 mg/Iitre/I0 minutes at high water time and 0.1 mg/litre/10 minutes in Ehe dry season it producis 1002 mortality in blackfly larvae. [JhaE is more, the effect is identical whether the entire dose of the product is released over 10 minutes from a boat or in a singte very brief discharge by aircraft provided that the total quantity of the product remains the same(12L, 204, 2O5, 220, 224, 225). This insecticide, a biodegradable organophosphorus compound had shown no toxic effect for ma*als or fish: its impact on the non-Earget fauna was moderate (see section 2.4). It was therefore pronounced acceptable by the Ecological Panel. Abate was the only insecticide used by OCP until 1979 inclusive and it is still applied in the major part of t.he Programne arear wherever the develoPment of resistance does noE necessitate its replacement. Where resisEance appeared in 1980 (see section 2.3.3), a 207" emulsifiable concentrate of chlorphoxim, anot.her organophosphorus compound, was used. Its performances are couparable to those of Abate but its toxicity for the non-target invertebrate fauna is higher. After the advent of dual resistance to temephos and to chlorphoxi. tPPe section 2.3.2) there was introduced into OCP a completely different preparaEion, Teknar\K/, I dispersible concentrate of Bacillus thuringiensis serotype H-14 (B.t. H-14), used at a concentration of 1.6ng/1it'"/ro@activeagainstb-Iackf1yIarvaeandhigh1yse1ective,so B.t. H-14 would represent an ideal product; but the only formulation at Present available lEr.rrt, such difficulties in utilization t.hat it can be regarded only as a last resort (see section 5.3). 1.5.1.2 Aircraft and equipmenE for larviciding The operational research conducted during the preparaEory period showed that helicoPters were required for treating the small watercourses fringed with forest galleries and also for pro"p."iions and checks on the effectiveness of treatment. Fixed-wing aircraft could be used ior treating the large rivers (22O,22L). These forecasEs proved valid for the application of chemical insecticides but not entirely so for treatment with Teknar. In fact, both the type of aircraft and Ehe larviciding equipment has to be chosen in consideration of the preparation to be used. (a) EquipmenE and aircraft for application of chemical larvicides Initially the equipment developed for releasing Abate in a single discharge h'as the system, based on a very simple principle, ca1led t'rapid releasett, which oPerates by gravity. ti req.rites preselection of the dose of insecricide to be applied (83,202)' At t.he period of high wat.er, to obtain a concentration equivalenf to 0.05 ng/litrl/rO minures ir is necessary to apply 0.15 litres of Abate per cubic metre of river discharge per second. Despite thl so*eiirol" r"ty high discharge raEes (several hundred ;3i;;":i rne ireatmenr can rhus be carried out by small helicopters with a pay-load of iOb tg or by fixed-wing aircraft of larger ."pr"ity-. The latter were equipped in addition "iit-i p,r*pi.rg device [har booscs Ehe pi""",rrl of the insecticides and enables quanEit'ies of beEween two and 50 litres of preparation to be discharged at a rate of 50 litres/second' In the dry season the quantity of Abate applied must be 0.3 licres p"t r3/.."ond of river dischargl in order to obtain a concenEr"tio.t of 0.1 mg/litres/l0 mn. But at that time ocP I 84.3 PaBe 2l of year flow rates are low, being rarely above a few cubic metres per second, and the quantities of preparat,ion to be diecharged at each release point are small. For this type of treatoent the helicopEers have been equipped with a pressure reduction system for the insecticide is pumped into the tank through a tube one metre long and 6 mm in diameter and then ejected with a discharge rate of 1 litre/second; quantities as small as 0.3 l-itre can thus be released. The piLot reduceg speed and applies the preparation in a t,ransverse swathe from one bank to the other, imediately upstream from each line of breeding sites. This gives a good distribution of the formulation in the river and overdoses harmful to the aquati.c fauna are obviated. The same kinds of equipment can be used for chlorphoxim. However, certain precautions must be taken for the preparation is corrosive and attacks Ehe larviciding apparatus. The helicopters are all equipped withttrapid release't and restrictor systems. Ttre fixed-wing aircrafE are equipped with Itrapid releaserr and pumps to boost the insecticide pressure. On the Turbo Thrush aircraft being tried out in the Programne a restrictor has been installed that enables the preparation to be applied in transverse swathes. (b) Equipment and aircraft for app lication of Bacillus thurineiensis H-14 Wtren formulations of Bacillus thuringiensis H-14 had to be applied, the situation changed radically. Ttre preparation used, Teknar, has the consistency of liquid mud. I.Ihen it is mixed with more t.han 502 of water and applied over a sufficient discharge tine, it gives satisfactory dispersion and carry. But when it is applied without prior dilution with a rapid release systeu on the aircraft, most of the active part.icles sink to the bottom of the river and there is no real carry. Prior addition of 202 of water has proved necessary for the fomulation to be useful in aerial treatment, but it still remains viscous and cannot be applied by gravity; it must be sprayed by a boour and nozzle system under high pressure mounted on the helicopter; a short boon 1.5-1.6 m in length, equipped with three to five nozzles, has been developed to give a discharge of 5 litres/second. It has thus been possible to use the preparation, but its carry and effectiveness are still not satisfactory. Moreover, in view of the 1ow content of active ingredient in the fornulaEions and the need to dilute them, the application rate has to be 1.2 lit.res of preparation per.3/""". of river flow. Because of the low emission rate of the nozzles and the substantial quantities of Teknar to be applied, it is out of the question to use fast, fixed-wing aircraft which pass over the breeding sites too quickly to apply to them the requisite quantities of insecticide for the treatnent. Finally, the low carry of the fornulation means there musE be a large number of release points. Only helicopters can therefore be ernployed at present. However, using the small ones in service in the Prograr"'ne, with a 200 kg payload, only rivers with flow rates belorr 50 nJ/second can be treated. Teknar treatnent of rivers with high discharge rates is not only very expensive but necesgitates using large helicopters. lherefore, a Be11 204 helicopter equipped with Ewo 600 litre storage tanks and a boom and tozzle system was added to the contracting companyts aerial fleet in 1983. L.5.2 Execution of vector control operations L.5.2.1 Phasing of operations The operations were preceded by inventorying and mapping of aI1 larval habitats of S. daurosum s.1. in the dry and high lraEer seesons. It proved possible to carry out this enorEous t rapidly by organizing prospecEions from helicopters that gave access to river streEches wtrich could not be reached over land. The initial Prograrune area rras divided into three zones where the conmencement of larviciding took place in three successive phases staggered over tlro years (Table 1 and Fig. 7). [szert oua ocP 184 .3 page 22 @r € \ \ T il -ll!\) oz o E UJ o.o (9 z 6 C)tE Ll,l J- lt o rD UJ v, I o- ct, z UJ G IIJItlt 6 UJ - q, l! I .E o, .E o E 0c o 0co xo o .= .E I o c o E i\N E Y o o o @ o cn LlJ ; cn - G -,.r1 '!L\\ t-I\_\rL o ^o -* o' loi- lFt z o U' z ]U x UJ z G, UJ D o U) I --ol)e,Y I I l.i ( ol E Y o o o tt (D t.; o - A. uJ an a- N E Y o o o lc ot t- I !. --\ a _-) ol t Y o o o @ (o IJI v, I o. = uJ ch I o- 1r, lu = -t !' l J,- w ,,.*g_ cAq .i E Y o o o (_ t,-rr- ) ocP I 84.3 Pege 23 TABLE 1. TIMETABLE OF TTIE VARIOUS PIIASES, AREAS AND LENGTHS OF RIVER UNDER TREATMENT * Based on Walsh, Davies & Le Berre, 1979 (178) and updated in 1984. Larviciding r{ras started in phase I in February L975 afEer the first contrecting aerial company had established its base at Bobo-Dioulasso, Burkina Faso, in October 1974. The zone t.reated during this phase comprised the western part of Burkina Faso, the northern part of the Ivory Coast, Ehe eastern fringe of Mali and the north-western fringe of Ghana. ring phase II, beginning in January 1976, operations rrere extended to the White Volta and Red Volta basins in Burkina Faso and northern Gtrana. By March L977 Latviciding covered eastern Mali as far as the river Niger and the north-L,est.ern Ivory Coast (phase III west) Eogether with the focus in Niger, northern Togo and northern Benin (phase III east). This brought the 654 000 km2 of the initial Prograrune area under t,reatment. Vect.or control was extended to the greaEer part of the Ivory Coast in April 1978 in execuEion of phase IV and Ehe lower Como6 came under treatment in 1980. L.5.2.2 Aerial fleeE and ground support At the very start of the Prograrune it was decided that the aerial larviciding operations would be subcontracEed to an aerial company which would also take responsibility ac the Prograruners request, for transport of staff on prospection or inspection assignments. The subcontracts would be awarded afEer advertising the requirements and the wide circulation of an invitation to bid. The initial contract in 1974 was concluded wich Evergreen Helicopters, Inc., a United States company employing a fleet of Pilatus Porter aeroplanes and Bel1 206 B helicopt,ers, based at the Bobo-Dioulasso airport. Tn 1977 the conE.racE was taken over by the Canadian company Viking Helicopters Ltd., with which it was renewed in 1980 and 1983. Its fleet, half of which was stationed at. the Bobo-Dioulasso airport in Burkina Faso and half at the Iamale airport., Ghana, consisted oftwo Pilatus Porter aeroplanes and eight Hughes 500C helicopters, replaced in 1983 by the Zone Date monitoring started Date larviciding started Areas treated in 1 000 km2 Maximum length of watercouraes t.reated in km2 Phase I Phase II Phase III West Phase III East August 1974 June 1975 June 1975 June 1975 February 1975 March 1976 March 1977 July I977 247 r34 77 L96 4 800 2 575 3 150 6 450 Initial area treated 654 15 175 Phase IV Ivory Coast March 1977 April 1978 March 1980 110 26 3 500 L75 Maximum area treated 790 t8 850 Southern extension study zone June 1978 UnEreated until 1984 111 5 830 ocP/84.3 Page 24 higher-performance Hughes 500D model. In 1983 the Be11 204 helicopter, stationed at Bobo-Dioulasso. con'mission in 1983 t.o replace the Pilatus PorEer. transferred to Kara, in Togo. fleet was supplemented by a large capacity A Turbo lhrush aeroplane was also put into In December 1982 the Tamale base was The aerial operations constitute a large-scale logistic exercise. SevenEy improvised heliport.s and more than 100 fuel and insecticide storage depots have been established over the whole Prograrmne area. Keeping these depoEs supplied has to be carefully planned, for 11any cannot be reached by road in the rainy season. If insufficient supplies are delivered to ihem, the aircraft have t,o make much longer trips between treatment points and well-stocked depots and carry a large reserve of fuel at the exPense of insecticide. At the saoe time, however, stocks of insecticide cannot be left Eoo long at the depots for fear of deter iorat ion. 1.5.2.3 Periodicity of larvicid and sites of application The larval stage of S. damnosum varies in length according to the temPerature of the rrater. In the OCP area iE r."g"" from 7 to 12 days; development of the species is continuous throughout the entire period at which the habitats are functioning, and the generations overlap (see section 5.2.). I{eekly treatment of the breeding sites has therefore been made the basis for the control ofthevector.Thisperiodicityp.""1.,d".any@1arvafromreachingthenympha1 "a.g", at which it wouta no longei be vulneraUfE, ana-is extremely convenienE for Ehe planning of treatment circuits. In the lorrwater season one line of breeding sites is separated from Ehe next by stretches of sEagnant water that the wave of insecticide cannoE cross. The treatment must it"."fo.. be cariied out site by site, the insecticide being applied in a transverse swathe upstream from each breeding site. At high-water season there are continuous lines of breeding places all along the \ratercouraes, which have few or no stagnant reaches. Starting from iCs point of application the insectici-ae forms an effective ttrdavet'over varying disEances depending on the formulation. Itris ttcarrytt of the larvicide may exceed 40 km for Abate; it is much shorter, probably less than 5 km, for Teknar. To obEain complete "coveragett of a watercourse an application of Abate must be made every 40 kn or an application of Teknar at least every 5 km' L.5.2.4 Organi zat.ion of weekly treaEmenEs The weekly treatments are organized in consideration of the entomological data, r'hich determine their conEinuation, susPension, or resumption on a given river sysEem' The qrr..rtity of insecticide is calculated from the gauge readings by which the discharge rates of the watercourses can be calculated. These readings are taken during the week preceding the t.reatment. However, at some seasons there may be considerable variations in discharge rate within a few days, in which case the readings no longer correspond to the discharge rate on the day of treatment, leading to under- or over-dosages. To cope with this problem OCP is going to try oug the potentiilities of a network for Eeletransmission of hydrometric data by i.goI beacons relayed'by satellite (276). The oti basin in Togo has been chosen as pilot zone and the trials began in August 1984' A sumary of the resulEs of entomological surveillance and Ehe gauge readings are transmitted aE the end of each week to t.he aerial oPerations bases and Ehe Vector Control Unit (VCU) headquarEers. The aerial operations officers calculate the discharge of the rivers and the quantit.ies of insecticide to be applied at each release point. Treatment maPs are prepared for each aircraft, showing the Ereatment circuit together with the fuel supply ;;i";" and stopping places for the nigf,t. Under.ideal conditions, the exact position of each application point Is'entered on the rnlp, though it is sometimes necessary to leave the pilot a certain latitude. on Monday afternoon, the aerial oPerations officers give instructions Eo the piloEs. on Tuesday at dawn the treaimenE aircraft leaves its base for a circuir generally taking three-days. On his return each pilot rePorts on his work and conmtunicates his observations. ocP/84.3 Page 25 Every Monday morning, the VCU authorities have a radiotelephone conversation with t.he zone, sector and subsector chiefs and with the aerial operations controllers. In the light of this t'briefing", decisions are taken on extension or reduction of treatments in certain regions, any changes of insecticicide and, more generally, all measures to be taken with regard to vector control. Ttrese instructions are transmitted to the aerial operations officers who are responsible for having them carried out. 1.5.2.5 Larvicidins from the ground Some isotated breeding places very remote from the aerial treatment circuits may be treated from the ground or the river. Most of these habitats are on rrat.ercourses with lowdischarge rates (e.g. the Nigerian tributaries of the Niger, the loop of the Black volta inBurkina Faso, artificial habitats in the Dogon region of Mali, etc.). But in Mali certainisolated breeding sites on t.he Niger (e.g. Markala and Tienfala) where Ehe dry season flow rate is above 100 nJ/sec. are also treated by boat. Sometimes treatment from the ground has been used to make up for shortcomings in aerial treaEment.s when the breeding places were accessible. This latter type of intervention is becoming increasingly rare. Several methods of application are used. Ttre simplest consists in nixing at the river's edge the requisite dose of Abate (on the basis of 0.1 urElLlLO mr) with uater in a bucket. and throrring the preparation into Ehe watercourae. Since 1983 the preparation has also been applied with a Iludson sprayer with a high-discharge conicaL tozzl.e whose jet carries to over 10 metresr so that habitats can be treated where there is no access to the rraterrs edge.Finally, on the Niger, a mixture of Abate and water is released from a drum carried on aboat; the boat's screw churns this nixture into t.he river water. It must be stressed that treatmenE from the ground represents a Einy part - far below LZ - of all the Programefs vector conErol operations. Only Abate has been used in this type of treatment. L.5.2.6 The Iextentt'of treatment At present larviciding is carried out over an area of 754 OO0 km2 occupied by over 15 million people. In the high water season the number of kilornetres of river under effective treatment may reach 18 000, but in general ir remains well below rhat ceiling (rig.8A). In the dry season many rratercourses dry up. Moreover, on those rivers which conEinue toflow larviciding is interrupted when the entonological situation perrniEs, i.e. when entomological moniEoring detects no (or very few) blackfly. The number of kilometres of watercourse under treatnent then falls below 4000 (161) and was even down Eo less than 600 in March 1983 (Fig. 88). There are considerable variations in flow rat.e from one year to another in the same season. Figures were particularly below normal in 1983. The cost of vector control does not diminish proporcionately to the reduction in the number of kilometres of river treated, as in the dry season each breeding place must be treated separately so there have to be more release points. L.5.2.7 Evolution of vector control tactics in OCP Until 1979 Abate(R) ro." the only insecticide used by the Progranrne. Its high effectiveness and ease of application enabled all watercourses, inctuding Ehose wiEh highflow rates, to be treated. Extensions of the OCP area could thus be envisaged without iear of encountering major technical problems. The advent of resistance disrupted this smooth functioning and the Prograrsne had Eo readjust its vector control tactics and methods so as to cope with the problems that arose.In 1980, when resistance to tenephos appeared in the S. soubrense/ S . sanc t ipaul i populat ions of the southern Ivory Coast (68) , the only replacement larvicide available was chlorphoxim, which was applied at a dosage rate of 0.025 'r,glllLO rrr, and t.hen at the same dosages as Abage on all breeding sites as and when resistance became apparent. Ihe greater part of the FIG. 8A MAXIMUM EXTENSION OF AERIAL LARVICIDING IN AUGUST 1980 Yft= #-, ocP/84.3 page 26 c ( I i L\ I - Abotc . r.. .... Chlorphoxim FIG. 8B AERIAL LARVICIDING REDUCED TO MINIMUM, ENO OF APRIL 1983t-_ft- o ( I ( o3 -+ -?- .+-' Deliberate suspension for trials of ncw larvicides t) I I I J C- Teknar ocP/84 .3 Page 27 phase IV zone was thus treated during the 1981 rainy aeason. But the onset of resistance to chlorphoxin (201) necessitated a further tactical adjustment in 1982. In the zone of dual resistance in the Ivory , were treated with Teknar large rivers cont, S. damnosurn'/ S. si inued t rbanum s ,a .most down to th 9gq"t, during the 1982 dry season, rivers with medium discharge rates\A/, e formulation of B.t. H-14, while the lower reaches of Ehe o be treated with Abate to destroy the savanna species whose area of distribution in forest country extends far to the e ocean, and to prevent them from reinvading the more northerly zones. During the 1982 rainy Beaaon the reappearance in some Ivory Coast. regions of normal susceptibility to chlorphoxira in S. soubrense/S. sanctipauli permitted the experimental use ofthis-preparationoncertainreffiattheendoftherainyseason. Teknar\K/ was applied only to wat.ercourses with discharge rates below 5o m3/slcond, which Iras the lirnit of the treatment capacity of the helicopters then in service (in future utilization of the Bel1 204 helicopter will uake it possible to operate on rivers vrith_higher flow rates). lhe lower reaches of the large rivers continued to Le treated ,igh 45.g.(R) as did certain savanna zones (Bui, upper Bandama) where S. soubrense/S. sanctipauli and S damnosum/S. sirbanum developed in conj unction: the target here was of course only thelatter spec sPa r. At the beginning of 1983 the demonstrat.ion of reduced susceptibilicy to temephos in the savanna species S. daurosuu/S. sirbanum on thg_[ower Bandama gave a serious warning to theProgramemanage@456gg(R)wasirunediatI1ysuspendedovertheentire river basin and intensive treatments with Teknar were instituted on the lower reaches. The exceptionally low discharge rate of the Bandama, which was still below 10 m3/second at thebeginning of September, enabled this preparation to be used throughout the rainy season. The ain of this operation was to rrclean up" the breeding places of resistant larvae and neutralize an enormous blackfly reservoir. On the rest of the Ivory Coast river system Teknar and chlorphoxim were used in turn, utilizing the experience acquired on the Marahouein 1982. Reinforced entomological monitoring has demonstrated the high quality of Ehe results obtained, since the number of biting females has remained very low to dat.e. The rest of the Progratme area where there are no resistant populations is continuing to be treated with Abate. The outlook for vector control in future depends on the development of new insecticides or new fonnulations, in particular of B.t. H-14, to neutralize any development of resisEance in the savanna species. Meanwhile the Expert Advisory Comittee has recormended (273) that no sout.hward extension should be undertaken until replacement insecticides are available and operational. With this in view the Programe, jointly with its partners, is conducEing ongoing research for the development of new larvicides (see section 5.3.). 1.5.2.8 Insecticide consumption and number of fli ght hours These date are given in Table 2 as an indication. The quantities of Teknar used by OCP are very large, though the use of this preparation is applied only to certain rivers in the Ivory Coast. This is due to the dual consEraint: the need to use large doses and to increase the number of application points on the largest watercourses. In the rainy season it takes 15 to 20 times as much Teknar as Abate to treat the same stretch of watercourse. Ttrough the price of the preparation is less than half that of Abate, the toEal cost of larviciding with Teknar is much higher. In the dry season the difference is admittedly smaller but the major part of the insecticide consumption takes place in the high water season. The number of helicopter and aeroplane flight hours has varied 1ittle except in 1983, when the tempo of control operations was reduced because of the drought condit.ions. However, whereas during the first trro years nearly 302 of helicopter flight time and LO% of. aeroplane time was devoted to prospections, from 1980 onwards this activity accounted for only lO7" of.helicopter flying time and aeroplanes were no longer used in it. ocP/84.3 Page 28 The aerial fleet is fuIly employed only for three months a year at high-water season and definitely underemployed during the dry season, but the aircraft mu6t sEay in the Progrannne area all th. ye.r round. The aerial contracE guaranEees the subcontracEing comPany a certain number of flight hours per year, the hours which are not ttconsumedt' in Ehe dry season being carried over to the high-water period. TABLE 2. INSECTICIDE CONSUMPTION AND FLIGHT HOURS IN OCP * Expressed in litres of marketed preparation. L97 5 L97 6 L97 7 L978 L979 1980 198 1 L982 1983 Consumption of larvic ides AbaEe C200* Chlorphoxim Teknar Flight hours He 1 ic opter s Aeroplane s 75 63L 2 783 54L L29 947 4 265 6t4 155 615 5 358 I 025 2t5 879 5 286 L 204 263 377 5 504 L 37L L84 5L7 5 7L3 4L6 5 752 r 056 130 000 70 000 1 500 5 000 | 025 L62 750 6 699 232 986 5 689 966 74 807 35 796 310 000 4 9L5 500 ocP 184.3 Pege 29 2 2 CHAPTER II OVERALL RXSULTS AND PROBLEMS ENCOUNTERED IN BI.ACKFLY CONTROL Vector control being the cornerstone of its strategy, the Programe established from its inception an entomological evaluation netrdork to keep a continuous check on the effectiveness of aerial operations and detect any shortcomings in them. After nine years it is possible to follow up the development of the operaEions, analyse the problems they have run inEo and, finally, take sEock of their gIobal impact on the vectors. This same time lapse enables us to evaluate the effect, in the medium term, of repeated insecticide applications on the environment and in particular on the river fauna, thus fulfilling the objectives of the Ecological Groups. .1 Entomological surveillance 1.1 Purpose of surveillance Entonological evaluation began, before operations were launched, with exhausEive inventorying of the larval habitats of S. daurosum and collection of baseline data on the identity of the species of the complex, various endemic zones of the OCP area. biting rates and transmission pot,entials in Ehe Since the st,art of operations it has provided weekly quantitative and qualitative information on blackfly populations and onchocerciasis transmission. Consequently, it enables t,he detection of any substantial local production of blackfly due to treatment failures or to resist.ance and any exogenous input of blackfly. In the light of the findings of thie entomological surveillance, larviciding is reduced or even suspended in regione where there are no blackfly. Where, on the other hand, there is local production of flies, it is stepped up and adapted according to their identity and characteristics (see section 2.L.4). 2.L.2 The entomoloeical surveillance network Entomological surveillance is one of the Prograrmets main activities, assigned to the vector control unit (VCU). It covers Ehe entire OCP area, which has been divided into seven sectors subdivided in turn into subsectors. These last, numbering 24, constitute the basic cells of the entomological monitoring network. Each sector is directed by a qualified entomologist with a University degree who has had specialized training in blackfly control. The subsecEor chiefs are specialized technicians who direct three or four teams of two capturers, each provided with a driver and an all-purpose vehicle. The teams perform the weekly or fortnightly capiures of adult blackfly and bring them alive to subsector headquarters. They also take the river gauge readings and collect meteorological data. The subsector chiefs supervise the teams, collecting, recording and transmitting theirdata. Ttrey identify, to the extent poesible, by species the blackfly captured and dissect a certain number of them in search of infective larvae (1,3) in the fliest heads. They perform the weekly larval inspections at checkpoints. Owing, however, to t.he difficulty and danger of collecEing larvae, especially in the high-water season, only the positive findings at alimited number of sites can be recorded. In addition, the subsector chiefs carry out thelarviciding of certain habitats (see eection 1.5.2). Lastly, they undertake surfrary monitoring of the environment, note any abnormal mortaliEy in fish or other aquat.ic fauna, and obtain informat.ion on utilization of pesticides in agriculture or for fishing. They maybe called upon to assist in certain research. Some 670 entomological checkpoints (table 3) were selected during the pre_operationalphase. They were chosen, in general, from among the sites where biting and transmission retes were very high, i.e. where conditions were the worst in the progiarure area. Account ocP/84.3 Page 30 was also taken of their accessibility and, as far as possible, of their proximity to villages selected for epidemiological evaluation. The entire Programme area was thus under surveillance. TABLE 3. ENTOMOLOGICAL MONITORING POINTS the placed Sec Eor Subsector Larval monitoring point s Adult blackfly capture po int s Total monitor ing points I^Ieekly Fortnight 1y BOBO-DIOI'LASSO Bobo-Dioulasso Diebougou 42 22 5 2 8 5 55 29 OUAGA.DOUGOU Ouagadougou Niamey 40 11 5 3 L2 4 57 18 BAMAKO Bamako Bougouni/Kout iala Sikasso/Band iagara 9 4 32 9 4 5 7 11 l5 I9 19 52 BOUAKE Bouake Korhogo Bondoukou Od ienne Seguela 25 33 20 28 11 4 3 3 2 3 7 8 10 7 10 36 44 33 37 24 TAMALE Tamale BolgaEanga Hohoe Kintampo 15 11 5 18 8 6 6 3 9 8 8 8 32 25 19 29 KARA Kara Dapaon Atakpame 20 11 11 4 4 3 10 7 13 34 22 27 PARAKOU Parakou Nat it ingou Kandi Bohicon 5 9 7 5 2 6 3 3 5 7 4 3 L2 22 t4 11 7 23 394 90 186 670 ocP 184 .3 Page 31 Ttris entomological surveillance network hes funct.ioned admirably during Ehe 10 yearsthat have elapsed and has fulfilled to perfection the role assigned to it. It is, however, cunbroue and costly to oPerate. It is Eherefore planned to slim it down in anticipation ofthe gradual transfer of part of its activities to the participating States, wheneverincreasing stretches of the Prograune area are no longer under threat of resumed transmission. Certain subsectors have already been abolished in the zones where the entomlogical and epideniological situation is highly satisfactory, such as the central partof Burkina Faso. Ttre introduction of new nonitoring methods is aiso under study. But anyinnovation is conditional upon maintaining a high standerd of evaluation so that any recrudescence of blackflies can be detect.ed. 2.L.3 Collection of entomological data The collection of adult blackflies is perforned by hired capturers posted at the selected checkpoints; they collect the biting females which alight on them before they havehad tine to bite. Catching lasts from 7 a.E. to 6 p.r. and enables the daily biting r-.t" tobe determined. Each fly is collected and kept alive in an individual vial for subsequentidentification and possible dissection. At the end of the day the blackflies are dispatchedto the subsector with the form on ntrich are entered the toEal number of flies captured by theteen' recorded hour by hour, the results of the search for preadult stages, and the rivei geuge readings. At the subsector laboratory identification of females be longing t.o theS. demogum couplex, on the basis of morphological criteria, is undertaken when possible. In the rreetern Programe area this involves separating, according to the colour of the wingtufte, the feoales belonging to the species pair S. damrosum s.s. S. sirbanum from those belonging to the species S. soubrense/S. sancti paul In the eestern part of the Progranme area this criterion is not applicable (58, 78). The identification by species of adultblackflies of the S. darurosum complex has posed and is still posing serious problems. Indoubtful cases recourse must e had to cytotaxonomic study of the larvae produced by the captured females. Ttris task is of course beyond the competence of the subsector staff (see section 5.2.1). A proportion of the captured females, constituting a representative sample of the catches, is dissected at the subsector laboratory to determine the parous rate and look forthe developmental stages of Onchocerca volvulus, particularly the infective larvae which are to be found in the head Ttre main purpose of identifying the blackfly larvae and pupae collected during prospections of breeding sites is to separate Ehose belonging to the S. darurosum complex from embers of other species such as S. hargreavesi and s. griseicolle, c6G6i-ffie prograrEtre area but not inplicated in the transmissi on of onchocerciasis. Finally, the Eaterial collected in the subsectors can be utilized norphological studies. for cytotaxonomic and 2.1.4 Utilization of entomological surveillance data. EstablishmenE of entomological indices Confirued absence has been successful. of blackfly is of course the incontrovertible sign that vector control A high blackfly count can have two possible explanations: (a) local production, in wtrich case nulliparous females account for a high proportion of the caPtures made on man and larvae are found in the watercourse. Such local production may result from shortcominge in treatment or resistance in the blackflies to the insecticide utilized; (b) an invasion of females, sometimes from distant sources (see section 2.3.I), in wtrich case the fem,les captured on man are practically all parous (52). Ttre density of the blackflies present at a site and the intensity of the potential tranemieeion at that sane site are quantified by two indices: the annual biting rate (ABR) and the annual tranemigsion potential. (ATP), wtrich are esEablished from Ehe data collected bythe entooological evaluation netrrork (38, 164). ocP I 84.3 Page 32 2.L.4.1 DefiniEion of ABR and ATP The annual biting rate is the theoretical total number of bites that would be received by a person stationed 11 hours per day at the capture point in one year. It is calculated by .iai"! the monthly biting rat.es established fron the catches made at each point by the staff of rhe subsectors (2L4). ,tential is the theoreEical estimate of the total number of ble from O. volvulus that would be received by a subjecE in one year. It 1S eA tablished by adding the monthly transmission potentials (Utp), calculated by a very simple formula (213): The annual transmission po infective larvae indistinguisha sEationed at the capture point Number of days in month Number of infective larvae Number of blackfly captured x I'ITP = Number of catching days llum6er-E-1aEf 1y d issected While Ehe first of Ehese indices is purely entomological, the second has very considerable epidemiological significance, for its values can be related to the levels of endemicity of the disease (see section 3.2). NoEe that for caclulating the ATP only Ehe infective larvae found in the heads of the blackflies have been taken into accountr this method of calculation having proved statistically satisfactory (213). 2.L.4.2 The utility of ABR and ATP for assess].ng the entomological situation The ABR and ATP figures quantify the biting activity of blackflies and the disease transmission for an individual stationed at a specific point generally chosen because it is representative of the most dangerous conditions prevailing in the region. But iE is not a measure of the real number of bites or infective Onchocerca larvae Eo which the inhabitanEs of the region are exposed (237). This is because the population move around in a composite space where ABR and ATP vary considerably from one place to another. Ttre indices diroinish with increasing distance from the lines of breeding sires, particularly if there are villages in between; this finding also applies to zones of reinvasion, where there is little dispersion of the blackfly frorn the sites where they lay their eggs. Furthermore, villages exert an avoidance effect on blackfIy. Lastly, density of human population ttdilutest'the number of bites (see section 4.2). The theoretical ABR and ATP calculated from the findings of entomological surveillance are therefore far higher than the biting activity to which the local populaEion are effectively subjected. It would of course be possible to calculate the quanEity of transmission affecting each fraction of the population by analysing the time it spends in each part of its area of activity and measuring the ABR and ATP in each of them. It would be an interesting research undertaking, but a rather considerable one, since each comnunity has a part.icular situaEion in relation to the river, occupies space in a way specific to it, and has its own lifestyles and work patterns (see section 4.2). Despite all these reservaEions, ABR and ATP remain good comparative indicators of the entomological situation; Ehey are Che basic tools for evaluation of the results of vector conErol in OCP (164). The ABR and ATP vary considerably from one year to another depending on hydrological conditions and it is reconmended by the ophthalmologists that a mean ATP be established over five years (154), since the clinical manifestations of onchocerciasis are the result of infections accumulated during several years of transmission. x ocPl84.3 Psge 33 2.L.4.3 Relationships between ATP and ABR During the pre-operational phase in Burkina Faso the ratio between ATP and ABR sas generally 1 to 10 for the S. dalrrosum/S. sirbanum pair. In Ehe Volta region of Ghana it wae l to 20. At certain places in southern Benin ABRs of 35 000 are accornpanied by alrcet zero ATPs, but in this latter case it involved. For these two species is mainly the S. soubrense/S. sanctipauli group wtrich 1a the ATP-ABR ratio in the Ivory Coast ie I to 50 (232). Irlhen savanna and forest blackfly coexiet, ea at the Bui Rapids in Ghana, for eraple, it has been found that S. damnosum/S. sirbanum transmite 2.5 times as many infective O. volvulua as S. eoub S. sancti li, for the same number of paroue femaleg. In effectively treated zones the ratio ffi a"rrd" to diminishl this is wtrat hae happened in the Prograrme area as a whole (Fig. 9). Ilowever, this ratio, after shoving a fall, has risen again to its starting 1evel in places wtrere difficulties have beear encountered in larvicidingr e.g. on the Sissili in Grana (237). The number of infective larvae per thousand blackfly diseected has been taken as an index of effectiveness of transmission (237). It reflects Ehe ratios betrreen ATP aud ABR. This index has not been utilized in the operations of the Progranme. 2.2 Overall results of vector control 2.2.L Framework for interpretation: the OCP operational zones (OOZ) Ttre Prograrme area is very heterogeneous, both from the clinatic and phytogeographical viewpoint.s and with respect to Ehe variety of blackfly species and their susceptibility to insecticides. Moreover, its marginal zones are more exposed than the central parts Eo invaeion or simple infiltration of flies from outside. This variety of eituations accountg for the uneven resul-ts of vector control, excellent in some zonea, less good in othere. In the planning of a long.term strategy the measurea to be taken in the varioue OCp zones are conditioned by the problems encountered in vector control. The Prograrme area andits proposed extensions have therefore been divided up into operational zones (oozg) (275). Ttris framework, based essentially on entomological data, has been used for the planning of Programne activities, and is followed in this report for interpreting not only the results of vector control but also the ensuing Erends in the epideniological and ophthalmoLogical s ituat ions . OOZ 01 comprises Niger, north-western Benin, the whole of Burkina Faso (except the loser Black Volca and Bougouriba basin together with the upper reaches of the Cooo6 and Leraba), and eastern MaIi. @Z OZ comprises south-rrestern Burkina Faso, norEh-western Ghana and the north-caaternIvory Coast, consisting eseentially of the upper Como6 basin and the niddle Black Volta baeia. OOZ 03 comprises t.he Malian part of the Progranme area to the sest of the river Niger and the northrrestern parE of the Ivory Coast. OOZ 04 includes the central part of the Ivory Coast except for the middle Cono6 basin and the tributaries of the Black Volta. ooz 05 comprises the southern part of the Ivory coest and the lower Black Volta besin in Ghana The whole of OOZ 06 is in north-eastern Benin. OOZ 07 is constituted by the south-easEern flank of and north-eastern Ghana. the PrograrrDe area in Benin, Togo OOZ 08 extends over Ghana north of Lake Volta and over northern Togo into the north-nestern pert of Benin. ooz 09 rePresents the southern extension zone in Benin, Togo and south-eastern Ghana. The boundaries of ooz 10 would be those of the rrestern exEension aree. ocP/84.3 PaSe 34 4000 CoMPARATIVE ff* RATIOS lN PROGRAMME AREA AS A wHOLE (A) Prior to operations, 1975 included FIG.9 32000 48000 Annual biting rate (B ) Resultat from Nov. 81 to Oct. 82 a 30 40 s0 Annual biting rate All sites with an ABR above 1000 or an ATP above 100 3000 c o 6 .E oc(u E =cc 1 a000 0 a o i ataa a 0 64000 8000016000 4000 3000 2000 1000 G cq) o o. c o 'E 6c(E L (! fcc a 8070200 a Rr ? :a0 10 60 ocP/84 .3 Page 35 I .t !. I o o I .t o l.i l. I t. t I I3. a att' .ll ( .e@i I t i \ ,,F. \ + -fr- GN oI o ut z oN J z o CEuac ?!u = =t c!,:- "l-l c \ ocP 184.3 pa8e 36 2.2.2 The situation pr ior to operations Fig. 11A and Table 4 show that, before operations began, 56 capture points had an ATP of over g00 and were therefore rated hyperendemic, 35 had an ATP ranging frou 800 down to 100, and only t had an ATP below 100, i.e. considered as tolerable. These ATp values, est.ablished during two years of particularly low river discharge, 1973 and 1974, are far below the mean values of that index at the same sites during the 1960s, as reported by OCCGE at the time. 2.2.3 The entomolog ical situation in 1983 From the very start of larviciding the results lrere sPectacular. In 1976 the ATP was already below 100 at 65 capt.ure points and above 800 in only two (faUte 4). By 1983 the situation had improved still further (Fig' 10B)l the ATP was below 100 at g5 of the capture poinEs and above 800 at only one (Table 4). Referred spatially to the OOZs these data bring out the following facts: - results have been excellent in OOZs 01r 02 and 08; - results have been less good in OOZ 03, which has been reinvaded by blackflies from sources outside the OCP areal - in OOZ 04 the problern is the same as in OOZ 03, but is complicated by resistance to organophosphates in S. soubrense S. sancti auli and results are uneven; - the results in OOZ 05, where resistance to organoPhosphates affects the most abundant species, are di S. soubrense/S. fficult to interpret so long as sanctipauli has not been clear1 the epideniolog y established ( ical role of see section 3.2); - in OOZ 06, high ATPs have been recorded; it has not yet been possible to determine whether this was due go reinvasion by exogenous blackflies or to flies breeding loca1ly; - OOZ 07 is subject to reinvasion and infiltration of blackflies originating from untreated regions and high ATPs have been recorded Ehere. To sum up, vector control is giving excellent results from the entomological viewpoint(efp<100) in more Ehan 857. of rhe catching points in Ehe initial PrograEme area (fig. 111). High transmission rates (efp>400) persist in less than 5% of. thaE area. Where results are .rol frrlly satisfactory the causes reside partly in the difficulty of treating certain habitats (the Bui zone on the Black Volta, the Kulpawn iu Ghana, certain rivers of the Atacora in Benin and of the Kara basin in Togo, for example), but above all in reinvasion on the outskirts of the Progrartrne area and the development of resistance in the Ivory Coast. NoEe that in the zones "rb3."t to reinvasion only those villages located alongside thewatercourses are rea1ly affected, which reduces the epidemiological impact of the phenomenon. Operationally, resistance has hitherto involved only i. soubrense/S. sanctip , mainly in the regions which had not been included within the ograme area. 2.3 Problems faced in vector control Vector control has had Eo face two obstacles: invasion of treated zones by nigrant blackfly coming from untreated rivers, referred to as the reinvasion phenomenon' and the advent of resistance to insecticides. ocP/84.3 PaEe 37 FIG. 1.IA ANNUAL TRANSMISSION POTENTIALS PRIOR TO OPERATIONS ATP Q .roo O roo-rss O zoo - sss Q +oo -zss J - eoo ),, I i \Je-' -__--\., II o - Lrmit of Programme Southern extension I I \ I ( ) ATP O'too Q roo-rss Q zoo-ass Q roo-zss O.eoo FIG. 118 ANNUAL TRANSMISSION POTENTIALS NOV. 82 - OCT. 83 oo o o -l a-l'- , '_{16'I ,) x o l o Limit of Programme t + + +\ lnitial limit of Programme --- Southern extension 7\ \ l- -:u,- * ib ) \\ \i \ t ) r_\ -.t I :t ''' :7 an @ IN @ r-tca# @ a CN N @ Ii cO o\ aO\L^-f N o\ co I co coro\cac.)N NC\ @ I o\r rnrno.J\O ri roN r I @ r @O\\ONr o{ @r IN r Co\@N i N rr I r o\ rn \o \o c! \O 6l o\o .or I r o\ @corn\ocanii @o\ a !o .i <'!!rO cgo, !0) o O'6OO\O N6 oo.o F(! <i o O, O, O\or, or, O\ iC.)N trlOOOOO ooooodGl-1 @ ! oot) !L)tr(! ooq o.!otr o.i trl-t -o ! 0,)E ol ,$oZoD ocP/84.3 page 38 &o() E]k <O (J &c l& :' r! =ao -.^r ..EZ< =d,;(J F^ () ,-4 F ixL k::- .;F *z ._ o. ek 7 r,- F =J C kl rl]J F, cr.Pl84.3 Page 39 2.3.L Reinvasion 2.3. I. 1 General In 1975 the presence of large numbers of blackfly was first noted in certain Progranrrne zones despite the highly effective vector conErol EeaaureB supplied in then. It became evident that these flies came from breeding places outside the EreaEed zone and were therefore irunigrants. This phenomenon recurred every year in several zones of the Prograrune area (Fig. 11) and was designated by the term'rreinvasiont'. Ihe arrival of migrant blackfly starts with and sometimes even before, the first rains and continues for a good part of t,he rainy season. It had long been known that S. damnosum s.1. was capable of Eravelling over great distances - I50 km according to the PAG report (245). The penetration into Prograrme territory of blackfly from outside it therefore came as no surprise. Practically nothing rras known, on the other hand, about the periodicity and direction of these long-distance migrations or about the physiological and behavioural characteristics of the migranE flies. In face of the threat posed by reinvasion OCP, helped by consultants, made a very serious study of the phenomenon. Ttrese investigations were facilitated by the succeaa of larval control, which enabled all Iocal breeding of blackfly to be eliminated over very large tracts. Any possibility of confusion bet,ween blackflies originating from the treated zonea and migrants was thus precluded. 2.3.1.2 Invaded zones and source of reinvasions The five reinvasion zones are spaced out along the western, southern and eastern borders of the initial Prograrme area (Fig. 12). Practically all the migrant blackfly belong to the savanna species S. damnosum/ S. sirbanum (62 ,82, L59) except in Togo where S. squanosum is also involved (21, 61 , 226). The origin of the invading blackfly was sought ernpirically by successively treating all rivers to the south of the reinvaded zones where there existed, at the season concerned, productive habitats of S. damnosum/S. sirbanum. Reinvasion zone A exEends along the western border of the Programne area in Mali andinto the northern Ivory Coast in OOZs 03 and 04. ltre source of Ehe blackfly seerna Eo belocated in Guinea. Zone B essentially comprises the upper basin of the Bandama and its tributaries and extends as far as the Leraba (OOZ 04). Larviciding in the Marahou6 and subsequently the Sassandra basins produced a sharp reduction in the ntrmber of migrant blackfly in Ehat zone, so these basins were concluded to be the sources of reinvasion (162). In the region contiguous to zones A and B, the uestern rivers of rhe phase 4 atea, viz. the upper basin of the Sassandra and Marahou€, are themselves reinvaded while also constituting sources of reinvasion. The blackfly invading zone C in ooZ 02 probably came from t.he lower reaches of the Couo€ and the Bandama; when these watercourses were t.reated in Phase IV, the reinvasion stopped ( 162) . The species mainly involved in the reinvasion of zone D (in OOZ 07) is S. squamosum, which apparently does not Eravel great distances. It appears that many nigrEE6EEi! comefrom breeding places located less than 100 km south of the present southern lirnit of thl Prograrrne area in Togo. In 1983, migr ation of S. squamos um was on a far smaller scale,perhaps owing to the drought (61, 21, 226). The situation in zone E (in ooZ 06) is not. clear and is difficult to investigate, forblackfly breeding has persisted Iocally and sporadically on the Sota, the easternmoat Idatercourse in the Prograrnme area. It^had been thought that Ehe source of invasion night bethe Ouern6 basin, but in certain years it began before the breeding places t.here became-productive (21, 61). oo -f c l oc oq.- ,{Btr>)c 8'E&N ocP/84 .3 Page 40 ! o)!o(Eo>CC 'Se c'6E6 Ec99s(E E.IJO 8€(o.= --oUqr"L!=G9trPEg8(!> 'E9.ETO 'i=>- I I I € \ T U' u.l =ll.I o co Fz E 9, =ll. o U' uJ(J G,fo cn oz u,l G o.o o E z z o UJ zoN zo U' z u.l G, N It! I\ .\ llr) .= E =cL -c) .go .! L ,-fr I l.i / ! I - \ ocP 184 .3 Page 41 Identification of the habitats of origin of the migrant blackflies and the absence of productive larval habitats between the presumed points of departure and the points of arrival made it possible to est,imate the distances they cover. In the course of the studies conducted on the Black Volta and the Bougouriba, S. damnosum/S. eirbanum were collected more than 400 km, perhaps even 600 kn, from their presumed aepartur- point lt6Z). 2.3.L.3 Modes of nigration of blackfly: physioloeical staEe and behaviour of migrant females The rnigrations t.ake place during the first part of the April-May to July rainy season ntren the intertropical front shifts northwards. The direction of Eravel of the blackflies is from south-wesE to north-east, which is also the direction of the prevailing monsoon winds (62,82). Ttrese migrations are, in fact, presumed to take place at a high altitude with the help of the wind. During the dry season, when the productive habitats are on the northern side of the interEropical front, there is no migratory movement. The probable reasons are the low productivity of even permanent breeding places at that season, the absence of any prevailing wind, and the low hunidity which induces the fliee to remain cloistered in the forestgalleries. It appears probable that the blackflies start out on these long-distance voyages after taking a blood meal, and have their next meal after laying their eggs at the arrival site. This explains why practically all the biting females captured in the invasion zones are parous and a considerable percentage of them are carriers of infective Onchocerca larvae not distinguishable fron 0. volvulus (6L, 62, 82). The nigrant flies apparently congregate near t.he sites favourable for oviposition and still unknoun percentage of them rest on the vegetation close to the sites. AfEer laying they take a blood meal in the vicinity of the site. There is little redispersion of the migrant flies around the sites of oviposition. Thus in western Mali it was found that, three kilornetres from the river Baou16, the ABR and ATP values attained only 102 of their values at the riverts edge, while at a distance of 10 km rhe ATP was zero (169). In the present state of our knowledge it cannot be confirmed that, after laying and feeding, the females resume their migration, accomplishing it by stages, though such a hypothesis has been advanced and is by no means implausible (91). The taking of an energy meal of sugary juice is considered indispensable for enbarking on1ong-distancef1ights.NeverEhe1ess,inthe1aboratorysome@f1ies that had ingested only water achieved the same sinulated performances as some that had been fed sucrose (25). 2.3.L.4 Epidemiologigql qld operqqlonal impact of re The impact of reinvasion presents two aspecEs: (a) Ihere is an epiderniological aspect, due to the introduction of parasites by Ehe nigrant blackflies. This results in persistence of Eransmission in regions where there is no longer any local production of blackflies and in maintenance of foci of infection which could become sources of recontaminaEion, particularly in the concluding phases of the Prograrune. Wtrereas the human reservoir of parasites is everyvhere showing a very marked regressive trend, this tendency is far less evident and sometimes absent in the reinvaded zones(see section 3.1). These disturbing findings are mitigated by the fact that, within the reinvasion zones, only co*unities living near E.he rivers are affected as the urigrant blackfties do not redisperse far. Thus at Ehe rdesEern edge of the OCP area, in the reinvaded Madina-Diassa region of Mali, the ATP, which at the edge of the river Baoule can be as high as 1000, a value characteristic of a hyperendemic situation, falIs to below 100 to 3 km from the rratercourse; the situation there thus gives less cauge for worry (169)(see section 2.3.1). (b) Then there is an operational aspecE, which is reflected in the need to maintain costly treatment so as to prevent the reconstitution of local vector populations and stepby-step contamination within the OCP area. This aspect is particularly important, for it inplies continuation of larviciding in the reinvaded zones for a long period. ocP/84.3 Page 42 Experimental treatments rdith adulticides Eo destroy the migrant_blackflies on their arrival are to be carried out in the M6 basin, in Togo (see section 5'3)' But of course the surest meEhod of eliminating reinvasion is to destroy the blackflies a! source by treating the r.ratercourses they come from. This implies the possibility of extending operations beyond the southern and more Particularly the western boundary, where the larval habitats of the blackflies which invade the Progrartrtre area are located. 2.3.2 Blackfly resistance to insecticides Resistance is the ability, in an insect population, to Eolerate doses of insecticide which would be lethal for a normal population of the same species. It is a genetically-based ftr..,or".to. which results from selecEion of muEants, endowed with a better enzymatic or physiological equipment, under the pressure of an insecticide. During the past 30 years resistance has appeared in all groups of insects of medical interesE excepE tsetse flies (253). rt is therefore not surprising that they shourd have developed in'S. dannosum s.1. Indeed, the authors of the PAG rePort (245), aware of that eventua1ity,67-aste.ltt,atamethodforeva1uatingthesusceptibi1ityofS.damnosum1arvae to insectitia"" be developed with a view to establishing a nonitoring system to ensure early detection of resista.r"".o that all requisite measures could be Eaken to counter its effects. 2.3.2.1 Methods of detecE.ing resistance (a) Tests on larvae A test has been developed that can be performed in the field under OCP conditions, t.he methods hitherto reconrmended not being app licable to S. damnosum s.1. The larvae are placed in contact with the insecticide for three hours in preoxygenated stagnant water. The mortality reading is made directly on-Ehe completion of the exPosure tinE. Discriminative dosages have been deternined for rapidly detecting t,he presence of specimens suspected of resistance (94). A method for evaluating the suscePtibility of blackfly to Bacillus thur 1nq1ensr.s 1s being developed. (b) Test on adults Various methods are under study for determining the susceptibility of adult blackfly, which shows close correlation with that of the larvae. These methods are based either on topical applicafion of microdrops or on placing the flies in contact with surfaces (glass or p.p.r) coaiea with insecticides. They will make it possible to detect resistances in adults at-times of year when collection of larvae is difficult. It will also become possible to tesE susceptibility to certain adulticides such as the pyrethrinoids. 2.3.2.2 ResisEances in S. damnosum s.1. Resiscance to DDT in S. damnosum s.1. was observed in 1975 and 1976 in Togo, Benin, Mali It has not been detectedand the lvory Coast, ParticularlY again since then (59). 1n the cotton-growing regions. Resistance to temepho s in S. soubrense/S. sanctipauli was demonstrated in 1980 on the lower Bandama after 60 weeks of larviciding (68). It spread rapidly to the enEire area o distribution of that species under temephos treatment, mainly in the Ivory Coast, and, in untreated rivers, over into Ghana. It would seem to be on the increase since untreated populacions in Togo are displaying lower susceptibility. Nevertheless, the resist.ant poprrlations have not spread ouE from the initial area of distribution of the species to o"t"py the places left vacant by S. damnosurnL/S. sirbanurn (Fig. 12). In 1983, in the same lower Bandama region, a six- to seven-fold reduction in susceptibility to temephos was observed in Ehe savanna sPe cies S. damnosum/ S. sirbanum (200). Intensive larviciding with Bacillus thuringlensl.s, as s isted t fi;affions Ehat year, was immediately instituted Eo elirninate this resistant by the dry or'Pl84.3 Page 43 population (258). Until now only an insignificant number of females of these species have LeLn detected again in this region. With such a limited number it has not been possible to test their susceptibility to temephos. In 1981, after 43 weeksr utilization of chlorphoxim as a replacement for Eemephos, resistance to chlorphoxim appeared in the S. soubrense/S. sanctipauli populations already resistanttotemePh-os;thisresistancespofthesespeciesinthe treated zones of the Ivory Coast (see Fig. 13) (201). 2.3.2.3 Characteristics of resistance Temephos resistance is very stable: it persists and even spreads in the absence of specific selective pressure in untreated zones, which implies that it is dependent on one or more dominant genes. Resistance to chlorphoxim has proved stable on certain reaches, while on others it has regressed to the point of allowing the compound to be used again for short periods (in the 1982 and 1983 rainy seasons) I under the impact of these treatments it rose again to itsinitial leve1. Resistence to an organophosphorous insecticide generally entails cross-resistance to many compounds of that cIass. Ttris has proved true for S. soubrense/S. sanctipauli, which hasexhiLited1lpatentllcross-resistanceswitha11co''uooncept azamethiphos and dichlorvos (199). As, to start with, the strains resistant to temephos were susceptible to chlorphoxim, it was presuned thaE resistance to chlorphoxim was a different resisEance and not a cross- resistance. But there is nothing to prove that the same enzymatic mechanism is not responsible for both resistances and that this was not a case of rrlatentrr cross-resistance which became apparent only when the second insecticide rres used. Over and beyond the discussion on terminology t,he problem has a fundamentally important asPect. Some preparations such as azamethiphos do not at Ehe outset display ltpatentrr cross-resistance with temephos, but it cannot be assumed that they ere not liable to develop a cross-resistance. In the event of their being used on a large scate, Ehis resistance would then be likely Eo appear rapidly as happened with chlorphoxim. Over-optimism must be avoided about the possibilities of prolonged uEilization of organophosphorus preparations against temephos-resistant blackfly populations. 2.3.2.4 Operational implicarions of resistance 1983, which concerned the savanna species, o been confined to the "forestt' species nanifest only in the Ivory Coast and some regions uction in susceptibility has been recorded in the , must therefore be given t,o the possibility of es in S. soubrense/S. sanctipauli in southern arviciaing@ere to be At present the only way to cope with resistance to an insect.icide is to use anotherpreparation, preferably of a different class, which does not display cross-resisEence with it. This is what has been done by the OCP, which has in turn used chlorphoxim and then, when that became ineffective, Bacillus thuri ensis H-14 for controll ing blackfly populations resistant to temephos ( see sect For the time being, as long as resistance is confined to S. soubrense/s. sanctipauli and Apart frorn the alert on the Bandama in resistances to organophosphates have hithert S. soubrense/S. sanctipauli and have become of Ghana (Bui rapids and river Tano). A red same species in Togo. Serious consideration rapid spread of resistance to organophosphat Ghana, southern Togo and southern Benin if 1 undertaken there. does not spread to S. damnosum/S. sirbanum in savanna country, thejeopardized, p"rtic@r available. But extens the zones south and south-west of the present area, where S. soubredominant species, is deferred. Progra'rme is not ion of its operations to nse/S. sanctipauli are the In this connection, the Ecological Group has expressed t,he wish (274) that before ernbarking on any extension the Prograrmne should have two back-up insecticides available. ocP/84.3 Pege 44 ih. --i- EE E= a q -Eo c, =OC ' .:=o a = 2a H E :; E=E E E: ; i E: EE E. EE EaE EE:ir E* :e .aB: €s EEaEts -:;EH aE E EE Es Ff gE ,E Bf E o o c e@ e D /, -tI v- o/\ + x uJ G =oo =fo oz E o E D =cl, ul z U) UJ() z U' U' LlJ E, gT IF cl' Ilt t. n t I.t I{ 't 1 L I I I I) I I l. I r. 0 .t \- o i ,-rf \ I ocP I 84.3 Page 45 Consideration could perhaps be given to making do with a single replacement insecticide provided it does not belong to a group 1iable Eo develop cross-reeistance with organophosphates . Ihere exiets such a replacement insecticide, namely Bacillus thuringiensis H-14(g.t.H.t+),butformu1aEionsmoreoPerationa1thanthoseffi1dneedtobe developed. Other preparations are undergoing trials, not.ably the pyrethrinoids (see section 5.3). Of course, if resistance spread to the savanna species of the S. damnosum complex, extensive use would heve to be made, as an emergency measure, insecticides such as the organochlorines and pyrethrinoids. of B.t. H-14 and possibly other Ttre risks of resistance will have to be given major consideration in the devolution Process. A permanent monitoring system for early detection of resistance rnust be naintained and tactics for replacement or subst.itution meticulously planned. Various methods have been advocated for retarding the onset of resistance, for example mixtures or rotation of insecticides. While the former proposal is open to strong objections, the latEer, Ehough not yet backed by any results in the field, might be considered provided that at least trro preparations are available to use alternately. 2.4 Monitorins of the aquat.ic environment 2.4.L Historical ba otocols and methods The participating States, as also the contributors, had reason Eo fear that 20 yearst repeated applications of insecticides in the watercourses would cause serious disturbances of the freshwater ecosysEems. The Prograrrne therefore arranged to establish an independent advisory body, the Ecological Group, one of whose specific functions was to make sure that vector control did not endanger the environment. To evaluate Ehe impact of larviciding on the aquaEic fauna and flora, the Programe set uP a network for monitoring the aquatic environment. The task of initiating the monitoring operations, which included the preparation of protocols and the selection of sampling methods' was entrusted to the InsE,itute of Aquatic Biology in Accra and to a Eeam of hydrobiologists frou ORSTOM stationed at Bouak6. This t.ean left the Prograrme area as soon as national teams were able to take over from it, in 1980. At present all the work of monitoring the aquatic environment is handled by the participating States, but with financial suPPort from the OCP. It is, in fact, the first instance of devolution of an activicy to the States. The protocol at present applied provides for quarEerly specimen collections at selected eites for monicoring the invertebrate fauna and half-yearly collections for fish. But interventions not specified in the protocol are envisaged should abnormal nortality amongfish or invertebrates give reason to fear an "ecological disaster,, (275). Tte teams inform the Programne Director of their activities and report on them Eo the Ecological Group. Collection of invertebrates is done with the Surber sampling device, with arEificial substrates and with drift nets. Fish catches are made with trap nets and drift nets. Details of nethods, periods and times of day of sampling and number of specimens to be collected are set out in the protocol (34, L77, L79,181, 184). Thirteen study sites were chosen, nine for sampling invertebraEes and fish, one for fish only and three for invertebrates only. It is stipulated that the data collected in the field should be analysed by an independent unit every two or three years. ocPl84.3 Page 46 2.4.2 Impact of larviciding on the aquatic fauna A clear distinction must be drawn between the acEion of new insecticides on the non-target fauna, which will be dealt with below (see section 5.3), and the impact of thepiog..;"ts large-scale larviciding operations on the aquatic environment, which is the subject of this chapter. Before any evaluat.ion of the effect of insecEicides was undertaken, basic information had to be collected on the composition of the freshwater fauna in Ehe OCP area so aB to identify the most represenEative taxons which would serve as markers. Illustrated manuals on the fauna rrere prepared and ere norr in use for monitoring. In addition, a large body of infornation on the dynamics of the various species, indispensable for interpreting the changes observed after larviciding, has been collected. These studies have made 1 major contribution to knowledge of rivei ecosystems in West Africa (49,72, 150, 180, 182, 185, 206, }LO, 218, 228). The short-term effects manifested after the passage of the insecticide lrave must be distinguished from the long-term changes in Ehe ecosystem observable after several years of treatment. 2.4.2.1 Short-term effects After the first application of Abate, the drift of invertebrates can increase by a facgor of 80 during the two hours following its release, and then returns to normal after 24 hours. Some 20 to 2571 of the organisms present may become detached and drift. A11 grouPs of invertebrates excepE for the rDacrocrustaceans (prawns) are affected but the EphemeroPtera are the most susceptible. Fish are little or not at all affected. After several weeks of larviciding, the effects of each application lessen and only 102 of the organisms present drift. This is due t.o the elinination of the most susceptible groups wiitr ttre first applications (33,34,47, L78). Chlorphoxim, vhich showed much greater toxicity than Abate in t.he exPerimental trials, proved to be far betEer tolerated when it was applied regularly in waEercourses previously treated with temephos for several years (178, 208, 229)- Teknar produces only a very small increase in drift and has practically no effect on the aquatic fauna other than blackflies. 2.4.2.2 Medium- and long-term effects (a) Effect on invertebrates The situation after the initial temephos treatments is characterized by a very marked fall in the density of invertebraEes, especially if they are made in the dry season. This modification of thL fauna lasts for about a year and is then followed by repopulation from refuge zones, particularly during the rainy season, so a new balance is established. The differenE taxons are not affected in the same way. In general, however, most of those present before the start of operations are still to be found, though one or two sPecies may be eliminated from large areas. Some groups diminish considerably in numbers while others increasel the latter is true of the chironomids, probably owing to the imPact on their predators. Broadly, the impact of temephos on invertebrates, after eight years of weekly applications, has been a 302 reduction in Eheir biomass. In the new balance that has come aLout in the EreaEed rivers Ehere persists a wide variety of organisms, conveying an impression of ecological good health altogether different from the picture to be observed in those rivers in temperate countries that are subjected Eo organic or industrial pollution. Chlorphoxim has not been in use for long enough Eo evaluate its long-term impact. , ocP/84.3 Pege 47 t (b) Effects on fish The dynamics of fish populatione doeg not operate on the same time scale as that of invertebrates and its study muet be continued for many years to yield meaningful reeults. A good illuetraEion of the difficulty of interpreting fish dynamics is the case of the species Schilbe mystus in the upper L6raba basin (85). After Ehe conrmencement of blackfly control operations in 1975 thie species declined and by 1978 it had disappeared. Ttris was thought to be the result of the temephos applicatione. In 1979, horilever, without there having been any change in the Programne activities, it. reappeared in abundance. A sinilar phenomenon occurred with Alestes varenoze on the Bandama (100). In boEh casea it wae notedthat the populations returned to cheir starting level when hydrological conditions became normal again after a period of disturbences due to drought. The oCP operations have been conducted during a period of severe drought which has reduced fish catches in many river basine that were not treated. In general, catches are of the same order as in untreated rivers such as the Cavally, the Nipore, Ehe Gambia, the Niger as in other rratercourses in the OCP area (85 , 207). In view of Ehe risks of confusing the effects of hydrological changes with those of larviciding, it ie esaential that the ichthyological studies and monitoring be continued. Nevertheless, it appears certein that, at leaet in the medium term, temephos has had no detrimental effect on fish (85). ocP/84.3 Page 48 CHAPTER III REDUCTION OF PARASITE LOAD AND OF PATHOLOGICAL MANIFESTATIONS AFTER EIGHT YEARS OF VECTOR CONTROL RELATIONSHIPS BETWEEN TRANSMISSION AND SEVERITY OF THE DISEASE The objectives of OCP are, firstly, the disappearance of the disease and of its ocular manifestations and, secondly, the social and economic development of the regions protected from onchocerciasis. In this chapter it is proposed to analyse the results achieved in the nedical sphere. lhen the results of entomological evaluation will be correlated with then to give an overall picture of present knowledge about Che relationships between transmission and severity of the di""r"". Information on Ehis latter subject has very great import.ance for the lonfterm strategy. It is a basis for determining the epidemiological thresholds for settlement of the protected regions and for programrning vector control oPerations. 3.1 Medical evaluation , This is a dynamic process based on longitudinal sEudy of population samples. It includes . p"..rigological evaluation Eo keep track of the regression of Ehe various forms the parasite in ,.n "rrd an ophthalmological evaluation to deternine the effecEs of Ehat regression on the ocular manifestations of the disease. In view of the diversity of conditions in the Programme area' the results have been evaluated within the framework of its operational zones (oOZs) (see section 2.2) which precisely reflect the varieEy of situations. 3. 1. 1 Paras it.ologic aI surveillance 3.1.1.1 MethodologY of (a) Determination of the sanPle The epidemiological unit adopted was the village. In the choice of villages preference was given io those iith "borrt 300 inhabitants, a size acceptable to statisticians' survey ".itEi" and parasitologists alike. But smaller hamlets have also been included in the surveys, pariicularly in sparsely populaged hyperendemic regions. Out of t;1.e 474 villages examined betrreen 1975 and 1983, 201 had repeated visits and 161 have been selected for ghe Present Parasitological evaluation (222) ' The villages were chosen to give a representative sample of all onchocerciasis foci known at the time. They are preferentially located near the catching points of the entorotogical neEwork in order to correlatl ttre medical observations with the intensity of Eransmission. Eighty per cent. of them are in hyperendemic areas. Localities whose populaCions Irere stable, i... littIe Prone to Bajor variationsr.were chosen. rn each one care was Eaken not to mix populations with different epidemiological tioiif.", for example farm workers and civil servints. When necessary, these various iractions were put into separate epidemiological ttclusterstt. (b) Longitudinal surveillance This is based on surveys, repeaEed every three years or so' in the course of which the wtrole population of the village is examined, which means conducting a thorough census beforehand. The sample is an open one as there are exits by death and emigration and entrances by birth and imnigration' On Ehe second visit only 502 of the individuals examined the first time are traced again, buE five years later the percentage has not fallen below 40' Thus no analytical bias iE i.rl.oa,rced and the results of the longitudinal monitoring conducted by the Prograntrne are considered etatistically acceptable' ocP 184.3 page 49 (c) Parasitological examinations The basis for the evaluation is a count of the microfilariae that have emerged afEer 30 minutesr incubation of two skin snips in distilled waEer. Negative skin snips are re-examined after 24 hoursr incubation in saline solution (93, 117, 240). A count is also made of palpable nodules. In some localities these nodules have then been excised with a view to examining the physiological state of the worms afEer digestion of the fibrous tissues by collagenase. The aim of this investigation is to determine Ehe number of worms per nodule together with the percentage of sexually acEive females in order to estimaEe Ehe active life span of female rrorms (see section 5.4) (142). 3.1.1.2 The parasiEological situation in the OCP area after eight years of vector control The results of the OCP activities are highlighted by the reduction in the incidence of new infections, the diminution in the number of individuals carrying parasites, and the fal1 in the mean parasite load in the co*unities. (a) Reduction in incidence Incidence is the percentage of new cases per year. It should be zero if transmission has been interrupted. Some new cases may, however, result from infections contracted before the comrencement of control operations and producing no rnanifestations until taEer (up Eo 34 monEhs) (110). Account must be Eaken of in utero Eransmission in babies under six monEhs old (113), cases of contamination from outsiESJects erroneously declared negative in previous examinations and, lastly, errors in identification of individuals. Before operaEions began the incidence was very high in most of che OCP localities, with as many as 6O% of new cases per year in sout,hern Benin, but dat.a were relatively scanty. In face of the difficulties in deEermining the incidence among adulEs, this parameter has been studied in children born since the cornmencement of operations. They constitute the epidemiologically most sensitive group, within which the presence of infecEion constitutes formal proof of the existence of transmission. But they are in general less exposed to infection than adults. Among the 6000 children, distributed over Ehe entire Prograrune area, who were examined only a single positive case rdas found in the central par( (OOZ 01). The other cases were detected in the reinvasion zones where Ehe entomological results were not saEisfactory. Specifically, there were three cases on the western border, in Mali (OOZ 03), three cases in Ivory Coast (OOZ 04), and 12 cases on the south-eastern fringe of the Prograrrne area in Togo @oz 07) (06). If transmission had continued at the same level as before operations started, more than 200 children in the sample would have been carrying parasiEes. In conclusion, throughout the initial OCP area transmission has been reduced to a level such thaE only sporadic cases have been able to occur. The effects of the reinvasion phenomenon have been less than was feared and are limited to Ehe riverside villages owing Lo the low redispersion potential of inunigrant blackfly. (b) Trend of prevalence The prevalence is the percentage of carriers of microfilariae in a sample. It is a composi.te indicator which depends on the incidence, on cures among patients, and on population t,rrnover, with older patients dying and young disease-free individuals appearing. It indicates, at a given point in time, the exEent of parasiric infection within the popu lat ion. The reduction in prevalence recorded since the st.art of operations varies from one OOZ to anorher (Table 5). ocP / 84.3 Page 50 TABLE 5. REDUCTION IN PREVALENCE IN THE PROGRAMME AREA Year of first treatment ooz Number Reduction in prevalence 1975 ar,d L976 L97 5 L97 7 L977 L977 t97 7 01, 02, 08 04 (north-east) 01 Niger 03 06 o7 25-307" 20% r27" L07" 57" 9Z Ihere has thus been a definite fall in prevalence over the entire programme area even where there has been reinvasion or treatment failures (OOZs 03, 06 and 07). Since the mean duration of fertile life in the worms is of the order of 10 to 12 years, the decline in prevalence is slow even in the absence of new infections. In hyperendemic zones, each adult individual harbours a hoxoogeneous population of rrorms of all ages, including therefore young worns; so he will become negative only after the last female worm has ceased to emit rnicrofilariae, i.e-. at the end of a period equal to the duration of fertility in Onchocerca volvulus. At that Eine , however, a sharp fall in prevalence can be expected throughout the treated area. In hypo- or meso-endemic zones there exist varying proportions of individuals housing only aged worms; these will becone negative quite quickly. The fal1 in prevalence will become apparent more rapidly than in the zones previously considered and it will be gradual. It is, incidentally, more marked in women, who are less heavily infected, than in men. These hypotheses have been confirmed by the overall results of OCP. The cure rate with the passage of years is inversely proportional to the risks of infection before the comrnencement of operations. (c) Trend of mean microfilarial loads of comnunities The microfilarial load of an individual (number of microfilariae in the two skin snips) reflects Ehe intensity of his infection. It diminishes wtren the number of adult filariae decreases in an individual, even if some worms are still present. The mean rnicrofilarial load of a comunity is obtained by adding together the microfilarial loads of all the individuals in a sample of adults and dividing then by the number of individuals in the sample, including those who are not, or no longer, carriers of microfilariae ( 138) . As an indicator of the trend of the parasitic infection, the mean microfilarial load of a conrnunity is far more sensitive than the prevalence. In one hyperendemic village in Burkina Faso, which has been under control for eight years, it has declined by over two-thirds whereas the prevalence has decreased by onl-y 257". The divergency between the rates of reduction in prevalence and in mean parasite load is of course less marked in hypo- or meso-endemic zones. All the regression curves of communitiesr mean nicrofilarial loads plotted in the Prograrune area tend tohrards a zero point which would fall about 1I years after the commencement of vector control (Fig. 14). , ocP I 84 .3 Page 51 This trend suggests that if Ehe standard of the Prograrutre's operations is maintained for another five years, onchocerciasis will be virtually extinct in the greater part of the initial Programme area (138). Nevertheless, in some regions the situation is not developing according to this general pattern and the reduction in the parasite load is minimal or nil (e.g. Bandama, Fig. 14). These include Ehe zones subject to reinvasion - the western fringe of the Prograrrne area in Mali (ooz 03) and the Korhogo region of the Ivory Coast (ooz 04) - or faced in addition with treatment difficulties - the Kara region in Togo (OOZ 07) and the junction of the Kulpawn and rhe whiEe Volta in Ghana (ooz 08) (Fig. 15). Ihis last-nenrioned focus of Eransmission had Elone unnoEiced in t.he entomological monitoring owing to difficulties of access for the capture teams. Data are stil1 lacking for the Sota basin in Benin (OOZ 06), where the entomological results are not satisfactory. (d) Morcality of parasites Comparative studies (see 5.4) conducted in zones under control and untreated zones show thaE Ehe proportion of inactive (dead or infertile) female worms increases with the duration of the period of protection. It is between 10 and 207" in untreated areas and 7O% in regions that have been under vector cont.rol for eight years. In the latter zones the percentage of degenerated embryos increases, probably owing to the aging and lowered fertility of the wormpopulations. The mean number of female worms per nodule is less than 502 in villages that have had seven years' larviciding compared to control localities. This is due to the deat.h and subsequent disintegration of the worms. According to the prel-iminary findings, the mean duration of sexually active life in O. volvulus females is in the region of regressron curves o f mean microfilarial 3.t.2 hthalmo ical monitorin 3.L.2.1 Methodology The Prograntrnets ophthalmological monitoring has been based on: - cross-sectional surveys prior Eo operations and then seven to eight years after they are launched to determine their impacE on the global ocular status of thepopulations; such surveys have been conducted in 20 villages distributed over the enEire OCP area; - a longitudinal follorrup of a cohort of 9I3 subjects who had or did not have ocular onchocerciasis before the commencement of operations to detect the onset of eyeIesions or observe the course of those already existing; the study has been tonductedin rwo villages located in the central OCP zone and the results compared with those obEained in a population not under conErol. The object of the examinaEions has been detection of punctate keratitis, search for and counting of ocular parasites, identificaEion of irreversible onchocercal lesions (sclerosingkeratitis, iridocyclitis, optic atrophy and choroidoretinitis), and determination of overallblindness rates (270). rn addition, in all the surveys visual acuiEy and, in certain cases, reduction of visual field have been evaluated (153). 3.1.2.2 Course of ocular disorders in onchocerciasis tients liv in zones that have been u er contro for more than ve years (28, 29, 7 The results of Ehe fol lowing: 1982 and 1983 surveys in the twenty selected villages show the (a) subjects free from ocular onchocerciasis before the starL negaEive in 962 of. cases. 10-12 years, an estimate borne out by the trends of loads of conmunities (77). of operations r^rere still ))I t- (/ I ocP /84.3 Page 52 FlG. 14 TREND OF MEAN MICROFILARIAL LOAD OF COMMUNITIES IN THE DIFFERENT ZONES OF THE PROGBAMME FtG. 15 TRENDS IN PARASITE INFECTION LOAD AMONG ADULTS OF DIFFERENT COMMUNITIES 50 c I ) I a l_\ I I , - lnitial OCP limits (2 lntensitv decreasing rapidly(p Decrease in intensity still insufficient ! No change Numbers corresponding to graph o4o oO6 -oCP EEgo cE .-o oQ !ot E.s 2otgP3; = t0 I 0l 234s6 7E9 t 3 -EINDIATTA4 '-\ \- IEFTEI- ' '...........:.. KOULPEOLGd REO VOLTAN TOGO -*--t*-BANIFING IV .t-.rrri. - 0 2 Years since larviciding began ocP/84.3 Page 53 (b) (c) (d) Subjects affected by punctate keratitis had progressed Eowards disappearance of the sign in 90% of. cases and no cases of aggravation were found. Carriers of low microfilarial loads were cured i.n 702 of cases, the condiEion was unchanged in 167., and it had worsened in only 132. Carriers with heavy loads showed diminution of their loads in 682 of cases. It 382 some worsening was noted, but not such as to threaten eventual blindness unless transmiss ion recontrnenced. (e) Thirty per cent. of early, stage I eye lesions were cured, lO7" were improved, 307. were stabili:-zed, 252 had worsened and. 5% of the patients had become blind. (f) Seven per cenE. of advanced, stage II lesions had progressed towards blindness. Global blindness rates had in general declined owing Eo the eliminat.ion by death ofblind persons, whose life expecEancy is shortened (120), and the lower incidence of new cases. rhe incidence of blindness was zero up to 30 years of age (29,176). The longiEudinal study conducted on two separate cohorts in the village of Mouvielo inBurkina Faso for nine years before larviciding began, from 1966 to 1975, and then for eight years after it had started, from 1975 to 1983, is particularly illustrative (fig. 16). Thefirst cohort consisted of 82 subjects and the second of 75, all age groups in both sexesbeing represented. Whereas during the nine years prior to larviciding eye disorders had increased by about 502, during the second period the number of patients with punctate keratitis diminished by 5O7" and the number with very severe lesions by 207", while the number of blind parienrs fell from 10.4 ro 1.3% (136, 176). 3.L.2.3 Relations between vector control and ophthalrnol osical findines t,he inprovement in This applies to the The vector control conducted under the Prograrune has considerably reduced the risk of eye lesions appearing. What is more, it has everywhere made possible spontaneous improvement of the ocular status of subjecEs already affected. Only some of the patients with aivanced, sPontaleously developing lesions or very high rnicrofilarial loads showed a worsening of their state ( 176) . where the entomological resurts have not been fully satisfactory ocular status, though less marked, is nevertheless very appreciable. zones subject Eo reinvasion. 3.1.3 Case of the Farako basin The hyperendemic focus on the Farako, in the Sikasso region of south-eastern Mali, hadbeen effectively under conErol by larviciding with DDI since 1966. However, the size of the zone treated was not sufficient to obviate reinvasions and the ATP stood at 100 to 150 until1975, when the focus was included in the Prograume and treated with Abate by helicopter.Since fhen the ATP has always been below 50. The results of 17 years of vector control, the last eight of them under excellent conditions, in Ehe Farako basin are valuable as an example for establishing a projection ofthe trend of onchocerciasis in the greater part of the irograntrne area over the "oii.rg years.Hencerrthe Farako casett has been accorded very particular attention (109). Detailed analysis of the results in four villages shows that between 1971 and 1975, wtrenthe focus was treated in isolaEion, incidence was from 3 to 102. The percenEage became verylow when the focus was integrated into the Prograrmne's Ereatment zone (fable 6). prevalencefell to about 1%, whereas it had been about 502 in 1966. out of 554 subjects examined in ocEober 1983, only five, aged over 30, were carrying microfilariae, which means thatpractically all the infected individuals were cuiea. onchocerciasis has t,herefore been unable Eo persist and.has been progressively reduced to a few sporadic cases. As of l9g3 ithas been virtually elininated from Ehe Farako focus. ocular paiasitization has alsodisappeared and by _1976.only a single person carrying an ocular microfilaria was detected(compared co L27" of subjects in f968) itSS). Of course, some elderly subjects haveirreversible lesions, but without any parasites being present. ocP/84.3 Page 54 6oo -ct o =.9 a €^ E3 9P coICD e c,:tE= oo G .= .E' co F Goo4! o E o '= 3co -ooOCD OFCr 'aP =o, c,o o .E E c e FrG. 16 TREND OF OCULAR ONCHOCERCIASIS IN THE VILLAGE OF MOUVIELO BEFORE AND AFTER VECTOR CONTROL \^JAS INITIATED Number of subjects with ocular onchocerciasis Subiecs with punctate keratitis Subiects with very severe lesions I ncidence of blindnes t975 r966 rq r983 I ,3'/. r":-r-n olIIIl lst examination n 2nd examination 37,7 23,4 11,3 4 I 71,3 5? 25 20 ocP I 84.3 Page 55 TABLE 6 INCIDENCE OF ONCHOCERCIASIS IN FOUR VILLAGES OF THE FARAKO FOCUS BETLIEEN 1971 AND 1983 o.81[(1 out of 119) 0(out of 75) 0.6 ( 1 out of t72) L.67!(1 out of 63) It must be stressed that the very frequent migratory exchanges with the Ivory Coast have not resulted in the maintenance of a parasite reservoir. This is an observation of great interest for the future planning of Ehe long-term strategy. It would therefore be invaluable to study the nigratory movements of the Farako population with the help of a geographer. Final1y, from a general viewpoint, the study of the Farako focus confirms the difficulty of eliminating transmission in a smal1 focus subject to recontamination, whereas the incidence became zero as soon as the focus was incorporated within the OCP operations. This example must be taken into account by any countries contemplating the implementation of onchocerciasis control prograrrnes in limited, non-isolated areas. 3.1.4 Conclusions regardins the endemic onchoc erciasis situation in 1983 in the Programe area The overall results of the epidemiological evaluation of the Prograrrne after six to eight years of antiblackfly treatments add up Eo an incontrovertible success. Ninety per cent. of the initial OCP area appears fulIy under control. The exceptions are the reinvasion zones, where only a small number of riverside villages are concerned, and the zones where larviciding has fallen foul of technical difficulties. It has not yet been possible to evaluate the epidemiological consequences of resistance and in any case they only concern the southern fringes of the initial OCP area. Emphasis must therefore be laid on the need to cope with reinvasion in the long-term strategy. Ihis implies either treatmenE with no limitation of time, and using techniques still under study, of Ehe reinvaded siEes, or extension of operations to the sources of the re invas ions . The failures of Ereatment have had direct repercussions on the epidemiological results. Ihe standard of larviciding operations will Eherefore have to be maintained, in Ehe future strategy, at a very high leve1, at least until E.he parasite has disappeared from the areas concerned. In the area considered as well under effective control, a single child born since the comencement of operations has contracted onchocerciasis out of 6000 examined. The mean microfilarial load of the cornmunit.ies has decreased rapidly and after eight years of campaigning it stands at only one-third of its initial level. Analysis of the curves of reduction suggests that rhey might be nearing zero point 11 years after E.he starE of operations. Vi 1 lage Between 1971 and 1976 Total incidence Between 1976 and 1983 Tota1 incidence Kafela Mamabougou Folasso Ma 5.87.(10 out of 173) 3.07.(3 out of 99) N.A. 1o.77.(6 out of 56) ocP 184.3 Page 56 It is then that we should see a sharp fall in the prevalencer which hitherto has diminished o,.ly by 25y". The preliminary study on adult worms extracted from nodules puEs the mean duration of their reproductive life at 11 or L2 years' The risks of ocular lesions appearing have become minimal and many subjects exhibit spontaneous improvemenE of their eye disorders' If the programne effort is maintained with Ehe same effectiveness, it can be esEimated that the situation becween 1986 and 1990 will be comparable to that on the Farako ia 9O% of the programe area. Onchocerciasis will no longer be in evidence excePt in the form of sporadic imported cases or, of course, irreversible ocular sequelae. 2 Relations beEween Eransmiss ion and cli nical manifestations of onchocerciasis3 3 2.1 Duality of savanna and forest onchocerciases It was in Cameroon, early in the 1960s, that rnajor differences were first observed between the clinical manifestations of onchocerciasis in savanna "tU 1ot"5g (44). In theformer of these environments the disease is serious and produces ocular involvement leading to blindness rates of up co LOZ in certain hyperendemic villages. In forest country, at an equivalent level of endemicity, onchocerciasis is much more benign: eye damage is less frequent and blindness very rare or non-existent' Whereas in Cameroon forest and savanna areas are seParated by the Adamaoua mounlains, to the west of that country the two tyPe s of vegetation interpenetrate and overlap over a wide rransitional belt (111, 118, 119). The savanna vectors S. dawrosum s.s./S. sirbanum drive wedges into the forest block, along the the lower Bandama. The ttforesttt species great rivers, .Iio-ffifttg the Gulf of Guinea on S. soubrense/S. sancti au1 i also colonize the hunid savanna rivers uP to the 10th parallel a are om .nant sPec es in the savanna of the souEhern parts of Benin, Togo and Ghana. Thus in a large part of their area of distribution they cohab it with Ehe savanna species (Fig. 6). S. squamosum is also found in both types of country and only S. yahense seems fairly strictly tied to the forest. Depending on the severity of the disease and the distribution of the vectors (111), three epidemiological tyPes can be distinguished: - severe savanna onchocerciasis north of the ninth parallel where the dominant or even the sole vectors in manY areas were S. damnosum s.s./ 'S. sirbanum; - forest onchocerciasis, hitherto considered benign, and limited to the regions from wh ich S. damnosum s.s./S. sirbanum are absent; - a transitional zone where the clinical picture of the disease varies in severity according to site and where forest and savanna vectors cohabit. For nearly 20 years an explanation has been sought for the difference in pathogenicity of the disease. The dismembermenE of the S. damnosum s.l. complex into a multiplicity of forms has shown that the forest and savanna vectors belonged t,o d ifferent species whose intrinsic vectorial capabilities are not identical (45, LO2,123,126, 157). But the engomological factors hitherto taken into account do not fuIly explain the geographical heterogeneity of the clinical manifestations. Itre possible duality or even plurality of the parasite has also been considered. Savanna microfilariae cause more extensive lesions in the rabbit eye than do forest ones(43,63). Twenty per cent. of forest microfilariae exhibit differences from savanna miciofiiariae in-tireir conEent of acid phosphatases (98, 106, 119,215). Microfilaria, which is frequent in the savanna, is rarely observed in the forest (105). Recently, electrophoresis of isoenzymes showed variaEions among populatiolrs-of adult worms, but the "genetit distancesrt betweln these populations were very smal1 (77). There is thus a series oi pointers to suggest that O. volvulus is a complex of two or more forms, but there is still no decisive evidenie to back-Efiffial6Ehesis. ocP I 84.3 Page 57 None of the sEudies on the parasite has concerned the infective larvae (t 3) founa in the vector. Not only is it impossible to differentiate between those deriving from savanna parasitee and those coming O. volvulus cannot be disti st parasites (if indeed such entities exist), but from the filaria of bovines O. ochengi (see from fore nguished sEatio-;-sJ). And yet it is essential Eo be able to determine wh 1Ch form (or forms) of filaria each species of vector transmits if we are to ful1y appreciate Ehe patterns of transmission in the intermediate zones. In the present stat.e of our knowledge it is noE possible to determine whether the factors that condit,ion the severity of onchocerciasis are to be sought in the parasite, the vecEor or the vector-parasite association, or are of a quite different order, irununological for example. 3.2.2 Relations betlreen transmission and clinical manifesEations in the savanna The data collected before vector control operations began showed that when the ATP was below 200 (40) there were few or no severe eye lesions, though Ehe prevalence might be as high as 602. When the ATP rose from 220 to 2000, the ocular parasite rate increased fourfold and the blindness rate could be as high as 102. With an ATP of over 1000, all the condit.ionsfor hyperendemicity were fulfilled and the very existence of comnunities was threatened (102, 139). There were no preoperational data on clinical manifestations observed in regions where the ATP ranged between 50 and 200. The working group on conditions for settlement of lands under control, which met in Geneva Lt L977 (246), reckoned that, to maintain a safety margin, an ATP of 100 and an ABR of 1000 were the tolerable linits of transmission and biting in the savanna zones of t.he Prograrune. 3.2.3 Relation between transmission and clinical manifestaEions of onchocerciasis in the West African forest Typically forest onchocerciasis is in general found only beyond the southern limit of the area of distribution of S. damnoruq s.s./S. sirbanum. Whenever these species arepresent, albeit only for par-ffiffar, inTilT6-n but that of stray populations, the clinical picture of the disease becomes more severe. The forest vectors are S. soubrqnse/S. sanctipauli, together with S. yahense; this atter species is associated, along sma1l watercourses, with a particularly benign form of onchocerciasis. It is necessary to be more reserved with regard to the s)mptoms accompanying Ehe presence of S. squamoeum , which is itself a complex of several forms (see section 5.2). As can be seen from Table 7, on the lower Como6 and the upper Cavally, in the Ivory Coast, ATPs of 5000 and over are noE associated with cases of blindness. In "foresE'r onchocerciasis regions the tolerable Limits for ATP and ABR are well above the ceiling values established in savanna country. It even appears difficult to establish any such limit values in regions where the disease is relatively well tolerated by thepopulations, at least as regards ocular damage. IE should be noted that in the Prograrrrtre area purely trforesttt onchocerciasis is found only in the rather resEricted territories of Phase IV and perhaps in the southern extension zone (oozs 05 and 09). The epidemiological observations were made in a small number of conrnunities and need Eo be confirmed on a much larger sample. Ttre epideniological evaluation team is at Present conducting extensive sEudies in forest country and in the irintermediatert zone. 3.2.4 Relation between Eransmission and clini cal manifestations in intermediate zones In the intermediate zones where forest and savanna vectors cohabit, onchocerciasis, albeit less severe than in the savanna, nonetheless constitutes a locally important pubiichealth problem since blindness can affect z co 5i( of the population. 1 ocP/84 .3 PaSe 58 ATP levels in which the savanna vectors alone appear to be implicated are sufficient to create serious situations. At Tetetou, in southern Togo, where the blindness rate is over 37, the ATP due to the S. damnosun/S. sirbanum pair is h igh enough to account on its own for in Burkina Faso where the ATP valuethis situation, judging from the analysis of situations was identical (111). The role of S. soubrense/S. sanctipauli is controversial. In t.he ideal survival conditions of the laboraEory this pair Eransmits both savanna and foresE O. volvulus (44, 102, 108, 111, 174,226). In natural conditions Ehese blackflies have been found infected in savanna zones where ochocerciasis exhibited a high degree of gravity (Massadougou in the Ivory Coast, the Bui rapids in Ghana, and Ehe lower Mono at the frontier beEween Togo and Benin) (174, 226, 232, 238). ltrough some authors think that the parasiEes concerned are of savanna type, this is difficult to prove since there is no way of assigning the infective larvae of filariae transported by blackflies to a population of forest or savanna parasites. The tolerable limits of Eransmission for setElement of lands in intermedia not been established. Transmission there is the aggregate of the ATPs due to S. damnosum s.s./S. sirbanum and to other species of the complex, in particular S. sanctipa" li. Nothing yet gives reason t.o suPPose thaE the lirnit of Eolerabi Iortrei Is different from what it is in the savanna, namely 100. For no limit o can be set for ATPs due to olher species as long as their role in the transmission of severe forms of the disease is not known. The study of the role of S. soubrense/S. sanctipauli assumes corres pondingly greaEer importance when those forms are resistant to instcticides. Their destruction necessitaEes te zones have S. soubrense/lTty-ffi- f tolerability the use, technically difficult and very cosEly, H-14. of formulations of Bacillus thuringiensis ocP/84.3 page 59 @r o\ a oo.t$Oi! .$ oE .! .ico o(!@prO o\O oo! d -'c, Q) o.! 0Jr).d tA Eoi o o!'i !'iQ.C ori cAr -oo, -..o- OoDdupoa o(!OJ|| O :,AJ(-)..!d o >>o0 o-C lr OOF OF tr H! C$ -r! .itr! iEoo -o(!0rc > tr$u 6 0-c o(4l!c, o) u, .. cuo oc) oOtr i( u) o o o0)tr u^ 'o (!d\eC liv FA O\ \.o Oi co \o O\O O\O O c,) <'d ir cr) \O oo -)@ oooo C.) \t \ti oo c,r \o @(a (\d * ca OO U)cic ooo O-oo@.r 0)(i oH!Htro1..o>(! o oJ lrf{,O!O tu.J O Ln$ @o\ ro 6@ XXO0)1r\ !!N ooizz -f, co N c') dN .f, \o OC.Chddcn @o GI oN \OJ NT (fl \O -f,N olH ! ..tO(io d(! o r.doootr O lr^o oE{H O Ov(!>O >.dEo!otrotraruo CD(n rn@ -f -t cn o\ r)o\ -$ \o xxool !!dOOnzz \o -tN -f tn c.r oFl (n (o rfi O\ .$d) \t rO\ \oO H\O O\@ -, -t O \O r'') \C) Ln diH cic7) rl^1rn tn\o o E(! (H ot|ltrrUEooQ (U oE rn o\ rtn dc{ r- rL^ \o 1r\ \o F- O\ \Or@ 6CO O\ (n O c.) (') \, Or^ caO\ r<. do^ dcTt ii r\o O\Oc! ca \OH o@ c{ i HCO .f,\O ro iNca .+ o Oo(! o.J ootr traO Oi\e d (Jv(d0 >E(uo!tr orO 60\ rrNT @o \o @ @ N NT O\ \O rN @N oi@@ r\O -) (,)\O \O ir (\r\o \o O\\O Ln.f, c.)-J 60. cO cO \O \O coN <-r NN (\.l -)NN orn co c!\Or tnN ioo x o(A hE rqEf&t f&E hE f&Er&E EEhE r&E hE r&E tr 0)(!@ o"O$F >tl <lq) _t> v(! t- oO N o, e.l -? \o N ! OO OO ooo o o c\ oo\o oO N oo c{ o b0(! .i ,o o^ .i !!o.nc$clJf!oooOl\oE.nE ool Fv OvolFI !L .i 0) x(uB .ir(!0$:! olo .r (d(Urd-o3l c, o - o 0J .x r! 3Ouo.--oqj$ -C (d- 'O o0 O J ]i0.J oi 0j O 1, o A .oF$ d3 O< o(d oE(J 0) o U) o^)!.J o! :! 0JOla F.f v (!^(J q) !(!otro$oo 5v ! q 3QQ'O(J .oooo!(d O @O o >9. A ,f! O !ooo cc(UtrOH .i 0J.i a.; fr >Ol .il O,ll ji ! o ! ! rr b0! rO O ! oataFa!>at oEa oEa (UCQ rOH O)Zv Av Av llv tl ot\ (! o (! an t U) 14 F] FA H& Fl (J H CJo F-lo H E]o H F] rd z or ts z 14 tdBH ca U)zoH H F-] 14d - trl Fl Eq F ocP/84.3 Page 60 CHAPTER IV IMPACT OF OCP ON SOCIOECONOMIC AND HEALTH DEVELOPMENT 4.L The different aspects of socioeconomic and health development The final objective of the Prograrrne as defined in the PAG project (245) wasttto reduce the impact of the disease of onchocerciasis Eo a level where it no longer rePresents either a public health problem, or an obsEacle to socioeconomic developmenE, nor a bar to the reclamation of good arable land at PresenE vacantt'. Activities began with vector control operations whose resulEs lrere very soon perceptible. The epidemiological impact of that action took longer to become aPParent and o.,ty.,o, has it becl*e possi6le to dtternine its initial results and general trends (see Chapter III). Ttre socioeconomic effects are stil1 slower to emerge and meaningful analyses can be conducted only in the regions where t.here has been control for a long time. It is in years to come that we shall be able with advantage to extend such analyses to the entire area covered by OCP. Ihe term ttsocioeconomic and health impact" is not very precise. It brackets together a large number of economic, social, cultural and medical phenomena. It is therefore important to state precisely what it covers; - settlemenE and resettlement of the valleys, organizat.ion of space and resulting cultural, social and economic changes; - enhancemenE of working capacity by diminution of the clinical manifestations of onchocerciasis, in particular blindnessl - improvement of the living environment; - improvemen! of the general standard of health and develoPment of health infras truc ture s ; - parEicipation of comnunities in the Prograrune. First of all, however, it is necessary to recapitulate what is known about the relationships between human ecology and onchocerciasis, a subject Ehat has been studied in depth in the OCP area. 4.2 Onchocerciasis and human ecology The epidemiological studies conducted in this region showed that individuals and corununities living under the same apparent conditions of transmission exhibited different clinical manifestations according to the location of Ehe village, its size, the density of the population and the pattern of housing, agricultural practices and professional activities. 4.2.1 Location of villages Before the Prograrmne began it had been noted in Burkina Faso that the level of endemicity in a village depended on the proximity of the blackfly breeding site. But two cormnrrnitiLs locaEed at an equal distance from the breeding sites could display very differenLt levels of endemicity according Eo whether they were in Ehe I'front linet' or whether other settlements came between, attenuaE,ing E,he risks of transmission. In short, severity starts to decrease from Ehe front line of settlement, whatever its distance in relation to the river (227). In Ghana (71) and Mali (84) it had been observed that corununities moved away from the rivers when onchocerciasis became intensified and Ehen moved back towards them when the situation seemed to them less serious. I ocP 184.3 Page 61 4.2.2 Size of villages It was noted in Ghana, and then in Burkina Faso, that blindness raEes of over 52 were in general found in villages of 200 inhabitants or fewer, whereas they were exceptional in settlements with 500 or more inhabitants. Furthermore, there uras no population growth in the connnunities where Ehe blindness rate equalled or exceeded 57" O0, 114, 196). There is interaction between two phenomena: the risks of blindness reduce Ehe population through departure of young members and premature death of blind persons. Hence those who remain are subjected to an increased rate of infection, since the number of bitingblackflies in the area of a village remained relatively constant. Conversely, there appears Eo be a critical mass above which transmission of the parasite is diluted among a larger number of individuals and no longer possesses sufficient intensity to cause a high rate of blindness, which is proportional to the number of accumulated infections. 4.2.3 Land occupanc y density An analysis conducted in Burkina Faso showed that one of the factors governing the severity of onchocerciasis was the population density in the part of the village land area effectively utilized. Generally speaking, when the population density there is above 50inhabitants per kmz, the blindness rate remains below 57" even in front-line villages in hyperendemic zones; their demographic pattern is identical to that of uneffected courmunities. Contrariwise, in settlements exposed Eo an equal risk but, where the populationdensity is below 35 inhabitants per kmz, the blindness rate exeeds 52, the social iaLricdisintegrates and population growth falls below l"l OO, LL4). SponEaneous or organized migrat,ions into the Burkina Faso valleys under control result in an effect.ive population density generally below 35 inhabitants pei km2 (see section 4.3). The nigrants practise extensive farming wtrich is facilitated by t.he development of individual means of transport. 4.2.4 Pattern of habirat It was also demonsErated in Burkina Faso that. the blindness rate varied very noticeably among ethnic groups (e.g._Lobi, Dagara, Birifor) living side by side but having different space occupation systems (115, 216). Each settlement contains two areas of economic activity: (a) the peridomest.ic area, which comprises residential space, permanent fields and water Points. The degradation of the planE cover and the elimination of the gallery forestfor the laying out of cultivated plots, often contiguous, militate against ttre aisplrsion ofthe vectors. In addition, the concentration of the population into a limited "p."" reducesindividual contact with the vector; last1y, villages induce an t'avoidance phenomenon,, on Eheblackflies. (b) the external agriculEural area, which comprises the more distant temporary fields, Ehe land left fallow, the ground traversed in stock herding and wood collection, etc.; mainEenance of the plant cover is conducive Eo circulation of the vector and its conract with man is very inEensive in isolated parcels. The movements and distribution of the populations bet.ween the two spaces condition the severity of onchocerciasis. rn the region of the Bougouriba in Burkina Faso the Lobi have a very dispersed habitat which eliminates the phenomenon of avoidance of the vi1lages. They practise extensivefarming in the external area and their blindness rate is over 57.. -rire Birifor and the Dagariare grouPed in compact-villages on hillsides or in the areas between Ehe rivers; theypractise intensive agriculture in the peridomestic area and work communally, which."irr"." the time,they spend in the fields; the low ground has been parcelled out into rice paddies,eliminating the plant cover and the galleries; in thos" "orrditions, Ehe blindness rates arefar lower than among the Lobi. These conrnunities have developed . irrr" social mechanism forresistance to onchocerciasis. ocP/84 .3 Page 62 4.2.5 Professional activities Because their work is done near Ehe rivers, some professions are particularly exposed to rhe risk of onchocerciasis: fishermen, rice gro\rers and ferrymen, for example. Hard and fast conclusions and generalizat.ions must., however, be avoided: rice growing, for example, is a high-risk activity in Sierra Leone (167) and the Ivory Coast (Senoufo region), where it is practised in the vicinity of the permanent rivers, whereas in the Dagara region of Burkina Faso it contributes, on the contrary, to reducing the dispersion of blackfly through destruction of rhe plant cover (115), and hence to limiting the dissemination of the parasites. Ihe risk inherent in each activity musE therefore be evaluated in the local ecological and social conEext. Women are in general less heavily infected Ehan men owing to the repartition of labour. Ihis is borne out in Burkina Faso among the Lobi and Birifor, where the women farm only the peridomestic area while the men Eake charge of the external area. Among the Dagari, on the other hand, where they share in the same tasks as the men, they exhibit the same rates of infection as the latter (115). Among the Senoufo in the Ivory Coast, where only the women practise rice growing, they are more infected than the men, as the surveys conducted by OCP have shown. The development of farming with draught animals or of mechanization reduces working time in the fields and hence contact time nith the vector; it thus reduces Ehe risks of severe onchocerc ias is . 4.2.6 Impact of research int o human ecologv on onchocerciasis control activities and s trat egv Research into human ecology has brought to light a whole range of social determinants of onchocerciasis endemicity. This information suggests possibilities of organizing space from an epidemiological viewplint, buE it is noE certain that, economically and/or socially, a pattern of development answering the requirements of onchocerciasis prevention is possible' ResetElement of the valleys by comnunities with high population densities (over 50 inhabitanEs to the km2) might, for example, be a preventive measure against Ehe return of onchocerciasis even aft.er Ehe cessation of blackfly control. 4. 3 Reclamation of valleYs The economic development of the zones under onchocerciasis conErol does not depend on OCp, but on the States, which can request external suPPort, either international or bilateral. OCP can therefore only tike note of the new situations without having been able to intervene in the processes that created them. Its role is not, however, purely passive: it provides information on the entomological and epidemiological situation in Ehe zones that are to be developed. Ihe development of Ehese "new lands" takes place either within Ehe framework of planned project.s or through sPontaneous' unsuPervised migrations' 4.3.L Planned economi c development proiecEs in zones under control Each State has approached ghe development of the zones under control according to the dynami.cs of iEs olrn economy. A synopsis of completed, current or planned activities was .Lbritt.d by each of the participating States to the JPC in 1982 or 1983. Some countries have launched specific seEtlement campaigns while others have included these zones in broader projects, regional or national. In these latEer cases it is ofcen difficult to deEermi.r" ih"-"r"a of ihe zones under control within the scope of each project. BuE there is nothing surprising in this, as onchocerciasis conErol is only one of the components of the "orpf.* interactions conditioning the whole continuum of development ;;;j;;a;: Srill, it is noreworrhy Ehat the density of development projects is far higher in the areas included within the Progranrne than in other Parts of the national terriEories' The prograrune has therefore effecEively played the role of mobilizer that was assigned to it in the PAG report Q45). ocPl84.3 Page 63 The number of projects, which stood at 160 in 1975, had risen by 1982 to 320 in the OCP area as a whole, and the relevant investments had quadrupled. Some projects are i-n process of implementat.ion or even terminated, while others are in course of preparation or search forfunding. An enumeration of project, surmnarized in sections (a) to (g) Letorr, was supplied by each State to the JPC at its 1982 and 1983 sessions. Fig. 17 shows their geographicaldistribution (256, 257, 258, 269, 270, 271, 272). Most of the activities launched or contemplated relate to agricultural development and its upside and dorsnside infrastructures: means of production, road system, water resources, agricultural foodsEuff industries, and organization of the living environment. This last element comprises village housing facilities, the healEh care network, and the educational and school system. (a) Benin (256) Ihe provinces of AEacora and Borgo, totalling 72i( of the national territory, are included in the Progranrnqrs treatment zones. These two provinces are sparsely populated (10 to 15 inhabitants per kmt) and offer good reception possibilities for migrants coming from overpopulated regions. Almost all the rest of the country is included in the southern extension zone. fhe development of the zones, considered in a broad sense, under control is integrated into the national and regional planning process, and a specialized unit has been set up in the planning directorat.e. The preparation of the l0-year plan was preceded by the buildin5up of a data bank on natural resources (inventoried by remote sensing), on soilpotentials and on the socioeconomic st.atus of the rural population. The plan specifies 16 investment projects, of which two are in course of implemenEation. Representing a financial outlay of 14 billion CFA francs, they are concerned with integrated rural development, improvement of fruit and other food-crop product.ion, and stock-raising; rice growingprojects are under study. The plan assumes that the development of the zones under control is to be done by volunteers and not through authoritarian population relocations. An attractive setting must therefore be created by developing village water resources, the road network and the educational infrastructures. A very special effort is being made on the healEh side, givingpride of place to preventive medicine and the traditional cures. Ttrree pilot zones have been established at Segbana, Kdrou-Pehunco-Sinend6 and Materi-Coby. It is intended that the populaEion should be closely associated in the selection as well as the execution of the various projects. (b) Ivory coast (269) In the Ivory Coast the developmenE of the regions under onchocerciasis control is not tackled zone by zone but incorporated into national progranmes in specific spheres or integrated regional development projects. The sugar programne conducted by SODESUCR-E began in Ferk6ss6dougou and has been or will be extended to the Ferk6 II, Borotou, S6r6bou, Katiola and Zu6nou1a complexes. SODESUCRE at Present provides 12 000 jobs, not including temporary employment for the cane harvest. When conpleted, the sugar progranrne with its industrial spinoffs will provide a living for 250 000 persons. The water requirements for the sugar cane necessitate locating plantations close to the watercourses where onchocerciasis endemicity was often very severe. Hence there is a definite correlation between Ehe activities of OCP and the implementation of the sugar plan. A market garden progranrne, which st.arted with the creation of small irrigated zones(NtZi Band6ma, Rubino, and Ferk6ss6dougou) in 1974, is being developed in two large disEricEs at Marabadiassa and Sinematiali. These are farmed by over 1200 families whose annual income is of Ehe order of 400 000 CFA francs. Downside, they have given rise to a food processing industry producing canned vegetables, fruits and Eomato concentrate. The areas under crops are in valleys with high endemic onchocerciasis prevalence and are Eherefore very directly concerned by OCP activities. t ocP/84 .3 Page 64 c€t tr? oHht EstE oo E -EiEE EiE 2 ?;F 3 f;HE tr .9 -GE sbEq5 -3 xg o t'-C o! E Po u A?b g5 E t8 E9ootro 8.o o.= o9o.E =Ef o .-O C E.[ Eu,o a- clt 00 C') E lrJ UJ -F o z o U' 3t =(9 o- UJ F E oElt (n () u,l o ccG z UJ =o.o u,l uJ o I =oz oo UJ I =aD UJz oN z a = 0 tr jffiNNffiMtrI + + +!, I ./ t. /- \ .1 , .i;l'*- iilii:a? "'?-:-qr-' + + (l) @ ct) J l -oo IJJ .L() o 1t+ t I -J+ -.'i') lrrl' t1 ++ 1l t +' l t { + + + -.-.*-*h. - .-. -. -.-./'5.r:l: ++ /'^'-'-'.--.2 -'- t I l+ ocP 184 .3 Page 65 A 1000-hectare project to grow fruit (pineapples and avocados) for export has been launched in the Kan valley near Ti6bissou; vegetables are Eo be grown in combination. Rice production declined afEer the abolition in 1977 of SODERIZ and of government financial support. Ihe lvory Coast, formerly an exporter, found its rice imports increasing year by year; measures to restimulaEe rice growing are under study. Seventy per cent of the rice produced comes from the forest region and 302 from the savanna. Half fhe cultivated areas in the forest and all of those in the savanna are in endemic onchocerciasis zones. The relations between rice growing and onchocerciasis have been discussed above (see section 4.2.5). In the northern Ivory Coast, which was included in the initial OCP area, their agricultural practices put rice growers particularly at risk from blackflies and onchocerciasis. The coffee and cocoa prograrmes launched in the 1960s are the cornerstones of the Ivory Coast economy. Located in forest or pre-forest regions, they involve 375 000 fanily plantations. A11 activities in this sphere come under Ehe responsibiliEy of SAII,IACI. One third of the cocoa plantations are located in the Phase IV Prograrune area. Most of them, however, are not under direcE threat of onchocerciasis, which in any case generally takes a less severe form (see section 3.2) in the region concerned t.han in the savanna. The soya, manioc and coconut prograrroes, though located in the onchocerciasis zones of the Ivory Coast, are less direccly concerned by this endemic disease, being farther away from the severest foci. A11 these prograrrEnes are accompanied by development of the rural infrastructures: road network, village water resources, dispensaries, schools, shops, together with the provision of means of production and the creation of cooperative associations. A very considerable efforE at rural promotion, including health and nutritional education, has started. In the savanna, integrated projects have been launched by the CIDT, a society for regional development of the savanna. Finally, Eo alleviate the shortage of animal proteins, the Ivory Coast has launched, beginning in 1975, a plan for development of stock-raising in t.he savanna regions, of continental fishing in the great dam lakes, and of fish firming. Livestock ianches, like the one in the Marahou6 region, often occupy valleys that are uninhabited precisely because of onchocerciasis. onchocerciasis control has a directly observable impact on sugar growing and marketgardening, as also on rice growing. Elsewhere, it is a significant facE.or in the developmentprocesses of all the parts of the country where the disease is rife, as is shordn by the report (269) submitted by rhe Ivory Coast to rhe JpC in 1983. (c) Ghana (257) Ghana has included the developmenE of the regions under controL in its five-year plan, whose objectives are to increase production, reduce the disparity between rural and urbanincomes, and establish forward-looking infrastrucEures for lh. r..r.g.menE of land and rdater resources. Nearly a 100 000 km2 (Northern Region and Upper Region), intraUitea Uy2.5 million people, are benefiting from the oCP treatment operat.ions and a stilI larger areais comprised in Lhe southern extensions. The effort made by the Ghanaian authorities has been applied to the development ofirrigated rice, tomato and sometimes cotton growing. Over 220 small dams have been builE and several mediurnsized ones are under construction or planned; they are maintained by a State corporation which operates with contributions from the farmers. - Rural producEion is promoted through Ehe activities of NoRRrp (Northern Regional RuralIntegrated Progranrne), URADEP (Upper Regional Agricultural Development prograrrne) and FASCoM(Farmer's service company). The ii.st iro o.g"rrizations provide technical-advisory services, assist with management, provide loans and, in certain cases, set up ranches, the Eiird is responsible for distribution of fertilizers and equipment. ocP/84.3 Page 66 (d) Burkina Faso (272) In 1974 Burkina Faso seE. up the Volta Valleys Development Authority (AW), a public industrial and corunercial body with legal status and financial autonomy, to exploit the natural resources of the valleys under control. Once a master plan had been drawn up, the next step was construction of a road system linked to the national network, sinking of wells and construction of comrnunal buildings(dispensaries, schools, and housing for supervisory staff) prior to establishment of the undertakings. These are planned to ensure self-sufficiency in food for those working them, provide them with a decent income and al1ow adequate crop rotation. They are some 7 to 10 hectares in size, including fallow and reserve land; the cultivated area is 0.65 hecEares per inhabitant, viz.4.5 hectares for an average family of seven persons. Village and block committees help provide extension services for the villagers and particularly the wonen; adult literacy centres are in operation; shops, including medicine st.ores, are managed by villagers. An agricultural loan service enables them to buy selected seedE, fertilizers, plant health preparations and draught animals. The AW plans to establish zones for non-migraEory stock-raising and peasant reafforestation areas. A 600 hect.are reafforestation project is implementaEion. Environment,al protection activities are also provided for indust.rial and in process of From 1972 to 1981 the AVV received financial assistance in the amount of 10.8 billion CFA francs which was used to cover the expenses incurred not only for the provision of basic education but also for the settlement of 2450 families totalling about 18 000 persons. The 1983-1986 prograrme provides for the settlement of about 10 000 other families at an average cost of 1.5 million CFA francs per family. The villages are grouped into eight blocks situated along the Red Volta (one block), the White Volta (eight blocks) and the Bougouriba (one block). The average yield forecast for an undertaking is 2200 kg of cotton, 1650 kg of sorghum, 1700 kg of milIet and 350 kg of dried vegetables. (e) r'rali (258) In pursuance of agreements concluded with UNDP and FAO in 1978, the Mali authorities established a data bank and a planning unit for the onchocerciasis zone. In ghe preparation of the plans for basic development, t.hree pilot zones with a total population of 3000 were identified, viz: (1) Hount.ounlouga (district of Kati, outside the present OCP area); (2) Denyekoro (district of Dioila); (3) Pikoro-Founa (district of Yorosso). In each of Ehese zones there is an informal coordinating council representing producers and consumers and associating them in the decisions taken by the political and adminisErative authorities. A land occupancy and land aptitude survey has been conducEed in each zone. Activities include the installation of basic equipment (boreholes, PumPs, mills' eEc.) and, where appropriate, experimental inEroduction of fechnologies for production of renewable energy. In addition, over 60 individually planned projects have been idencified and data files prepared for the investors. Some 15 are in process of implementation or have even been torpt"t"a, such as the Selingu6 dam on the Sankarani. They relate to agricultural and food-processing development, renewable energies, road systems and rural infrastructures. Finally, mention must not be onitted of the sEriking developmenE, begun during the EDF campaign before the Prograrnme was launched, of the onchocerciasis-freed zones in the Farako bas in. ocP / 84 .3 Page 67 ( f) Niger (270) Onchocerciasis is confined to the southern part of the district of Say (11 000 km2) on the right bank of the Niger opposite Niamey. It is one of the best-watered regions of Ehe country, with very promising agricultural potential and a population density of only six inhabitants to the krnz. The project for development of the district, prepared with UNDP support when OCP was launched, has not yet been fully implemented. A 300-hectare rice-growing area, which is an extension of the Niamey productivity project, has been established in Say and a market gardening micro-project is in operaEion at the Kobadi€ pond; these projects are not directly connected with onchocerciasis control. A great deal of spontaneous inrnigraEion from Niamey and the districts of Ouallan and Filingrr€ is, however, taking place. This influx is effectively reaching the valleys under control, particularly Ehat of the Sirba. (g) Togo (271) Development of the onchocerciasis zones began in 1976. Ihe large-scale prograrrEne for the Oti Valley is divided into three development projects, one for the Mandouri Plain, one for the Tchiri zone and one for the Niami6l6 Plain. Only t.he last of these is in process of execution with the esEablishment of a hydro-agricultural zone and development of stock-raising, at a cost for t.his first phase of 3.7 billion CFA francs. The reclamation operations in the Kara Valley, begun in 1974, are being supplemented by development of animal-traction farming; over 2 billion CFA francs have been invested in the initial phases of these two projects. The operation for intensification of agriculture in the savanna region, costed at 1.47 billion CFA francs, will provide support services for 2500 undertakings, sith development of the use of animal traction, particularty for cotton-growing. This very effective canpaign is benefiting directly from the Prograrme's achievements. The Atchangbad6-Sirka food production programne, costing 420 million CFA francs, concerns promotion of food-crop growing in 700 undertakings. In all these projects the relevant village infrastrucEures are provided for. The projects, now in preparation, for hydro-agricultural development of the Mono VaIley and rural development of East Mono are located in the southern extension zone of OCP. The former would be implemented jointly with Benin; in addition to producing electricity, che dam thaE. is planned would enable 15 000 hectares to be irrigated. The [Fosse aux Lionst] project, under preparation, near Dapaong provides for construction of a dam on the Koumfab and irrigation of 1500 hectares. 4.3.2 Settlement and bri 1n lands under cultivation In general, the bringing under cultivation of the valleys resulE.s either from supervised settlement as part of the national development programres we have just described or from spontaneous occupation by imnigrants from other areas or from existing villages near the valleys. The spread of individual means of transport in the form of bicycles and mooeds is enabling people to cultivate fields 10 or 15 km from their vitlages of residence. Mbanwhile some farmers build temporary dwellings used during the growing season. Lastly, in some cases, those working new farmlands creaEe neighbourhoods or villages in satellice relationship Eo their villages of origin. Cases where people move in from a village between Ehe rivers generally raise few social problems since in most instances the conrnunities already owned the land in the valleys. In such conditions there is no disruption of the land tenure system. ocP /84.3 page 68 On the other hand, occupation of new lands by migrants from elsewhere (nationals or aliens) can take place only with Ehe agreement or neuErality of the local corununities having traditional tenurl of the 1and. It may entail major social changes. In Burkina Faso it is often the Mossi ethnic SrouP which undertakes such migrations. The extenE of seEtlement and bringing under cultivation of land under control Eherefore varies considerably frorn valley to valley depending on the development plans, population pressure between the rivers, land occupancy and tenure systems, social organizationr etc. In 1983 the Programne recruited four consultants to study the bringing under cultivation since the start of the Prograrune (1975) of a number of valleys in Burkina Faso and Ehe Farako region in Ma1i. (a) Farako Basin Mali ( 193) Between 1952 and 1975 the cultivat.ed areas in the zone subject to flooding increased by 6252 and it is now fully settled. A tea planEation supplies one-sixth of Malits needs. "Dryt'crops continue to increase at the rate of 47" pet year. Cashew nut and tea plantations have been laid out. The village corununities, whose very existence was in jeopardy before the blackfly control campaigns began, are nolt actively expanding. Ihe Farako basin prefigures the course that might, in Ehe medium Eerm, be taken by economic development in certain zones under control. But the model does not, in this sphere, have the same general validity as in epidemiology, for socioeconomic develoPment depends on cultural, social, ecological and political determinants specific to each region. (b) White Vo1ta and Red Volta Basins in Burkina Faso (193) In boEh basins development areas planned by t.he Volta ValleystAuthority (eW) exist alongside spontaneous undertakings. In the 20 years preceding the onchocerciasis control campaign, the growth in land area utilized was 0.2 to 0.32 per year, i.e. less than Burkina Fasors population growEh rate' which is from 1.2 to 2Z per year. The inhabited land area had even diminished by 7.92. Since the start of the Programne the annual increase in areas utilized has averaged L17", making 2237" siace the Prograruue began. In the Yeriba (White Volta) zone, where the expansion has been fastest, the percentage of available land areas actually utilized has risen from 28 to 99i(. The laying out of new fields has acceleraEed over the past five years. In general the number of spontaneous migrants, resident or temporary, is more than twice the number of persons settled by the AVV. A census of two settlemenE zones at Mogtedo on the White Volta showed, out of 2178 families,572 resident families settled by the AW, 75I families of resident spontaneous migrants and 855 families of Eemporary sponEaneous migrant s . The area of each spontaneous farm undertaking is, in general, only half that of Ehe AVV farms. Ihe population density in Ehe AVV zones is from 32 to 35 inhabitants per km2. ( c) Bougouriba and Black Volta Basin in Burkina Faso (217) In the Dagari country, north of the junction of the two rivers, the annual growth in areas utilized is 7.8% per year in the direction of the Black Volta an.d 2.411 it the direction of the Bougouriba. The distance between the forward edge of the cultivaEed area and the river has diminished by half over Ehe past 10 years. These holdings are farmed from the old-established villages, without any new dwelling units being created; this is due to Ehe curse attaching to the valleys ravaged by the sleeping sickness epidemics of 1905 to L935 (79) and to Ehe very strong social cohesion of the populations, which remain grouped in their traditional vi1lages. There are no rnigrants from ot.her ethnic groups. cr.Pl84.3 Page 69 In the Birifor country south of the same junction the annual increase in cultivated areas in the direction of the Bougouriba has been 6.47" and has followed the same patterns as in the Dagari country. In the Lobi country, where population density is low, no extension of cultivated areas Eowards the rivers has been observed. What is more, the inhabitants object to any settlement of migrants. The situation has therefore remained static for 10 years. In Wii16 country rhe situation is of intermediate type, with no nelr villages being created. The development of the AW zone in the Djipologo district on the Bougouriba (six villages, 237 f.amilies) has shown thaE the valleys can be occupied without risk, and a nigratory movement of permanent residenEs into the valleys has arisen in parallel with the AVV sectlements. MosE of these migrants come from the neighbouring villages between the rivers to which the lands belong. The AW is trying Eo channel this movement so as to prevent unconErolled and destructive exploitation of the last unclaimed lands in this region. (d) Samand6ni Region, Burkina Faso ( 175) In the 1960s the cultivated areas represented less Ehan 57" of the total. Since then the increase in areas under culEivation has been 3002, and since 1981 the upper valley of the Black Vo1ta, which was deserted, has been brought. under cultivation. This is the region into which there is considerable Mossi irmnigration. In the Samand6ni region the population increased by 2292 between L977 and L982. (e) Saint-Pierre Region , Burkina Faso (175) In the district as a whole che cultivated area has increased by 6002 and now represents 24.77" of the available land. In the valleys, notably that of Ehe K6ra1i6, almosE the entire cultivable land surface is occupied. The area has been Ehe scene of intensive inrmigration, with creation of new villages. Malians constitute a substantial proportion of this new population, but it was augmented by a large contingent of migrants from Burkina Faso itself, especially between 1975 and 1980; the latter settled in already o1d-established villages. ( f) L6raba Basin Burkina Faso (175) The total culEivaEed area in the district has increased by L2%. The farmlands around the existing villages have expanded and the space along the river is no longer empty of human beings: only a 13 krn zone upstream of the L6raba Bridge remains uninhabited. The new occupants, ofEen naEive to the area, build their dwellings where their undertakings are, creating the nuclei of future villages. (e) Como6 Basin Burkina Faso (175) In 1955 there exisEed two poles of setElement, Saterna and Folonzo, and between them a total void. By 1983 village farmlands had more than doubled. The Como6 valley is occupied by rainy-season fields, and Ehe empty space is filling up, though slowly; the river banks are not yet occupied. There is litt1e irmnigration, but some occupation of valleys by displacement of fields, often temporary. In conclusion, as can be seen from Fig. 18, the higher Ehe population density has been between the rivers, with resultant overcrowding, the more intensive has been the process of occupation of the lands in the valteys. Land has in general been brought under cultivaEion fasEer than villages have been established. Migrations int.o the territory of oEher ethnic Sroups are less frequent and of more recenE occurrence than relocations within the t.erritory of origin. Ihe general process of occupation of the valleys has gathered pace during thepast five years. ocP /84.3 Page 70 5t€tte oHA Ulo cE - I Id o !i .9 3o d s=:a:3 i3 =.EE2 E::; L=lE!4 ar-E < 6.lPg B-ES;>.=tsE =.oook JzoN c -..: ri +a2 FU' oo E o 2 ! s .9 cc .=o ,E! 5 cB. :-o EE A .c= ! ;EEE}: 4: Z;c!==! i r.f I; E---- E :-- 3 3 E E! >E E N ? c9==5 E -!!= = c ?!ESoo!-e-cg=E 4 -E - u iEF - o== - c o o E::E!H il 5is--ll2 =3ee-=./3 EEEIgE = oJoou@- a -..iei<6i@oG I lt a t z T(9 q n o I I a t ,Jo ,()!o .tF al*"". a a o o) E in o a aI ) a at , a 0 a a a a a a a o E o c oz o o o o2 .E €c E o oEoIz oo oa It +t It ilt t:::::::::,\i:.iil t a a 3 33oo o fo = - { o an t! zg E,f oi a't dz o -9oo ts ctz oI oo F & o .= 6 oz s* & C a .= .=I4 UY o IE zoo G ul o3s .t, P LlJ oJ,JEgt r!zo= eg FI 1Agf l!zOY85 = crl z o P 0 tr z I ocP I 84.3 Page 7I The studies conducted in Burkina Faso are the prelude to a comprehensive evaluation of the dynamics of occupation of the valleys since the inception of the Progranune. This study, undertaken by FAO, is being done by comparing Ehe picEures taken by Landsat earth satellice in 1974 and 1983i the results will be avai-lable during 1984. This type of investigation will always need Eo be supplemented by multidisciplinary studies in the field. 4.3.3 Protection of the environment in areas under control The drought t.hat has prevailed in recent years, by accentuating the process of desertificaEion, has alerted world opinion Eo Ehe importance of safeguarding Ehe natural environment so that future generations will have a world fit to live in. Ihe problem is a world-nide one, as is apparent from the multidisciplinary studies conducEed by UNDP (279), but West Africa is one of the regions urhere it is seen as most acute (187). AE Ehe JPC meeting in 1983 (266) several voices were raised to express fear that uncontrolled occupation of the nes lands would cause irreversible damage to ecosystems. The preservation of the tree cover and, in particular, of the gallery foresE was perceived as essential to halt the process of degradation of plant life and maintain the rrat.er cycle. Uncontrolled land clearance and especially felling of trees for firewood pose a severe threat to ligneous resources. Wood is the main if not Ehe sole source of energy used for cooking food and the demand for it grows pari passu with population expansion. Intensive reafforest.aEion is at present the sole means of satisfying these requirements and ensuring that supplies are not obtained solely to the detriment of natural forrnations. Most of rhe States participating in OCP do, in fact, have reafforestation plans, many of them ambitious. The dangers threatening the larger fauna, many species of which were locally becoming extinct, were referred to. Creation of reserves and placing under protection of threatened species were keenly advocated. Some States have increased the area and strengthened the supervision of their reserves. A11 the counrries have hunting legislation enabling certain elements of cheir fauna Eo be protected. Herds of domestic animals must be sErictly managed to prevent. overgrazing by caecle and destruct.ion of young trees by goats and sheep. The attention of the JPCts participants was drawn to the misuse and indiscriminate application of pesticides by certain farmers, causing far-reaching damage to the invertebrate fauna. Moreover, certain insecticides are used as poisons in fishing and are far more harmful than those applied by OCP. NeverEhe1ess, it is sometimes Eo the Programne Ehat abnormal mortality among fish, for which it is in no $ray to blame, is ascribed. Ihe members of Ehe JPC did not attempt to take stock of the ecological problems of WesE Africa, of which those facing the onchocerciasis-controlled zones represent only a small part. They drew attention to Ehe need for organizing, to the fullest extent possible, the development of the new lands so that their chaotic development would not cause irreversible damage to the environment. The Prograrune reminded the States of the wishes expressed by the advisory bodies while at the same time conveying to them its own information on reoccupation of the valleys, particularly by spontaneous migrants. It also decided to assist them by affording granEs for training in agricultural management, environmental management, forestry techniques, stock-raising and sociology in addition to E.he fields in which it was already providing assisEance (see Chapter VI) 4.4 Enhancement of working capacity Ihe analysis done in Burkina Faso after seven years of larviciding showed that onchocerciasis had no effecE on human fertility and little on Ehe demographic pattern. OnIy the blind displayed excess mortality. In hyperendemic zones the mean age of onseE of blindness is 39 years, in mesoendemic zanes 45 years, and in hypoendemic zones bet.ween 49 and 51 years. Sight impairment deEected by the field reducEion test appears still earlier. In hyperendemic zones in particular, therefore, loss of sight occurs at a crucial period in the individual's life, when he is fulIy producEive and often has a big family to support. ocP I 84 .3 Page 72 The life expectancy of a blind person, from the time he loses his sight, is nine years in hyperendemic ,o.t.r ..rd ""*r.n years in mesoendemic zones; it is 13-15 years less than that of sighted persons (120). From the time he loses his sight the individual is unproductive and has no further active life for the conrnunity. Not only Ehat, but he is a burden upon it. Accordingly, in the analysis done in Burkina Faso years lost owing to onchocerciasis were considered t.o include those during which the individual was alive but blind as well as those lost because of premature death. Of Ehose years only part, namely those between 15 and 60 years of age, would have been devoted to a productive activity. In Burkina Faso an evaluation was made of the increase in number of years of life and especially of productive life, i.e. t.he increase in work capacity, which has resulted from thl Progrlrunet! activities. Ihis economic aspect must be considered as well as the considerable humanitarian impact produced by elimination of the terrible handicap of blindness. Before operations began, 500 000 persons were living in hyperendemic zones where the uean blindness rate was 30 to 50 per thousand and could be as high as 130 per thousand in some communities. Another 500 000 persons lived in mesoendemic zonea (112). The annual incidence of blindness ranged from 3 to 11 per thousand in the hyperendemic zones (134) and Ehe mean rate stood at 5 per f0O0 (115); in over 807" of cases it was due to onchocerciasis. In the mesoendemic zones che incidence was 1.8 per t.housand. After OCP operations began some lesions continued t.o progress sPontaneously towards blindness. Since 1980, blindness has been seen only in the form of sporadic cases. By 1981 it was estimated that over 12 000 persons had been saved from blindness and that the figure would have risen to nearly 49 000 by ttre time the Prograune was completed (116). The total number of years of normal life that nill have been gained by the end of the canpaign in 1995 is estimated at 425 OO0, including L45 000 years of productive life with individuals performing their work normally. The cost of the 20 years of campaign for Burkina Faso alone is estimated at US$ 26.82 nillion. Each year of life gained will have cost US$ 63 and each year of active life US$ 184. This figure may appear high, but it is in fact lower than the cost of prevention of measles, estimated at US$ 190 per year of active life. And vaccination against measles is now integrated into primary health care. The increase in work capacity is only one of the Prograrunets many spinoffs but would suftice on its owrl to justify the financial outlay. 4.5 Improvemen t of the livins environment In t.he foregoing paragraphs repeated mention is made of the fact Ehat the economic development projects include the establishment of basic structures: construcEion of a road nerrrork connect.ed to che national sysEem, sinking of wells and in some places provision of piped water, building of schools and dispensaries followed by placement of teachers and nurses, creation of agricultural co-operatives where the peasants can obtain supplies of seed, fertilizers and sometimes essential products. In addition, agricultural development technicians are often assigned to promot,ing the use of draught animals and of new methods in farning. These advanteges attract the inhabiEants of disadvantaged villages where schooling and health care are only very partially provided for. What is more, the bringing under cultivation of Ehe land in the valleys by governmental bodies has shown the local population that the waterside areas could be settled without risk. These lands often lay under a curse according to local tradit.ion (2L7). The memory of the terrible Erypanosomiasis epidemics of the first Ehree decades of the century is invoked, but oEher factors such as blindness and t.he presence of wild animals are probably inprinted in the collective memory of the conmunity. 44 Lastly, the elimination of the nuisance caused by blackfly bites has been a relief for the peasant, whose working conditions have improved out of all recogniEion. Indeed, this is the most irmnediate benefit he has perceived from the activities of OCP, which has proved an unquestionable incentive t.o the cultivation of riverside lands. It is probable that any interruption, without transitional measures, of the larviciding carried out by OCP would at this time be taken very ill by the inhabitants of the previously worst-infested va1leys. Indeed, some villagers are continuing to complain of more or less imaginary bites in the cleared zones for fear that, if chere are no blackfly, the Prograrune will suspend iEs 1 arv ic id ing . 6 OCP and public health 6.1 OCP and the objective of health for all by the year 2000 At present there is no other means of onchocerciasis control Ehan destruction of the vector, since there is no drug suitable for mass use and no one can predict how long this will remain Ehe case. These vector cont,rol operations against the blackfly depend on highly qualified personnel and very sophisticated techniques which must be sErictly planned in time and space and whose implementation goes beyond t,he scope of primary health care. Ihe Progranme, as an essential element of health promotion in West Africa, is therefore necessarily, by the naEure of its operational constraints, a vertical and regional campaign, particularly in its attack phase. The structures and activities of the Prograrune may at first sight appear in contradiction with the general policy of health for all by Ehe year 2000, based on involvement of corrnunities and development of primary health care. In facE, the Progranrne is complement.ary to couununity activities and this type of campaign was allowed for in the joint WHO/UNICEF report to Ehe Alma-Ata Conference (1978)3 I'The support of other leve1s of the health system is necessary to ensure that people enjoy the benefiEs of valid and useful Eechnical knowledge Ehat is too complex or costly to apply routinely Ehrough primary health care.tt In hyperendemic onchocerciasis regions, where blindness may affect. 10% of the population, the elimination of this endemic disease is an essential prerequisite to any health promotion; for the present it can be achieved only through the strategies used by the Prograrune. 4.6.2 The public health s pinoffs of OCP Aside from the ocular, skin or general damage caused by the parasit,e, onchocerciasis impairs cellular irmnunity. Only 25 to 307. of individuals wit.h severe forms of savanna onchocerciasis have a positive tuberculin reaction compared to 70% in a normal population (139). It has been reported that t.he prevalence of leprosy was higher in onchocerciasis patients, but this statement would need to be checked in detail. In fact, the consequences of t.his lowering of cellular inununity have not really been studied, so the advantages of its restoration cannot be evaluated. Probably it has been indirectly, by stimulating economic development, that the Progranme has mosE influenced the health level of the populatioos. fhe establishment of primary health care centres in most of Ehe zones developed gives the population access to care and medicines that were not available to them in their isolated villages. The increase in incomes enablespeople to buy essential drugs and to treat Ehemselves. For example, in the region of Bobo-Dioulasso, ac Samandeni in particular, the population, freed from t.he burden of onchocerciasis, extensively practice self-treatment of fever cases with chloroquine. Thispractice, associated with the activities of Ehe dispensaries, reduces mortality from -alaria to a very low level. ocP I 84.3 page 73 AI Furthermore, the agricultural output of the undertakings, supervised or spontaneous,gives the farmers self-sufficiency in food and allows them to sell part of their produce.this time of growing concern as to how the populat.ion of the Sahel lountries is to be fed, the contribution of the lands under onchocerciasis control is of significant help towards solving the local and national nutritional problems. The indirect benefits of the Programme t.o the health of the populations are in any case only one specific aspect. of the reciprocal relaEions beEween economic development and level of health. ocP/84.3 Page 74 4.6.3 Involvement of co"rmunities in OCP At the present stage in rhe battle against onchocerciasis, the involvement of cormnunities is not a det,ermining fact.or in t.he success of the operation. But in the medium and long term, when the changed epidemiological panorama aIlows Ehe means deployed by the Prograrme to be reduced, the control or at least surveillance acEivities will be devolved to the national health services. Hence cormnunity action will be essenEial, especially if effective drugs are developed. Since Ehe inception of the Prograrune, those directing it have shown a constant wish to involve the various social elements of the corununities with their activities in all spheres where it was found possible. (a) Inforruing the public and the authorities Operating through the press and health education services, an information campaign was start.ed in 1975 to make the populations arrare of the dangers of onchocerciasis. Posters as well as the media were used to publicize iE. The contact that OCP staff have with the villagers helped Eo make this operation a success. The cornmunities r.rere very soon able Eo understand the relationships between the blackfly and blindness, together with the objectives of the Programue. Thus Ehe intervention of the aeroplanes and helicopters was very well received. fhe elimination of blackfly bites gave people confidence in the usefulness and soundness of the vecEor control measures. The information effort was not directed only to the populations at risk, but also to the authorities, thereby winning their unconditional support. It has also been directed Eo the donor countries, anxious to keep abreast of the progress of a campaign Lo which they have given their backing. Although the medical profession have supported the Prograrme, some reservations have been expressed about the fact that patienEs are not sysEematically treated. It must be stressed that Ehis negative feature is due soleIy and simply to the absence of any effecEive and easily administered drug. Fully aware of the need to have a therapeutic arsenal available, the Progran-e aciords very substantial subsidies to research in chemotherapy (see section 5.4) precisely with a view to being able to treat onchocerciasis successfully and possibly find a chemical means of preventing it. (b) Participation in epidemiological evaluation surveys Longitudinal surveys are Ehe cornerstone of epidemiological evaluation. It is therefore essengial Ehat the same population sample should present at several yearsr interval for the parasiEological and ophthalmological examinations performed by OCP teams. So far each village has been visited two or three Eimes. Ihough these examinations are not painful, they are a demand on the paEientis time and there must be cooperation by the population if the sample is to be numerically and qualitatively sufficient for a meaningful interpretation to be made. The assisEance of the peripheral stations of the health services, of volunteer workers or of corununity leaders is needed to Eotivate the populaEion to attend the examination 6essions uncoerced. It is Ehe responsibility of OCP teams Eo ensure Ehat Ehe population's confidence is maintained. The success of the Prograruoe has been such that in some conrnunities the memory of onchocerciasis and particularly of the blackfly nuisance has faded. The problem is regarded as settled. Thus Ehe population may no longer see any point in presenting for examinations. The propaganda effort musE be kept up so that the epidemiological and ophthalmological evaLuation can be conducted under ProPer conditions. (c) Participation in rrater resources development Some features of water resources development, notably dam spillways and irrigation canals, are liable to create S. darurosum breeding sites in regions where Ehere were few or no blackfiies and give rise to sEilous epiaemiological situations. These disadvantages can be t ocP/84.3 PaBe 75 t mitigated by appropriate devices installed when the construction work is done (see section 5.3) and an information effort directed Eo the development pronoters is therefore necessary. Even when such measureg have not been taken at the proper time, however, the users can intervene to good effect. By closing the spillway sluices, they can periodically dry out thedrainage canals and kil1 the blackfly larvae by dlhydration. PLformance of thesl simple actions nevertheless calls for sound knowledge of blackfly biology; it necessitates supervision by professionals or by volunteers who have had some training. The first experiments on these lines are in progress in the Dogon region in Mali (104, 260). (d) Participation in entouological evaluation In this very same Dogon region, the Prograrune (260) has turned to account the seasonal nature of the transmission and geographical limitation of the prevalence of onchocerciasis, plus the Presence of a body of motivated voluntary first-aid sorkers and a dynamic and respected extension officer, to try and interest the population in the control of this disease. OCP has at its disposal there a permanent infrastructure for entomological evaluation and treatment of blackfly breeding sites. These sites are few in number, tenPorery and with low discharge ratee and can therefore be treated economically fron theground. Side by side with OCP staff, the voluntary first-aid workers assist with thelarviciding, help collect larvae and monitor the traps, give the alarm when flareups in Ehebiting activity of blackflies are observed, and take hydrological and rainfall readings. This successful experiment is being continued to determine which activities can be assigned to these co*unity officers when devolution takes place. An experiment in entrusting the monitoring of traps (aluminium plate type) to the villagers has been tried out in the south-rrestern part of Burkina Faso. The initial results have been prornising. (e) The future of contmunity participation NeverEheless, no general conclusions should be drarrn from experience in the Dogon region, for the enEomological situation is exceptionally, indeed uniquely favourable in the Prograrme area. Moreover, the social structure has been very conducive to motivation of thepopulation. I,ltrat this exaople does shorr is that the Prograrune is concerned to promote comunity participation everywtrere and in all possible spheres. In a survey conducted by tlHO anong the States to investigate the possibilities of involvement of the co-unities in the various forms of vector conErol, it was proposed that individuals subjecEed to blackfly bites should be protected by wearing special clothing. That seems very difficulc as most people are infected at their places of sork during the hottest hours of the day wtren to rrear such clothing, costly in any case, would be unbearable. Repellents of loca1 origin have been advocated: palm oil, perhaps with certain ingredients added, displays a certain repellent effect which is now being studied (2LZ). Unless uajor new discoveries, notably in the sphere of mass chemotherapy, are made in the near future, onchocerciasis control rcill continue in the coming decades Eo require theintervention of specialized personnel belonging to OCP or to national services. To these specialists the co*unities will afford their support, but they will probably not be able to take their place. 4.7 conclusions regarding irnpact of ocp in the socioeconomic sphere 1. The Onchocerciasis Control Prograrune has everywhere had a stimulating effecE on socioeconomic development, to judge by the increasing number of development projects drawn uP. The types of action vary from country to count,ry. Burkina Faso has established a specific structure (the AVV) for the developoent of Ehe valleys under onchocerciasis control. 2. In Burkina Faso, aside from their own dynamics, the AWrs development zones have prompted a greet deal of spontaneous settlement through their catalytic action. 3. The elimination of blindness considerably increases the work capacity of the populations. It would on it.s own justify the amounts invested in the Progranme. ocP I 84.3 Page 76 4. The programme has considerably improved the living environment of the inhabitants of the valleys by eiirninating the blackfly nuisance. The development of basic facilities such as roads, scirools, dispensaries, agricultural equipment, etc. which accomPanies the development projects has made an appreciable contribution to the upgrading of rural life. 5. The prograrrne is a prelude to Ehe establishment of decentralized health activities. Its objective is to eliminate a disease against which the curaEive methods applicable_at the peiipheral echelons of the health services or at the directing Ievel are ineffective. In addition, its economic spinoffs contribute to the solution of nutritional problems. 6. The governments and corrrmunities have been informed of the objectives and progress of the prograruneis activities and this has enabled their cooperation Eo be secured for the epilemiological surveys. A11 the spheres in which the conrmuniEies can participate in the conErol of onchocerciasis are being explored in anticipation of the devolution of the Programnets acEivities to the participating StaEes. , ocPl84.3 Page 77 I CHAPTER V RESEARCH CONDUCTED AND SUPPORTED BY OCP 5.1 The role of research in OCP The Progranune of course took advantage of the lessons learned from previous operations, and in particular the EDF/OCCGE campaigns (see section 1.1), to determine its strategy andits evaluation meEhods, but it has needed to innovate in all fields so as to create the necessary sEructures and tools for attaining its objectives. The whole Prograrme can, without exaggeration, be considered as an operation;1 research exercise. The establishment of the limits of the Prograune area rras one of Ehe first matters E.o be considered; it has come up again with each request for extension and, a fortiori r1f, connection wich the working out of a long-term strategy (see sections I.4 and 3J ). The putting into operation of entomological, epidemiological, ophEhalmological and hydrobiological moniEoring, together with the transmission and storage of information, has been approached in an innovative spirit, adapting the undertaking to the scale and requirements of OCP. Adaptation of the larviciding techniques and apparatus to the different types of insecticide used necessitates ongoing research since OCP has no similar operations Eo referto. Specific methodologies have had to be creaEed for Ehe studies on reinvasion and resistance and for surveillance of Ehe aquaEic environment, and their results not onlyprovide informaEion necessary for the proper functioning of the Prograruue but constitlte an invaluable contribution to knowledge of river ecosystems and blackfly bioecologi'. The epidemiological and ophthalmological evaluation of the Prograrme constitutes the most ext.ensive study yeE conducted on the transmission, epidemiology and ocular manifestations of onchocerciasis. The interruption or attenuation of transmission has provided a unique opportuniEy for observing the kinetics of the reduction of parasite loads. The socioeconomic and health development spinoffs of the Progranrme open up an almost untouched field of investigation that will be a neeting ground for many complementarydisciplines in the medical, social and economic sciences. fhe study o.t th" connectionsbetween human ecology and onchocerciasis is an example of this type of interdisciplinary research. Finally, the definition of a lon5Eerm strategy and the identification of the human and material means and the budgetary resources needed to carry it out constitute an exercise calling for the creative spirit which is characteristic oi all research. Ttris being so, why include a special chapter on research, which is in fact very short in relaEion to the acEual role of oCP in this field? Mainly in order to describe work performedby the Progranrners teams or by collaborating laboratories which is not part of theProgranuners daily round but is designed to provide the necessary tools ior its development..Like most demarcations, Ehis is an arbitrary one, and the sections devoted to reinvasion, resisEance, monitoring of Ehe aquaEic environmenE, even epidemiology and ophthalmology andthe studies on human ecology, could easily be put under the heading-of ttnesearcht,. Grouped together in this fifth chapter, therefore, are the studies on the taxonomy andbioecology.of the vectors and then on the means of destroying Ehem, i.e. the development of new insecticides and new control methods. After that, menti6n is made of the work Leing doneon the parasite and on chemotherapy. ocP/84.3 Page 78 5.2 Studies on the vector Simulium damnosum s.1. 5.2.L Taxonomy and distributioq 5.2.1.1 Cytotaxonomy and distribution of species It had been known since 1966 (46) that the name Simulium damnosum lumped together a number of forms, morphologically closely related but distinguishable by examination of the polytene chromosomes of the salivary glands. To date 28 forrns have been described in the S. damnosum complex (46). Eight of then have been observed in West Africa and were given in 1975 (157) specific designa t.ions: S. dieguerense S. sanctipauli S. soubrense, S. squamosum, S. yahense, !!ry s.s. name is now tacitly regarded as synonymous ,S . sI.,rbanum and S. sudanense. Thi.s last species w1 th the preceding one. Cytotaxonomy provides the reference criteria for identification of blackfly of the S. darnnosum complex; in the light of these there was drawn up in 1981 (90,126,127, L58, 209) a map showing the distribution of the different species in West Africa (Fig. 19), more complete than the 1978 version. It includes regions outside the presenL Programme area scheduled for an eventual extension of operations. In fact the situation is still more complex than the initial studies showed. S. sanctipauli and S. soubrense are considered as two forms of a variable species which includes trro other 6rmi]-otkour6" in Guinea and "Beffa" in Togo. This latter is their chromosomes. In the Ivory Coast, S. soqllenee is the most frequent form of the grouP in savanna and preforest areas, whereas s anc t ]-pau i is dominant in the southern forest , interfertile with S. sanctipauli of the Ivory Coast.. A series of west-east and norEh-south "clines" are obserE6llf6ffi-the different forms (fig. 19), reflected in the inversions of zone; in zones where there is contact Uetween ttre trdo forms up to 5O7. of hybrids may found (90). be S. uamosum distr 10n: sma occupies widely varying habitats in the various Parts of its area of 11 forest streams in Liberia and the Ivory Coast, savanna uatercourses in Togo and Benin, great rivers like the Congo in cenEral Africa. These ecological differences are reflected in the polymorphism of the inversions. Whether this is, in fact, a single species has, therefore, been strongly called in question. The duality of S. darrrosum and S. sirbanum is recognized by all auEhors. S. sirbanum is ^.@7,the doninanE species in the temporary watercourses of the norEhern Programme158, 209). S. diegupre4re has been found only in the Senegal river basin, outside the presenE Prograrme area. It has been possible to follow for several years the evolution of the genetic characteristics of the populations. In the lower Sassandra and Bandama basins, the frequency of inversion s in S. sanctipaulr has not changed since 1968, which shows the stability and sedentary nature of the populations. S. soubrense, on the other hand, has a more definite propensity to dispersion: an insecticiae-re"istant population, exhibiting characteristic inversion, migrated from the Ivory Coast to Ghana in the absence of any insecticide Pressure. Betrreen 1981 and 1983 the frequency of inversions changed markedly in Ehe populations of S. damnosum s.sEr. and S. sirbanum of the Pro gramne area and also in invading females. In particular, one inversion which would seem to be linked to shortening of the duration of larval development became far more frequent, rising from 0 to 60Z in some cases. It cannot yet, be said whether this rePresents a cyclical insecticide pressure (90). process or a phenomenon resulting from There are seasonal variations in the respective proportions of the various species at one and the same site. For example, on the lower Mono in Togo, the proportion of S. damnosun comP ared to S. soubrense (Beffa form) is far higher in the dry than the rainy season (226), QCP 184.3 Page 79 $ li ir :ll !li :ir :ir!:l :l -| 1l It ,l ,li rlt .il I rl i i i i I I i I !r \: t. \ Y\ I I I I "'11^^ --'a I ,''{ Y-.a-- F\ "- f _t t- I \ I I I( I \ I .\ ;t i xU E . oo EI ,ldcl EI alEI el .=l ,l EI 6l lu F E o o UJc FoF C' B o 2o trf a EFo 5 O I L ,( b -t -?< -\ I( ) trllf \ I I I I I I I I I I I I I .l I I t( /1 .* lrfi-.- (,1 t et I I 'f ntu! n fl5i: \ I I l ,l ! ,d url 'r 5l gg ] I 5 a \r .jrr 4< ',]ri 8.*- ) T,1tr a ocP/84.3 Pete 80 5.2.1.2 llorphologv of blackflv of the S. dernnosum conplex The Programoe has strongly encoura6ed research studies on morphological cheracters enabling specimens to be identified in the field. No good differential feature has been found in eggs or nynnphs. But the lervae of the three species pairs of tJest Africa(S. demnosum s. str/Slglgggnr, and S. squsmosum/S. vahense) can be differentiated eccording to the shape and arrang,ement of the scales of the last abdoninal segnent and the size of the dorsel tubercles (L23, L281. The numerous studies conducted (22,58, 101, L23, L29, 130) on cheracters for identifying biting fenales have only partly solved the problen: there are no clear norphological charecters enebling the sir forrns of the compler to be distinguished. By using a cornbinetion of characters: colour and shape of antennae, colour of wing tufLs, colour of scutellar and postcranial hairs, ratio of length of antennae to length of thorax - it is possible in certain parts of the ProBreme erea to seperate these species pairs. But all specimens cannot be identified with certainty. fhus, in the sestern part of the Progranne area nost flies with pale wing tufts belonged to the S. damnoeum/S. sirbenun pair, whereas flies uith dark tufts never belonged to those species. This character, rhich is easily observed (78), is taken into account by the teems of the subsectors io their routine dissections and has enabled keeping track of the expansion of S. soubrense populetions resistent to organophosphorus conpounds in the Ivory Coest. But this criterion of wing coloretion is of little value in Iogo and Benin where the "Beffa" foro andS. gquamosum, which is very ebundant, may have pele wing tufts. There, identification is very difficult and the other morphological criteria indicated above rnust be resorted to. ldentificetion of the verious forms is mede difficult by the very close kinship between the two forms or species which make up each pair and also by the variebility of specimens of certain taxons, particulerly S. squsmosurn end S. soubrense; this variability is perhaps only a reflection of the fragrnentation of these species within a Eenus undergoing ective evolution and diversification. 5 .2.1.3 Biochemicel techniques in tarononv Electrophoretic anelysis of enz3rmes applied to blackfly larvae, n3nnphs and adults has provided only very limited inforrnation. Out of the 44 systems tested only two phosphoglucomutase and trehalase, heve diagnostic value. Only S. vahense and g.jllgBnosum can be distinguished from one rnother end separated fron the other four forns in the comp1ex.Ineddition,bytreha1asee1ectrophoresis'the@strainsinTogocanbe seperated from those in the Ivory Coast, which confirms their genetic isolation (89). l{osquito populations resistant to organophosporus conpounds can be seperated from susceptible populations by study of esterases (99). It has not proved possible to diagnose resistence in S. damnosun s.1. by application of this nethod, probebly owing to poly:morphisur in the esterase activity end the nultifactorial nature of such resistance. Study of cuticular hydrocarbons by gas chromatography hes shown differences between S. Equqtloguln and S. sirbanun whose taxonomic value has not yet been deternined (19). The other species of the complex have not been studied. Taxonornic studies on the S. demnosum compler heve been faciliteted by the development of techniques for rearing individual broods in the laborabory. The lervee and adults thus obtained ere of the sene size as those collected in nature end can be used for chronosone studies and hybridetion (131). 5.2.2 Biolselogy rsd sempling of oreadult stases At the inception of oCP, the information then evailable on the distribution and ecology of the preadult stages was considered sufficient for the implementation of control operations. The success of those operations has shown the soundness of this vies. The investigations conducted in the past 1O years hed been notiveted by the wish to inrprove treatment evaluation techniques and the need to learn about the behaviour of larvae in relation to insecticide. fn additlon, monitoring of the aquatic environnent has greatly added to our knowledge of blackfly Iarval eco1o6,y. , I I ocP/84.3 p.ge 81 I I I I 5 .2 .2.L Sernplinr techniques Exeminetion of the natural mineral or plant substretes to which the larvee ettach themselves tells only whether or not lervae ere present, though this infornation is very useful for evaluating the results of insecticide treetment, whether erperimentsl or operationel. It is in fect e method regulerly used in the Progranune (see section 2.1). Applied to large samples on well-mapped river stretches the nethod can becone semi-quentitative (47, L46l . Periodic collection of larvae from rocks using the Surber sanpling device nekes long-terrn surveillence of the blackflies possible. Collection of drifting netter in nets provides information on the nycthemeral rhythn or the inwrediate impact of an insecticide. Artificial substrates (plastic tepes, broons, gradueted posts and flag-panels)(47, 50, 54) provide quentitative and reproducible data, very useful for ecological studies. oring, to the fluctuations in river levels and the aggregetive distribution of S. dennosun larvee, there is no method by which its population sizes can be estimEted. 5.?.2.2 Ecolotv of preadult stares The preadult stages of S. dannosun s.1. are g,enerally anchored to plant substrates or rocks imrrersed 40 cm or less below the weter surface; they heve in fact been found at depths of up to 4 metres but it is not knorn how frequent this distribution is and hou viable are specimens living et such depths. The presence of cyanophycean algae prevents colonization of substrates. The etBs ere rerely deposited on rocks (41,50,54,80, 146). The larvae live preferentially in currents of 0.70 to 2.00 n/second but they heve been observed in slower and faster currents ranging fron 0.10 to 2.50 m/second. The different species of the s. dannosum cornplex are not differentiated by their preferred current speeds; however, S. sirbanurn can colonize quite slow currents in the northern part of its area of distribution (54, 80, 146). The eggs ere laid in the fastest current upstream fron the line of breeding places and the blackfly larvae colonize the substrates downstreen by driftin6 (47, 54). Blackfly lervee have two activity peeks, in the morning end the late afternoon; the maximua drift occurs around E p.m.; Iarvel exuviation tekes plece at the end of the afternoon (53). Anong the physicochemicel cherecteristics of the water, only the pH might play e role in the distribution of the verious species of the comp Ier. S. squanos!!!! and S. vahense populate watercourses with en ecid pH (124, 158), whereas the other species are found in more basic environnents. Nowhere in the Programue aree is the water temperature en obstacle to the development of S. dannosurn s.1. (L23, L25, L271. 5 .2 .2.3 Preedult cvcle The duration of the preadult cycle veries according to season, region and speciesGenerally, the higher the water temperature, the faster it is. In the Senegal basin, during the dry s€eson, the preadult development of S. sirbalrun takes sir-and-e-half to nine days when the weter is et 31'C: 24 hours for hetching, 4 to 5 days for larval life end 1.5 to 2 days for pupel life (145). In Higer, during the cool season, it can take as long es 14 to 15 days (173). In forest country in the Ivory Coast, the duration of larvaI life 8 deys in l{ay and 12 days in Decenber. in S. soubrense is In the EDF/OCCGE Protreme, pupae were observed only eight days after larviciding ocP/84 .3 PsBe 82 The weekly periodicity of larviciding is therefore well suited to the duration of thelarvel life of blackfly belonging to the S. damnosum complex; and there is no evidence that any epplications have been ineffective owing to over-repid developnent of the larvee, even in the northern Prograrune regions where S. sirbgnum is abundent. 5.?.2.4 Nutrition of larvae Bleckfly ere,passive filterers": etteched to their substrates, they trap with theirpremandibular heirs the particulate matter drawn elong by the current and ingest it. This uninterrupted ingurgetetion of particles, amounting to dornright .,stuffingi,, pushes the elimentary bolus along. The transit of the bolus takes frour 2 to 40 minutes, depending on the size of the lerve and hence the length of its digestive tube. During this relativelybrief transit the larva absorbs the nutrient substances end with them any insecticides,particulate or adsorbed on clay perticles. The rnarimum size of the particles ingested rentes from 13 nicrons for the first stage to 150 microns for the seventh (37, 51). But a major part of the alimentary bolus of all stages consists of small particles of less than 3 microns end even colloidal constituents of 0.2 to 1 micron (87); these smelI particles ere captured by adhesion to the nucus shich coats the mouth parts (137). The composition of the particles does not seen to be a discriminative factor in their absorpt ion . Knowledge about the ingestion and digestion of nutrients by blackfly lervae is therefore essential for the development of insecticide fornulations to control these insects. 5.2.2.5 Dvnamics of lerval populations The main competitors of the larvae of S. darnnosum s.1. for occupation of substrates are other species of b1ackfly, S. adersi and S. schoutedeni, which proliferete when the former speciesise1iminated.Afterinsecticidetreatmentceases,@isthefirstspecies to repopulete the substrates (47). The presence of elgae on the substretes discourages colonization by the bleckfly lervae The predators, mostly Trichoptera larvae, ere opportunists which by no means confine thenselves to bleckfly elthough they capture these lervae when they are drifting. The repercussions on blackfly dynanics of natural parasite infestation by nematodes of the family ltermithidae or by llicrosporidia have not been evalueted. However, even habitats where a large proportion of the lervae ere infested still have large blackfly populetions (92). The amount of food carried down by the river is enother factor that nray linit the larval populations of S. damnosum s.L unless it is offset by current speed (103). NeturaL selection is very strong; it has been estimated that in the dry season only 2.8a of the eggs laid survive to the nyrnrphal stege (53). However, in view of the number of variebles involved this estimate should be viewed with caution. At high water both the mean current speed end the erea under water ere increesed; these two fectors contribute to the formation end expension of the larvaI habitats. Horeover, the food carried down by rivers is very plentiful. This results on the whole, in a considerable increase in the numbers of lervae and subsequently of edult blackfly. tJhen the waters recede the regression of the larval habitets leads to a reduction in the number of larvae end subsequently of adults. The varietions in the discharge of the watercourses are therefore responsible for the seesonal petterns of S. damnosum (20, 103). The seesonal rivers eppeer to become colonized by waiting migrant females as soon as the water starts to flow. fn the Sahel S. sirbanum eggs have been found two hours after the rivers began flowing (145). ln g,eneral, supports placed in fevourable currents ere colonized within 24 hours by drifting larvee or ett clutches (47,54, L221. t ocP/84.3 Page 83 Finally, certain civil engineering works (bridges, artificial fords, dam spillways, crrals, sluices, etc.) can induce acceleraEion of currents, leading Eo the creation of S. damnosum breeding siEes, while others (dam lakes) result in their eliminaEion (I03 , 104). 5.2.3 Bioecology and sampl ing of adult blackfly 5.2.3.1 Sampling methods CaPture on human bait is still the sampling method most used. It enables Lhe collection of anthropophilic females in search of a host and is at present irreplaceable for evaluating ',he intensity of transmission. But it is insufficient for ecological research and necessiE.ates a large staff. OCP has accordingly been supporting research on trapping with the dual objective of providing itself with effective tools, so that the net\rorks of capturers can be reduced in density, and exploring the ecology of S. darmrosum s.1. adults. Traps can function itpassively" or selectively attract certain categories of insect by olfactory or visual stimuli. The firsE category includes the interception traps: adhesive-covered sheets of transparent glass or plastic positioned across the rdatercourses or among the vegetation. They enable the study of the rouEes and Eimes of travel of blackflies at all stages of Eheir adult life. They are troublesome to use and the results are ofEen meagre (10). Into t.he same cat.egory fatl adhesive-covered supporEs imitating Ehe various features of the vegetat.ion. Considered as lures, they are the best tools yet available for sEudying the resting places of blackflies. Their relatively low yield probably reflects the very wide dispersion of gorged blackflies arnidst all the vegetation of the forest galleries (11, 13). To the second category belong adhesive-covered aluminium plates (09). Positioned near the sites of oviposition, they attract by their sheen Ehe females coming to Iay. Their siting is therefore very important. Up to now it is these traps which have given the best yields, particularly in the dry season. In Ehat period more females are collected on each plate than are taken by a capturer, and someEimes they detect the presence of flies shen catches on man are negative. This may be due either to the greater capacity of the trap for detecting 1ow densities, or to its aptitude for collection of non-anthropophilic females. Ttrese traps are in course of evaluation as sentinels that could enable the entonological monitoring network to be sliruned down (18). So that they will noE be submerged at high r{,ater tine, the plates have been mounted on floats. Research is at present being conducted by the Programe, in collaboration with the Institut de Recherche sur la Trypanosomiase et lrOnchocercose at Bouake, to try to render this trap operational, particularly in the rainy season. Hitherfo its best perform:nce has been detecting the arrival of migranc blackfly at their oviposition siEes before they had laid and fed again (18). Many other types of trap have been tested, but their performances have been less good or their use has proved irnpossible in the field. This applies in parEicular to traps which use carbon dioxide to attract blackflies and which, while giving a good yield, cannot be used beside Ehe rivers of Ehe Prograrme area for logistic and operating-cosE reasons. 5.2.3.2 Ecology of adult blackflies The emergence of the adults, i.e., when they coue out of the pupa after their retamorphosis and the insect goes over from aquatic to aerial life, takes place in the mornings and evenings, with a preference for one period or the other depending on season (16). After the emergence copulation takes p1ace. It was already knosn that the females of S. darrrosum s.1. took their blood meals aE all hours of the day. When Ehe temperature is verf[Q6]]-aETve 30"c, biting activity is manifested in the morning and late afternoon and diminishes around rnidday. When the Eenperature is below 25'C, on the other hand, it is in the middle of the day EhaE the females are most active (80). While this general pattern is not. called in question, it has been shown that hours of activity vary between species in the compparticular, displays an evening peak in the forest <232). lexl S. soubrense, in ocPl84.3 Psge 84 The males and over 50a of the nulliparous and parous femeles take neals of sugary juice(rnostly necter from flowers) to meet their need for enerty foods; digesting this carbohydrate neal tekes 24 hours (L2, 146, 165 ) . The blood meal provides the female with the proteins needed for the development of the egts, The species of the S. dannosunr cornplex ere in general amphophilous, meaning thet while they bite man, they cen elso feed on animals. The percentage of zoophily varies eccordiug to species, region and evailebility of hosts. In the northern part of its eree of distribution S-_C_i_rbenuro displays a very merked tendency to zoophilia, which makes it an efficient vector of snimal species of onchocerca, whose infective larvee must not be confused with those of Parasitesofhumanorigin(35,97,1o3,146,173).Inforestcountry,@,9.I.i-is nerkedly zoophilic in the Ivory Coest 1owlands. tdith S. soubrense zoophilia seems to increase in the northern part of its area of distribution (14, ?32,2341. The duration of the gonotrophic cycle in the field hes been determined by markints, release and recapture of femeles. the tine-lapse between laying and taking the blood neel(phrse I of the cycle) is less than 24 hours; the period of meturetion of the eggs, concomitant with the digestion of the blood (phase II), lests two to four deys depending on the arubient temperature; the search for an oviposition site (phese III) is very short. on averate the duretion of the gonotrophic cycle can be estimeted et four days and there is good gonotrophic concordance, i.e., each neal results in neturation of the eggs of one cycle (12,3L, 80). These results have been confirmed by laboratory tests (27). The resting, places of femeles of the S. damnosum compler long remained mysterious apert fron a few specimens collected in shelters under rocks (102). The utilization of traps simulating natural supports hes shosn that adults, male and female, are found in all strete of the riverine vegetation over a breadth of 1OO metres. The gorged and gravid fenales stay in the hig,her strata. Before laying the grevid feneles epperently cluster in the evening near the oviposition sites, but it is not yet knorn whether they rest on the vegetetion before laying (45, 150, 146, 165). Oviposition takes place between 15 and 90 ninutes before sunset. The fenales looking for the most fevorable site skin over the weter in the opposite direction to the current and deposit their eggs in the upstream part of the rapids, preferentially on light-coloured supports (13, 103). ft was known before the Progranme begen thet blackfly dispersed, starting fron their sites of emertence, along the river (linear dispersion) and perpendicularly to it (radial dispersion). These dispersions were much greater in forests then in savanna country and in the rainy than in the dry season (80, 102). The studies conducted since 1975 heve added precision to these data (17, 31, 2321. IL has also been found that movenents of herds and perhaps of humen beings could induce concentrations of blackfly et a distance fron their breeding sites (146). Long-distance nrigrations and the redispersion of migrent flies frour their oviposition sites have been described in Chapter fI (see section 2.3.1). 5.2.3.3 Dvnanics of adult populations (a) Longevity of females The parous females, i.e., those which have alreedy laid, cen be sepereted fron the nulliparous ones by the presence of remains of follicles, the ebsence or reduction of the abdoninal fat body and the relative thinning out end changed appeerence of the nalpighian tubes (80, 86, 102). It is not yet possible to determine how nany times each parous female hes laid, though some authors heve tried to estinrete this frour the nnnber of ovocytes in course of meturetion in the ovary, which become fewer with age (91); but the number of ovocytes varies with the size of the fly, which detracts from of the value of this method(231. Research is in prog,ress to determine the ag,e of blackflies fron the cuticular grorth layers (95 ) . It was known thet the deily survival rete, calculated from the parous rate, was higher in the savenne (0.91) than in the forest (0.64) and in the dry seeson than the rainy seeson(80,102). It has been shown to be higher in the sevanne species S. dannosum s.s./ ocPl84.3 Patc 85 S. siEDenqtr than in the forest forms S. soubrense/S- senctioelr1i rate may Ue as 1ow as 2OB. By contrast, with S' Yahense in the I rete for S-J-@-sugl s.s. in the sevenna (1O2, L23, 233, 2341 . . In these latter the Perous forest it is similar to the The absolute longevity of S. dannosurn s.1. observed after insecticide treatment of larval hebitats, is between three and four weeks, during which tine the females ceo complete five gonotrophic cycles (31). These observetions tally with the extrapolations mede previously on the besis of the Parous rate (80' 102). (b) Fertility The number of eggs, identical in each of the two overies, rentes on averete fron 4OO to 600 (lirnit values 90 and 1123). Fertility is higher in the forest than the sevanna species. ilulliparous females ere nore fertile than parous ones (15' 21). (c) Variations in size of adult blackfly populetions The s ize of the adult populations is directly related to that of the larval populetion (102). It has no connection with longevity: indeed, it is during the rainy seeson when longevity is lowest that the populetions are largest. On the large forest wetercourses there is a direct reletionship between the level of the river and the abundance of S. soubrense/S. sanctipauli. On the small forest watercourses the populetions of S. yahense remain stable throughout the year. In the savsnna' while the density of S. dennosun/S. sirbanum varies in close correlation with the ueter level, the presence of highly productive dry-season breeding sites results 1oca1ly in there being large populations of these flies. Lastly, in the same localities blackfly density can display a binrodal pettern, with one peak in the rainy seeson and enother in the dry season. 5.2.4 Reerin: of S. dannosun s.1. For many years investigators heve been able to obtain, sterting froru gravid fenales or eggs, developnrent of bleckflies through to the production of edults of the nert generetion. A nethod applicable in the field has been developed in the Protremne. It has enabled, starting from femeles captured in neture, larvae to be obtained for cytotexononic identifications or insecticide-resistance tests (131). t{ating in ceptivity is very difficult to obtaln and this constitutes one of the main obstacles to the establishnent of self-sustaining blackfly colonies. Though e fer matings have been observed between S, oslltn s pecimens fron Ghane, the rate of insemination ia the cage did not exceed 1A (131). A technique of induced copuletion brought the inseninetion rate up from 0.4 to 7A in S. damnosunr s.1. from the seme place of origin. On the other hand, an inseninetion rate of 5OA was successfully obtained with the Beffa forn originating from llono, in Togo (147, 148). The triggering of oviposition hes been improved by sinulating tuilight (27,1471. Gorging on enimals hes given better results than on membranes. Starting fron 7700 eggs of the Beffe form of S. soubrense, five successive generations were successfully obteined in a laboratory in the United States. But by the fourth generation the ser retio had changed and there were only 7a of meles (147). At Akosombo it has twice been possible to achieve reproduction of a very small number of blackflies for three and five generations in succession (131). 5.2.5 The vector role of the various species of the S. dannosum conpler The evidence of differing, degrees of severity in onchocerciesis, corresponding geographically to the distribution of the various forrns of the S. dannosun compler, hes prompted a great nreny studies, in leboretory and field, to detennine the present and potential vector role of each species in the conpler. These studies have been end ere still hanpered by uncertainty as to the stetus of Onchocerca volvulus (see sections 3.3 aod 5.4). 5.2.5.1 Erperimentel transmission The studies conducted since 1975 ere the continuation of previous ones fron which it is difficult to separate them. Their corrnon obJective is to elucidete the problen of the role of the different species of blackfly in the transmlsslon of the dlfferent forms of onchocerciesis. ocP/84 .3 P8g,e 86 Volunteers suffering from onchocerciasis contracted in the forest or savanna were subjected to the bites of blackfly both in their countries of origin and in other bioclirnatic zones where the btackfly species were different. The sir sPecies of the S. demnosum complex are efficient vectors of the onchocerca streins of their regions of origin. At the end of the cycle the mean number of infectivelarvee carried by 1000 surviving fenrales fed on carriers of such paresite is 1350 for s nse , 1050 for S. sanctipauli, 719 for S. vehense, 408 for S. squamosum and only 138for S. sirbanun and 101 for S. damnosum s.s. t'Cro8s" trensmissions have shown thet: - S. soubrense/S. sanctipauli, forest species, transmit very weI1, in their originalbiotope, the savanna parasites: the nunber of infective lervee is higher then that recorded in S. damnosum/S. sirbanun, which are netural vectors of those parasites. - S. vahense and S. squanosum (Ivory Coest populations) species living on small riversin the forestr ere poor transmitters of the paresites essociated with the large forest rivers andsti11worsetransmittersofthe''savannaspecies'.of@, - S. damnosum s.s. end S. sirbanun give only a very low parasite yield when they torge themselves on onchocerciasis patients infected neer forest rivers (102, 123). 5.2.5.2 Role of different species in natural conditions In natural conditions the vector role of a blackfly population in the transmission of o. volvulus depends not only on its intrinsic vector cepecity and the origin of the parasite, but also: - on the meen longevity of the flies and in particular of those which are infected presence of too many paresites cen shorten the vector's life; the - on the amount of contect with the paresite reservoir, which is governed by the anthropophilia of the vectors end the percentage of parasite carriers in the human population; - on the dispersion of the fIies, which can lead to dissipation of the parasite reservoi r . In the sevenne the percentege of perous females of the S. darnnosurn/S. sirbanum pair carrying infective larvae averetes 2.54 but may be as high es 8.5a in hyperendenric foci where nen-bleckfly contact is very c1ose. There is great consistency in the results frorn Hali to Benin. The parasite loed is in about two larvae per infected female (1O2,123,2261. The S. soubrense/S. senctipeuli pair is intrinsically the rnost efficient vector of the S. dannosum complex in tJest Africa. In natural conditions the number of L 3 Onchocerca lervae per infected female rentes fron two to eight. The proportion of infective perous females in S. sanctipauli populetions in the forest is 0.254 in the Ivory Coast (L23,233) and 2.91 in Liberia (59). The percentage of infective parous females of S. soubrense in the Ivory Coast declines a8 one approaches the northern linit of its erea of distribution, falling from 2.11 in the forest to 0.54a in the country's northern savanna part. Similarly, the enthropophily of thet species diminishes es one proceeds northwards (232,233\. In Togo and Benin, under savanna-type conditions, the proportion of infective parous femeles reaches almost 4A (226\. The role of S. soubrense/S. sanctipauli in the trensmission of severe forms of onchocerciasis hes been discussed above (see section 3.2). S. vahense has hitherto been essociated with benign forms of onchocerciesis even when the transnrission rate is high. fn the Ivory Coest forest the proportion of infective Perolrs femeles of this species is as high es 101, and the load eight larvae per parasitized fenale. In the Ivory Coast savanns, on the other hand, this species is scarcely infective at r11 (123). ocP/84.3 Pege 87 It would be rash at present to associete S. squarnosurn with one perticular forrn of onchocerciasis, for this speciflc nane probably brackets together severel taxons ofb1.eckfly. llherees in the Ivory Coast forest S. squamosum is found in foci of reletively rnild onchocerciasis, in the Ghana, Togo end Benin sevennas, it is on the contrary very ebundant in reg,ions where onchocerciasis is considered as severe. The percentage of infectiy6 perous fenrles in thoee erees is 5a and each of theru herbours on everaBe 1.4 infective lervae(L 3) (61, 46). A considerable body of date has been collected on onchocerciesis transmission, but theirinterpretation in terns of epideniology is often difficult. llany ambiguities must renrin unresolved until the parasites transported by the verious species can be identified ryith certainty. 5.3 Develoment of new lervicides end nes bleckflv control methods 5.3.1 Historv and objectives Cootrol of blackflies has hitherto been based on destruction of the larvee. At firet DDT wrs used (08, 64, 219) and then, when it sas benned for ecologicel reesons, methorychlorin tforth America (73) and tenephos in Africe end Centrel America (151, 219). Adulticides heve beea used only for pieceneel operetions whose effectiveness is inpossible to evalur,te (152, 166). It has been found thet certain nodifications of the environnent, notably the constructioa of dene, reduced blackfly populations, but no large-scele specific ecologicrl coatrol operrtion has been carried out to date or seens feasible ia the nediun tero, end the nain concern is to ensure thet development works heve no adverse effects on health (104). In tbe Prograrrnrers reseerch effort, priority has therefore been given to the developnent of new larvicides. Studies in this field had started long before the Leunching of OCP ln the leboratories of the region, particularly et the fRTO in Boueke. They were continued rith the Progrrme's support end then erpended es fron 19E0 with the advent of resistance to orgenophosphates; a reseerch team speciallzing in the development of ner insecticldes s.8,ia addition, set up ia the Vector Control Unit of OCp. Reseerch hrs elso been conducted on control by adulticiding end on non-chenicel control technigues. 5.3.2 Performuces erpected fron larvicides The ideel larvicide fornuletion should (67. 26512 - produce 10Of mortrlity in blackflies at a dosage of O.1 ng/litre/l0 nn; - have los n.malian toricity (LD 50 > 1000 mglkglrat); - do little danege to the environnent, end ia perticular ki11 neither mlcrocrustece.ns nor fish at the effective dosege; - enulsify spontaneously and be steble in tropical climates. The effectiveness of an insecticide depends on: itg intrinsic activity, which can very with tenperature; - the guantity of active preparetion that reeches the target insect; for blackflies, this is the quantity ingested either directly or (as in the cese of Abate) with the suspended particles on which it is adsorbed; - the contrct tine between lervicide end insect. T-tro points ruust be stressed. fn tropicel reg,ions the turbidity of the water crertes fevourable conditions for the use of emulsifiable concentrates, whose active ingredients are edeorbed on to the particulate meterials in suspension in the watercourse, which ere ingested ocP 184.3 Page 88 by the blackfly larvae. Particulate formulations, on the other hand, have to compete with these suspended particles and therefore show little activity in turbid rraters, wtrereas the opposite is the case in the clear rraters of the temperate countries (189, 190). Ttre second remark concerns the contacE time between insecticide and larva. This depends on the duraEion of the passage of the insecticide wave, which ranges from a ferc minutes at the point of application to more than half an hour 10 kE dorrrlstream, and on the transit time of the bolus alimentarius during which the preparation is absorbed. The latter time is very short in S. darunosum (253) and it is therefore not inpossible that some slowly absorbed preparations can pass through the black insecticide trials must be conducted in regions and on the target species. As , West Africa, had been rated inadequate in North America, while the reverge occurred with methoxychlor (73, 190). 5.3.3 The accelerated larvicide developmenE programe Conducted under the joint responsibility of the Vector Biology and Control Division of WIIO (VBC) and the Prograuue, the procedure for development of new larvicides is as follows: flyrs digestive trect unabsorbed. Consequently, the Programne arge\or in ecologically very similar an example, Abate(K/, wtrich has proved excellent in preparations that exhibit an LC5g of less than uito Aedes aegypti and the formulations of nhich have- Phase 1: Selection of technical 0.1 mg/litre for larvae of Ehe mosq low toxicity for marnmals. They are tested to uake sure that there is no cross-resistance to temephos in S. damrosum s.1. - Phase 2: The industry is asked to supply the formulations of the preparaEions short-listed. Ttreir effectiveness is tested in troughs (97, 198) and in minigutters(57). The larvae remain in contect with the insecticide formulation for 10 minutes in running seter. To be rated pronising and short-listed for t.he next phase, preparations must produce 1002 nortality in larvae et a concenEration of active substance of less than 0.5 ng/litrelLO mn and kill neither macrocruataceans nor fish at the dosage effecEive on blackfIy. For preparations based on Bacillus thuringiensis H-14 the minimum level of activity is set at 1.6 rng/litre/I0 m. - Phase 3: River trials. (a) Small-scale trials are intended for measuring the effectiveness and carry of the formulation over a stret.ch of river and evaluating iEs impact on the non-targeE fauna. Its effectiveness is judged by the reduction in the number of larvae on natural or artificial substrates at various distances dorrnstream from the release point. The ttecologicalrr effect is measured by the reduction in the number of organislos on Bubstrates, the increase in drift and the mortality in the fauna placed in gutters anchored in the current (Fig. 10) (155 bis). (b) Full-scale trials must be conducted for a year, or at least a dry 6eason, over the entire area of a basin. Ttreir purpose is to Eeasure the mediurterm effects of repeated applications of the preparation. This is also the tine for solving problems regarding the application and storage of the foroulations. Finally, the effect of the treatments on vector populations and onchocerciasis transmission is evaluated. Ttre results of each series of trials are comunicated Eo the Programe authorities and to VBC, which inform the manufacturers and the Ecological Group. 5.3.4 Results of studies conducted to date (a) organochlorines DDT had been used on a large scale in the 1963-1973 EDF carupaign without causing aqy ecological disaster. A ban was proclaimed on it following obeervations made in temperate countries under very different conditions of use. The various formulations of methoxychlor have proved inadequate in West Africa (67, 166, 198). @P/84.3 Prte E9 (b) organophosphates Temephos in a 2Oa emulsifieble concentrate (Abate C 200) is the preparation enployed by the Prog,rarme since its cotmlencement, at 0.05 mg/litee/LO ru at highreter time end 0.1 ng/litcellO n in the dry seeson. It is sirnple to apply fron eircreft, has e carry of 50 kn et highweter tine, and is tolerable for the environnent. fhe compound and its forrnulation, which were selected after extensive reseerch before the Programte started (204' 2O5,22O,22L,224,225) and ere considered highly satisfactory, have served as the refereace for the development of other preparations. The Protrame is stlll testing new fornulations of teruephos to identify those with the begt cost-effectiveness ratio. Chlorphoxim in emulsifieble concentrate gives perfornanees sirnilar to those of Abate, but it is nore harruful to the non-tar6et faune (2231. Cross-resistances have been denonstrated in ell the orgenophosphorus corupounds tested ercept dichlorvos, which is highly toxic, and ezamethiphos; verious forurulations of this latter preparation ere undergoing river tests (2671. The development of resistance to the or6enophosphetes hes reduced interest in research on conpounds of this cless, which was conducted very actively between 1975 end 1980. (c) The pyrethrinoids Froru this class ere recruited ercellent lervicides thet ere unfortunately very iajurious to the non-target faune. Investigators ere trying, to find the preparatlons wlth the best rotio of effectiveness to sefety in use. Permethrin in 2Of emulsifiable concentrate has given promising results in the dry seesoa, et O.O2 ng/litre/l0 m in Togo. Its irmediate effect on the non-ttrget fauna is 6reater than thet of tenephos, but not enough to rule it out Qlll. fhe fornulations recently given full-scele tests in the Ivory Coast heve not so far dlsplayed satisfactory effectiveaess. NeH synerBized formuletions of deltanethrin ere to be river tested in the light of their good perfornences in the laboretory. OllS 3002 end cyperaethrin are too damaging to the environoent. (d) Preperations of Bacillus thurin:iensis H-14 Becillus thurin:ieusis is an entornopathogenic spore-fonning bacteriun that hes been knosn for over 20 yeers end used in perticular ageinst processionary ceterpillars. The yeer 1977 sew the discovery of the variety israellensis, constituting the serotype H-14 orB.t. H-14 (07, 65), yerlr toxic for nosqulto and blrckfly larvee (66, 156, 250). The ectlvity of the bacterium is due to the secretion of en endotoxin present in the forn of crystels wlth a density of 1.3. This endotorin is in fEct a prototoxin which is deconposed iato torins by the enz3rmes in the digestive tubes of rnosqultos and blackflies functloning in an alkeline nediun (pH 10). These toxins cause lesions in their digestive tracts which kill then within e few hours (250). The product is specific for the larvee of bleckflies, nosquitos and, to a lesser degree, chironomids, which ere the only fanilies of aquatic insect whose di6estive tubes heve a sufficiently alkrline pH for hydrolysis of the prototorin to take place. B.t. H-14 is therefore very safe for the non-target feuna. Ihe bacillus does not reproduce in the natural environrnent and epplicetions nust be repeated exectly as with a chemical insecticide. The epplication of Teknar(R), the formulation at present used in the prograrme, isfraught with nrany constreints which limit the use of the preperetion (see section 1.5.1) Hence the development of operational formuletions of B.t. H-14 has become one of the Prograrme' s priorities. ocP/84.3 Pate 90 The collaboratlng leboretory of the IRTO hes tested a very large number of preparetions supplied by the industry. Appreclable inprovements heve been recorded in the experirnental formulations. There is an ernpirical side to this reseerch, for sone of the many physical endbiological peraneters are insufficiently known. Erperinentation must therefore be stepped up rnd ertended to a very eerly stage in the manufacture of the product. (e) Other conpounds Grorth inhibitors have not hitherto given encoureging, results, either because they affect only certain stages or because the contact tine necessary for their action is too long to be obtained in running water. New nethods of evaluation ere being, developed (2641. The carbanates heve shown little promise and are difficult to fotmulete in emulsifiable concentrates. Erploratioa of new classes of pesticide such as the avernectins and the sulfites is in Protress. 5.3.5 Foruulations of lervicides The formulation plays a key role ia deter,nining the effectiveness of the carry of a larvicide and its eese of appllcation. In some cases it deter.nines the specificity of a nolecule vis-l-vis certaln troups of insects since lt presents that nolecule in a form shich only certain groups ere eapable of absorbing, (e.9. prrticulate fornuletions or nricrocapsules) Eruulsifieble concentrates (ECs) heve proved the best vehicles for the chemical larvicides used hitherto. In the case of Abete, the ective preporetion is edsorbed on to the clay particles carried elong, by the river and ingested by the lrrvae. The density of BCs nust be between 0.95 and 0.98 for them to remein in the upper levels of the river where blackfly larvae live. Tiny variations in the ingredients end the fotmulation ceu result in conslderable differences in effectiveness and especially in cerry: thus 208 ECs of Abate purportedly identicel but coning, fron different firms have shown dlfferences in carry of up to lOOf. Full-scele eveluationg must therefore be mede of aLl formulations designed to be used operationally (67, 190), and there must even be a system for continuous testing, of betches received. Slow-release briquettes of ternephos heve been tried with success in Guatenala but their use remeins confined to very snell watercourses (151). Particulate and colloidel formulations are not very effective in oCP conditions (2231. Uater-dispersible concentrates are the vehicles of B..!. H-14 in Teknar, the ective ingredient being present in the forn of one-micron particles. This hes proved far more active than particulate foroulations of B.t. H-14 in which the particles range from 5 to 15 microns in gize and thus carne into competition with the substances in suspension in the river water (69, 189). Digestible nicrocapsules of Reldan(B) (chlorpyrifos-nethyl) or slow releese nicrocepsules of Actellic(B) fpirinlphos-methyl) had given good erperinental results buL these could not be reproduced with the industriel batches (1E8). Dlgestible nicrocapsules which liberate the active preperetlon only in the insect's stomach are under consideration as foruulations for the pyrethrinoids so es to reduce their toriclty for the non-terget fauna. But the techniques of manufacture of nicrocapsules do not seem to have been conpletely mrstered. 5 .3.6 Adulticiding It was noted that treatnent by helicopter of forest galleries with deltamethrin to control tsetse flies caused a very merked reduction in blackfly populations (32). In the 1i6ht of this finding,, consideration hes been given to edulticide treatnents to destroy reinvading blackflies, preferebly before they have had tine to transmit to the population the infective larvae they are cerrying. tJere this strategy to give good results, it would be worth considering for the protection of igoleted sites. ocP/84.3 Pste 91 The basis for sucb control by adulticiding is treetment of a fairly considerable part of the forest galleries near the blackfly oviposition sites. It has been proved that reinvading fenales lay before biting and they are believed to rest on the vegetetion eround those leying, places. It is not, however, known what proportion of then rest in this way, before or efter oviposition. Furthermore, the data so fer obtained on the bleckfly resting places show that they are widely disseminated throughout the galleries (13). ff these findings are confinned, the size of the arees to be treated would limit the possibilities of using this strategy as an alternetive to lerval control. No judgenent can yet be pronounced on the role it night play io the future strategy of the Programre. To evaluate the potentialities of control by edulticiding, OCP has cerried ouL erperimental applications of perrnethrin from the ground on the tl6 bosin in Togo whlch were inconclus ive. 5.3.7 Ecologicel control nethods Blackfly control takes adventa6e of certEin civil engineerin6 works, such es dans which elininate the breeding, sites in the lakes they forn (104); it would not, however, suffice on its om to justify such costly underteking,s. At the 1983 session of the Erpert Advisory Comittee (2731 it was proposed thet channels be dug to bypess stretches of repids provided such large-scale operetions were conpatible with the countries'overall developnent plans. lluch has been written about renoving rock shelves to elirninate bleckfly habitets, but nothing of the kind has been undertaken so far. There have, on the otber hand, been neny instances where developnent uorks heve creeted highly productive breeding places: dam spillways, irriEation canals, bridge piers, artificiel fords, etc. Since their effects cannot be elinrineted they nust be rnininized. The alternate operation of the turbines et Se1ingu6, tfeli, and the rationel utilization of the sluices of earth dens are eranples of sound manegement of such constructions uith an eye to blackfly cootrol. Elinination of ruins of artificiel fords end bridges is recoruuended ( 104, 194, 261 ) . 5.3.8 Other control nethods Aa evaluation must be made to deterrnine shether treps (eluniniun pletes), by capturing reinvading females when they cone to lay before biting, can significantly reduce the nurnber of infective larvae introduced by then. Individuel prophylaris by wearing protective clothing is burdensome for workers in the field, who are the most exposed. Ointnent containing repellents gives only brief protection shose renewal becomes prohibitively erpensive. A research effort is being directed towrrds local products and small trials will be conducted with peln oi1 in Togo (212). The prospects held out by biologicel control using, nernithids (211) end Bacillus sphericus are not encouraging. Genetic control is not a practical proposition in the present state of our knouledge. 5.3.9 Developrnent of control methods end future of oCP The development of new insecticides is aimed at two objectives: - having less expensive and more effective preparetions evailable then those at present in use; - having substitute preparations or control methods available in case of development of resistance to orgenophosphetes. The conclusions drarn in Chapter II ebout the need for neu preparations end the budg,etary consequences of their use are also relevent here. At present, the Protrentrle hes at its disposel: - two highly operational organophosphorus preparations, Abete and chlorphorin, shose use ig restricted to S. dasrnosun s.1. populetions susceptible to organophosphetes; ocP/84.3 P8te 92 - e formulation of B.t. H-14, Tetnar, used meinly in Iow-weter conditions presents serious difficulties. Research to develop improved formulations actively pursued. end whose use is being, The research being conducted in phase III concerns en organophosphorus compound, azanethiphos, end two pyrethroids, permethrin and synergized deltanrethrin. The research in phase II concerns growth regulators (IGRs) and a number of pyrethroids. Control by adulticiding is only beginnin6 to be tried out. 5.4 Reserrch on the parasite This hes been focused on the texonony of the parasite, its biology and its detection in lDen. 5.4.1 feronomv of perasites the objectives of and justifications for reseerch on the taxonomy of the parasite onchocerca volvulus are explained in Chepter III.2 above. It is possible by nrorpholog,ical ereminetion to differentiate the adult worns and nicrofilariee of o. volvulus frorn the species of the sarne Benus thet have en effinity for bovines, in particular o. ochens,i (35), but this is of linited interest since these forns develop in different vertebrate hosts. It has not proved possible to distinguish between o. volvulus specinens of different geogrephical orig,ins. Furthermore, the L 3 larvae of O. volvulus and O. ochenri, which develop in the sa.ne speeies of the S. darnnosum compler, renain morphologically indistinguishable; this prevents correct evaluation of ATPs in re6ions where S. dannosun s.1. exhibits a substantiel degree of zoophilie (146). Chromosone studies, applied with success to verious nenatodes, including the ascerids, heve not yet been underteken on filariae. By electrophoresis of the isoenz3rmes of adult wortns it proved possible only to differentiate between O. volvulus end related species (55). Only one enzlrme system (LDH) out of the seven tested showed sltght differences between O. volvulus populations. llore recent studies have shown differences between the isoenzyrmes of two populations of worms, but the genetic distance between these populations is ninimel (77). Histochemicel study of the acid phosphatases of skin rnicrofilariee has demonstreted consistent differences between populations of savenna and forest perasites in 20tf of the nicrofilariae (119, 215). The sene nethod applied to L 3 lervae has shorn that a certein nurnber of those collected fron S. damnosum s,L. were not Onchocerce volvulus (96). In the research at present being conducted for the identification of parasites, use is also being rnade of irmunological techniques, DNA enelysis and mass spectogrephy. 5 .4.2 Biolpcf qf paras i tes (a) Longevity of the different stages in nen The latent phese of the parasite, i.e.the time elapsing between the penetrabion of the infective larvae (L 3) into the humen orgenism and the appearance of rnicrofilariee in the skin, has been estinated at from one to three years (2O,42, 110). In the Protramne area, preliminary estimates put the longevity of fenrale wor.us at between 8 and 12 yeers, which tellies with the epidenriological observations (77,133). The longevity of microfilariae is perhaps more than three yeers (135, 14O). (b) Structure of adult worm populations Study of the structure of edult worn populations hes been nade possible by the technique of dig,estion of the nodules by collagenese, which liberates the worms without demaging them (142). ocPl84.3 pate 93 In untreeted regions, the female womr populations observed contained 3a of juvenlles. 70* of sexually active specinens, 1O to 2OA of worms with ernpty uteri that were in a diapr,use phase or "menopausel", end 101 of dead fenrales, In regions that have been under control for seven there is no input of yount worms. There ere of course 454 of inactive end 377 of dead femeles. Furthermore, dinrinishes, for the deed worms are disintegrated after Horms (77, 143). (c) Fertility of worns years, populations ere older since no Juveniles and there nay be up to the averege nunber of worms per nodule e while and are not repleced by aew Eech female emits from 500 000 to one nillion microfileriee per year; these enissions fel1 into three periods alternatin6 with diapauses (77). neles (d) Sperniogenesis, not yet rruch studied, apperently ceases before the death of the(144). l{ovements of adult worms The juvenile worms produce nodules or make their wey into pre-eristint ones. The neles can move from one nodule to another, 5 .4.3 Imrunolo:ical diaanos is Pcresitological die6,nosis is insufficiently sensitive in ceses with lor worar loeds. However, in the terminel phases of oCP these will be the nain types of cese persisting. Hence the development of a sensitive, speciflc end sinple inmunologicel diagnostic nethod would be highly desirable fron the viewpoint of the long-ter.n stretegy. In trying to detect antibodies the difficulty hes to be faced of obtaining yery pure antigens giving specific reactions (01). Investigetors heve tried to use as antig,ens products of the metabolisn of adult O. volvulus kept artificielly alive; in prelirninary tests e specificity of 95a has epperently been obtained by using the ELISA technique, but these results will need to be confir.ned. Demonstration of circuleting entigens by rnonoclonal antibodies is a pronisiug dlegnostic nethod which is at present being investi6ated in various laboratories. 5.5 Research on chenotherapv of onchocerciasis 5.5.1 Objectives and orqanization of reseerch on chemotherepv The control of onchocerciesis was besed, in tlest Africa, on the destructioa of the vector because there wes no elternetive end, in particuler, no drug utilizable in mass canprigns or by those delivering prinary heelth care. The PAG mission wes fully auare of this deficiency and its conseguences, particularlyfor the concluding phases of the Protrsme. The Pro6rarnners advisory bodies, from their very eerliest sessions, recomnended that vigorous ection be takea by HHO for the developnent of ective and easily edministered filericides. Thus chemotherapy of onchocerciasis becrne one of the major objectives of the Fileriasis section of the TDR Protrame. starting, in 1982, speciel funds were set eside by the Protrgryne for an onchocerciesis chenotherapy project (OCf) to be conducted under the scientific responsibility of theDirector of the UIIDP/tIorld Bank/lJllo Special ProBreme for research in Tropical Diseeses (TDB) and the adninistrative responsibility of the Director of the Prograrme. ocT has its own steering conmittee. In the seerch for new drugs, priority was given to mecrofilaricides since they alone coul.d make possible elinination of the perasite. But microfilaricides and prophylactic egents were elso taken into consideration. Action has been undertaken elong two 1ines: - re-evaluetion of the existing filaricides diethylcarbarnazine (DEC) and suramin (191, 192). ocP/84.3 Pste 94 - developrnent of new filarlcides. The "candidates" were chosen from among, drugs usedfor other PurPoses, such as the enthelminthics, with or without nrodification of their fornulee, and among the preparetions synthesized by the industry or in reseerch leboratories. 5.5.2 Re-evaluation of filericides 5.5.2.1 Diethvlcerberuazine (DEC) DEC is r nicrofilaricide that reduces the parasite load without, however, elininatingit. The verious treatnent schedules are based on administration of repeeted doees for at least a week and generally longer. DEC treatnent produces a nunber of edverse side effects known collectively as the Itazzotti reaction. It can also produce harrnful effects on the fundus oculi in petients with ocular parasltes (123). Administretion of the preparetion in gradueted doses or in rssociatioa with corticoids or antihistanines does not completely eliminete the l{azzotti reection (prurltis, fever, dermatitis End ocular inflanuretion), which ls ertremely dlsagreeable for petlents (02, 138, 149). Association of DEC rith levamisole has not inproved the tolerebility of the preparation; addition of prednisone has ettenueted the Hezzotti reaction (03, 23, 107) Associatlon of lodoxamide rith DEC has proved effective, in do6,s parasitized by Dirofilaria imritis, for preventing the eide-effects. ft is going to be tested in men 5.5.2.2 Suraurin Treatnents at low dosages spread over sir weeks (4 g of preparation per adult petient) have produced micro- and mecrofilaricide effects. Despite the precautions taken, the eide-effects have not been negligible and some patients have hed to stop teking the drug. Surunin treatment is therefore reserved for speciel ceses or situations and must be given under medical supervision (140, 141, 168). 5.5.3 Develoonent of new filericides 5.5.3.1 Procedure for screeninr of preparations The procedure established by TDR conprises an initiel phese of experimentetion in vitro or on animel models, after which pronising preparetions are tested in nen with due regard to llHOr 8 ethicel ruLes. Erperinentetion in vitro and on animals Stage 1 Stage 2 Stage 3 Stege 1 Stage 2 in vitro on L 4 lervee of Brusia pahen:i on fileriae of rodents on Dipetalonema viteee in l{astomvs or other rodents on onchocerce eibsoni in bovines (24). Preliminary tests for toxicity, teratogenicity and carcinogenicity Tests on healbhy subjects A. Tests on subjects with low-leve1 infections B. Tests on heavily infected subjects, in hospital Teste on man ocP/84.3 Psge 95 I state 3 - Hass field trials. No preparetion has reached this stage. 5 .5.3.2 Perfor.nences of the verlqus compounds tested l{etrifonate is e rnicrofilaricide less active than DEC and with the same disadvantages(o2, 4L, 56, 76, 16E). l{ebendazole interferes with enbryogenesis in onchocerea (75, 76). It has given unconvincing results and, moreover, proved teretogenic (04, gg), Flubendazole is e long-lasting embryostatic which nust be adninistered parenterally. The injection is painful and causes abscesses; preperations easier to adrninister are uLin6 sought (04). on its orn, Levamisole is ineffective; mixed with DEC or mebendezole, it hes displayed no appreciable advantege (04, 74, 88, 107, 231). llelarsonyl potassiun is an ective but toxic rnecrofilericide thet ceuses arsenical encephalopathies (39), A neu conpound ProPosed by Ciba-Geigy has proved en effective mecrofilericide on o- gibsoni. Trials in man are to be underteken as soon es they are authorized by the ethical comittee. Ivernectin is eo "outsider" which hes not tone through TDR's screenint process but hasbeea tested in Senegel end France before being, taken up in the UHO circuit fOS, ZOl. It is a nicrofilaricide which acts in a sing,le dose without epperently ceusing any significantl{ezzotti reection or enJr eggravetion of eye disorders even sheo the dosege is as hig,h as 200 nicrogramres/kilo end the parasite load is high (200 nricrofilariae per skin snill. Itproduces a 904 reduction in ruicrofiLariee shich apparently persists for three months according to tests perforrred at the Chernotherapy reseerch centre in Tanele, Ghena. Finally,it hes displayed a prophylactic effect ageinst o. ribsoni in cattle. These are of coursepreliminery trials. 5.5.4 The outlook chemotherapv An effective end easily adrninistered drug would be ertremely desirable for tackling theterruinel pheses of the ProBramte. Its distribution could be organized through the horiiontalperipheral public heelth structures shich will have a role to play in the devolution of thePrograme's activities to the Stetes. A nacrofilaricide would eneble the elirnination of residual pockets which necessitateprolongation of vector control; it could also be used in snall, isolated foci. Aprophylactic agent would enable reinvaded zones to be protected. A rnicrofilaricide, bydininishing the reservoir of paresites, would help to reduce trensmission, but sould not seemto offer as nany advantages es the forrner two types of drug. ocP/84.3 PsBe 96 CHAPTER VI TR,f,INIIIG OF PERSO}INEL Control of onchocerciasis would have been inconceivable without a training conponent which was provided for in the PAG report (245) (Annex V.6). The idea then was mainly to train the senior and interrnediate steff for the Protrarune, recruiting then in the participating States, The Scientific end Technical Advisory Conunittee, et its fourth session in L976 (247\ stressed the need to train personnel not only for the requirements of OCP but in order to cre.te a body of highly guelified professionals covering all aspects of onchocerciasis in the participating Stetes and other countries where the disease res rife. It coneidered, too,[t"t po.t,r should be established in the netional organizations to ensure ProPer ctreers for those professionals, especially if they were not physicians. The establishnent of a long,-tern strategy in which devolution pleys a key role gives added strength to these viess end would confirm, sere it necessary' the need for training national staff. A detailed account of the Progra.me's tra1nin6, activities was Presented to the Decenber 1982 session of the Joint ProBrernne Comrittee at Banako (255). An updated suurary is given in the table appended hereto. Study grants are provided at the request of the States. OCP selects candidates in consideration of their past cereers and the functions they are to be assigned to. Since 1983 candidates have been working with the Progremne for e month during which their suitability for specialized treining is essessed. 6.1 Level of training It was decided in 1983 that training should be et two levels, for senior staff and technicians, but with different rnodules depending on the attainnents of the cendidates. (a) Senior steff ttedicel personnel have been able to take specialized university courses of one to three years' duration in perasitology, ophthalmology, epiderniology and public health. In addition, supplementary post-university courses of 3 to 12 months'duration have been available for cendidates with the requisite basic training. Finally, to conplete the ranBe of training ectivities, refresher or initiation courses heve been given, usually within the ProEremne. Non-medical personnel (nrainly entornologists, hydrobiologists and econonists) heve taken curricula leading to nester's degrees and then to "Diplome d'Etudes approfondies"(French-lanBuage system) or to a llaster of Science degree (English-lantuage systen); some cendidates have had the opportunity to defend theses. This instruction has been regulerly supplemented by field training periods in the Progratme erea. For sotne specialists who were already qualified training has been limited to a supplementary post-university period. (b) Technicians Courses of four to sir months' duration, totether with refresher training, heve been org,anized for technicians, generally within the OCP area. (c) other categories of Personnel Administrative or technicel officers have had refresher training geared to the requirements of the Progrerune. English or French language courses have been provided for staff needing to be bilingual. 6.2 Discip lines Teble 8 shows that the major part of the trainin6 activities has concerned entomology. Thig is due, firstly, to the fect that the Progranrte's strategy hes been based on vector control, which is its mein weepon and, secondly, to the shortage of entonologists when the Prograone started. , ocP/84.3 Pste 97 For monitoring the equetic environment hydrobiologists have had to be trained from scratch or given supptementary courses. For ell physicians end nurses elready possessing basic knorledge or even sound practical erperience in parasitology, training has usually been limited to supplementary post-r:niversity training or refresher courses. Four specielists in ophthelnrology heve been trained and two heve had refresher training. have beenStudy grents for treining in public health, epiderniology end heelth economics made available since 1980. The shere ellotted to the various disciplines anont the grants distributed is reviewed eech year in the light of the strategy and of the needs and requests of States. Thus in 1983 OCP decided to offer grents in new disciplines in order to help States ensure hermonious socioeconomic development of the onchocerciesis controlled ereas, Farm nanag,ement, conservation of the environment, forestry techniques, stock-reising, sociology and statistics feature in the list of study grents proposed by the Progranune. 6.3 Treininr locations It is of course Universities which have given training of university type, end most of it has been outside Uest Africe. Nevertheless, the university of Daker hes treined an ophthalnologist; the university of Abidjen has just set up et Bouak6 a centre for training in nedicel end veterinary entonolog,y, which uill serve the whole region and is supported by UHO; and the Institute of Public Health in Benin has also teken students. This transfer of treining activities to the region concerned is in keeping with the logic of the Protrsflrre. llost of the supplementary and refresher training of senior stEff as well es the training of technicians hes taken plece in or near the ProBrsr@e area, in regional institutions such as IRTO end IOTA or national ones such as the universities of Abidjan and Legon, Accr8. The Programe structures heve also proved highly effective for sone kinds of specialized training 6.4 Conclusion To dete the Progranure has provided training for 133 persons: 16 fron Benin, 10 fron the Ivory Coast, 2 fron Guinea-Bissau, 13 frorn Guinee, 17 from Ghana, 27 from Burkine Faso, 12 fron lleli, 6 from Nig,er, 1 fron Nigeria, 1 fron Sierre Leone, 3 from Senegel, 1 fron Suden, 18 fron Togo, 3 fron the United Republic of Tanzenia, 1 from Uganda and 3 frorn the IIHO Regional Office. The Progralure has also lived up to the expectetions of its promoters by not only training, a considerable number of specielists in onchocerciasis for uest Africe, but also stinuleting the interest of participating States in certain disciplines hitherto considered as minor ones. tJithin its orn organization, it hes developed the concept of interdisciplinerity which is reflected in the veriety of its treining streams. This is a sine que non for any inte6ration of ectivities. The inmrinence of devolution should be an encouraBenent to press on with such ection, rhich aII the perticipating countries consider as of priority inportence. Already nov I najority of the senior Progremle staff ere nationels of the participating Stetes or of neighbouring countries and most have been treined by or sith the support of the Prograrune. ocP I 84 .3 Page 98 TABLE 8. TRAINING ACTIVITIES CARRIED OUT OR SUPPORTED BY OCP BET}IEEN 1975 AND 1983 Entonology Hydrob iology Parasitology and epidemiology Ophthe lmology Economic sc iences Miscellaneous Long-durat ion University level 2 to 3 years BN IC GH BF TG GH2 cH 1 ep. GH I par BF 2 par BN GH TG t 2 1 BN IC GH BF ML SN 1 l 2 1 I I Pub. health BFl Gen. med NGT T=26 Supplementary spec ialized post-universiEy traininB 3 Eo 12 months GC ML NG TNI BN IC BF 2 I I GH GC T.iHO GC NG T I Pub. health BNl Pestrcides anaI. cHl T = 16 Trainrng of technicians 4 to 6 months BN7 IC7 GHl BF8 t4L 1 NG3 TG 14 cc5 GB2 TN2 sN2 UG1 GH GC HV i 2 I GC1 BF1 T=65 Refresher or initiation course, up to 6 months Senior staff Technicians ML NR SL SU BN GC BF ML TG wHo t,IHo BF I 2 T= 14 BN GH I 4 MLI BF4 BF3 80 14 18 10 7 r=ll1 BN= BF= GB= GC= GIt = IC= ML= Ben in Bourkina Faso Gu inea-Bis sau Guinea Conakry Ghana Ivory Coast MaI i NG= NR= SL= SN= SU= TG= TN= UG= Niger N iger ia Sierra Leone Senegal Sudan Togo Tanzania Uganda 2 I I 2 I 2 I I I t 1 1 ocP/84.3 p.Ee 99 FrG. 20 DIAGRAM OF MULTIPLE-GUTTER APPARATUS System for individual setting of each gutter allowing Yertical and latcral adjustmcnt 4 1 Battery of gufters (experimental part) in which the natural substrates are placed2 Support system allowing vertical adjustment of entire structure3 Stop screen for natural drift with current accelerating device4 Pesticide solution containem5 Collectors6 Nets for collection of drift of organism from gutters wHo slrilrl ocP f s4 .3 Page lOO BIBLIOGRAPHY Articles parus dans des ouvrages ou revues scientifiques Aobroise-Thomae, p. (1975) Etude critique des proc6d6s diagnostiques parasitologiques et innunologiques des fitariosee humaines in Diagnosis of Parasitic Diseases, Prince Leopold Inet., Antwerpen ed.' 119-124 Awadzi, K. & Gillea, H. M. (1980) The chenotherapy of onchocerciesls. III. A coryarative study of DEC and oetrifonate. Ann. troP. Med. Parasit', f!, 199-210 A 1 2 3 4 5 Awadzi, K., Onre, L. LtE., Berckenridge, A. M. & Gilles, H. M. (1982) The onchocerciasis. IV. The effect of prednisone onthe Mazzotttreaction. chemotherapy of Ann. troP. R. Acad. Sc. Paris (DiPtera, Cahiers ORSTOM Med. Paragit. 75,547-555 Awadzi, K., Schulz-Y,ey, H., Howells, R.8., Haddock, D. R. W., & Gilles, H. M. (1982) The chemotherapy of onchocerciasis. VIII. Levamisole and its combination with the benzimidazoles. Ann. t . Med. Parasit 76,459-473 Azitz, M. A., Samba Dia1lo, Diop, I. M., Larivibre, M. & Porta }lauro (1982) Efficacy and tolerance of ivermectin in hrnan onchocerciasis. LanceE, 2, \71-173 6. Ba, O. (1984) Infection load in children born since the control operations in OCP. Abst. Int. Cong. Trop. Med. Mal., Sept ember 1984, Calgary (sous presse) trEs toxique pour les7 8 9 286 p, 797-800 Barnley, G. (1956) Control of Simulium vectors of onchocerciasis in Uganda. Proc. 10th Int. Cons. Ent. , 3 (1958), 535-537 Barjac, H. de (1978) uoustiques: B. Be11ec, C. (1975) Sinuliidae) b s6r. Ent. m6d Une nouvelle vari6ti thurinsiensis var. i r0. 11. 261-275 12. Be1lec, c. a Hdbrard, G. 13. Bellec, C. (1977) Captures dradultes de b traide de piEges drintercePtion, Parasitol., 15 ( 1) , 41-54 Simulium damnosum Theobald 1902 a1 n r:m en Afrrq d'dtude. Cahiers oRSToM ue de lrOuest. s6r. Ent. rn6d. Parasitol. 18 (3) Captures dradultes de . l'aide de plaques d' . Parasitol., 14 (3), 209-217 Simuliidae, en particulier de Sioulium dawrosum les pidges-vitres Cahiers ORSTOM . Ent. n6d. Les lieux de repos des adultes du complexe $!mu!!1rnBellec, C. & H6brard, G. (1980) damnosum. l. Les m6thodes (1980) La drrrdc du cycle des femelles du complexe Simulitm damnosum en zone pr6forestiEre de C6te dtlvoire. Cahiers ORSTOM s6r. Ent. m6d.?;;;il;, t8 (4) , 347-3sB Bel1ec, C. & H6brard, G. (1980) Les lieux de repos des adul damnosum. 2. Etude de la distribution sPatiotemporale. ilEE-I-P.rr"it., 18 (3), 277-289 Bellec, C. & H6brard, G. (1983) Les pr6f6rences en secteur prdforestier de C6te dtlvoire. 2L G) (sous presse) trophiques des vecteurs de l. tonchocercose tes du complexe Cahiers ORSTOM Simul ium ..ilsrrt 14. Cahiers ORSTOM s6r. Ent. m6d. Parasitol., ocP f84.3 Page 101 r5. Bellec, C. & Il€brard, G. Afrique de lrouest. (1983) Fdcondit6 des feurelles du conrp lexe Simulium daunosr.m en Cahiers ORSTOM sdr. Ent. n6d. Parasitol., 21 (4) (sous presse 16. Bellec, C. A xdbrard, G. (1984) Les heures d'activitd de vol des adultes du couplexe Sinulirn damnosum en secteur pr6forestier de C6te dtlvoire. Cahiers ORSTOM ser. Ent. o6d. Parasitol. 22 (sous presse) 17. Bellec, C. & H5brard, G. (1984) D6placement des adultes de Sinuliuo damnosum s.1 autour des gites pr6inaginaux. Cahiers ORSTOM sdr. Ent. n6d. Parasit. 22 (1) (sous prease) rB. Bellec, C., zerbo, G., Nion, J., H'ebrard, G. & Agoua, H. (1984) Utilisation exp6rimentale des plaques dralr-minirm pour lr6valuation entomologique du Prograunne de Lutte contre lronchocercose dans 1a r6gion Parasitol., !l (sous presse) du bassin de la Volta. Cahiers ORSTOM s6r. Ent. m6d. ('1983) Reinfestatione of the south-eaarern flank of the rol Programnre by wind born vectors. Philosoph. Trans. R. Soc. 19. Carlcon, D. A. & IJalsh, J. F. (1981) Identification of tt o West African Balckflies(Diptera Sinuliidae) of the Simulium damrosum species complex by analysis of cuticular paraffins . Acta tropica, 38, 235-239 20. Chartres, J. C. (1955) onchocerciasis. Incubation period, clinical course and treatnent at first aid. West Afr. Med. J. 4, t30-134 21. Cheke, R. A. & Garms, R. Onchocerciasie Cont London (in preas) 22. Cheke, R. A. & Harria, J. R. w. (1980) Seasonal rize variation in fe,nales of thcSinuliro dauroguo corylex in the Ivory Coaer. Tropenred. Paraait., ]!, 117-120 & Kerner, H. (1982) The fecundity of Simulitm damroeum in23. Cheke, R. A., Garml, R northern Togo and 56 1 -568 infections with Onchocerca acp. Ann. trop. ll6d. Paraeit. , fg, 24. Copemqn, D. B. (1979) An evaluation of the bovine - O. gibsoni O.gutturosa - oodel as aEertiary Bcreeu for drugs agains t O. volvulus. Tropelungd . Paras it . , 30, 469-474 25 Cooter, R. J. (r983) Srudies on rhe flight perforoance of three cytospecies in the Res., 73, 275-288 of blackflies (Dipt. Sumuliidae). II. Flighr couplex of Simuliuu damnosum Th. 8u11. ent. 25. Coulaud, J. Cenac, 27. Cupp, E. W., Lok, J. B., Bernado, M. J., Brenner, R. J., Zo1lack,(1981) Couplete generation rearing of Simuliun damnosum s.1. 28. P., LariviEre, M., Gervais, M. C., Gaxotte, Ph., Aziz, A., Delnol, A. M. &J. (1983) Traitement de lronchocercose humaine par lrivermectine. BuI1. Soc Path. exot., 76, 581-688 Tropenmed. Parasit., 32, 119-122 Dadzie, Y., Rol1and, A. & Thylefors, B. (1984) The evolution of ocular onchocerciasis in the Volta River Basin over the period of five years of vector control. Tropenmed. Parasit., 35 (1),41-45 29. Dadzie, Y. et al., (1984) Ocular onchocerciasis in OCp Int. Cong. Trop. Med. Mal , September 1984,Ca1gary R. J. & Scoles, G. A in the laboratory. areas under vector control. Abst.(sous presse) 30. Davies, J. B., Crosskey, R. W., Johnston, M. R. L. & Crosskey, M. E. (1962) The control of Sinuliurn damnosum at Ab 491-5 10 uja, Northern Nigeria, 1955-50. BulI. Wld. H1th. 0rg., 27, ocP f84 .3 page 102 31. Daviee, J.8., Seketeli, A., [.Ialsh, J. F., Barro, T. & Sawadogo, R. (1981) Studies of biting Sinulirn daunoaua s.1. at a breeding site in the onchocerciasis Control Progro''-'.arLi@dafterinterruPtionofinsecticida1treatuents.EP@ I"rr"it., 32, 17-24 Daviea, J.8., Walsh, J. F., Baldry, D. A. T. & Bellec, C. (1983) The effects of helicop- ter applied adulticides for riverine tsetse control on Sinulium populattons ln llest African Savannah habitat. III. Conclusions: the possible role of adulticiding in onchocerc1aetscontro11n[lestAfrica.@'29'13.l5 . (1979) Euploi des pesticides et pollution des eaux continentales africaines. . Cong. Lutte contre les insectes en miligg gropical, 859-872 DeJoux, C. (1983) Utilisation du t6ndphos en campagne de lutte contre Sinulirm damosr.m en Afrique de lrOuest. Iryact des premiers cycles de traiteuent sur le uilieu aqua- tique . Rev. Hydrobiol. t rop., l5 (2), 165-r8r Denke, A. H. & Bain, O. (1978) Donn6es sur le cycle dr0nchocerca ochengi chez Sinuli]r'a dmroet e.1. au Togo. Ann. Parasit. htm. cory., 53r 757-760 Deeowitz, R.'S. et al. (1982) Inhibition of the adverse reaction to DEC in Dirofilariaimitis infected dogs by lodoxaoide ethyl. An. J. trop. Med. Hyg.,31,309-312 Diakel, J. & Wenk, P. (1975) Aufnatrre von partiklen und insektisiden durch die larvenatadien der Siouliiden. Z. parasit., 50, 189-l90 Duke, B. o. L. (1958) Studies on factors influencing the transmission of onchocerciasis. VI . The infective biting potential of Sinulir.o daurosr-m in different biocliuatic zonca aod its influence on the s potential. Ann. t . Med. Parasit. 62 t64-170 Duke, B. o. L. (1970) The effects of drugs on o. volvulus. 4. Trials of melarsonylpotassirn. Bull. Wld. Hlth. Org., 42, 115F_ Duke, B. o. L. (1970) Quantitative approach of the transuission of onchocerca volvulus.Trans. Roy. Soc. trop. Med. Hvs., 64, 311-312 32 33. 34. 35. 36. 37. J8. 39. 40. 41. 42. 43. Dej ,c .R ux c o Duke, B. O. L. (1974) Further tria forest strains of 0. volvulus I of trichoropone (nretrifonate) against West African . Ann. t Med. Parasit. 68, 241-242 Duke, B. o. L. (1980) observations on onchocerca volvulus in experimentally infected chimpanzees. Tropenmed. parasit.,.ffi- Duke, B. O. L. & Anderson, J. (1972) A comparison of the lesions produced in the corneaof the rabbit eye by ruicrofilariae of the forest and Sudan savanna strains of linical picture. Tropenmed. parasit., 23,Onchocerca volvulus from Careroon. I. The c 354-358 44. Duke, B. O. L., Lewis, D. J. & Moore, p. J. (1960I. Transmission of forest and Sudan savanna Cancroon, by Sinuliun damnosum from various ) Onchocerca Simulir:o coqlexes. st r frou west Africaffi. arrrr.trop. Med. parasitol., 60, 3lg-336 Dunbar, A. I{. (1966) Four sibling species included in Simuliurn damrosrm Theobald from45 46 Uganda. Nature London, 209, 597-599 Dunbar, A- w. & Vajime, C. G. (1981) cytotaxonomy of the Simulir:m damnosum complex.In B1ack flies, Laird ed. Acad. press, 31-44 ocP f84.3 Page 1O3 48 47. Elouard, J. M. (1983) Impact d'un insecticide organophosphord, le t6u6phos, sur les entotroc6noeeg aseocides aux stades prdinag inaux du courplexe Simulium damnostm Theobald. ThEae Doct. Etat, Universit6 Paris XI' 572 pp Elouard, J. M. & Elsen, P. (1977) Variations de lrabsorption des particules alimentaires et de Ia vitesse de transit digestif en fonction de certains paramEtres du nnilieu chez les lanres de Simulium damnosuo. Cahiers ORSTOM s6r. Ent. m6d. Parasit. 15, 29-39 M. & L6v6que, C. (1977) Rythme nycth6meral des ddrivis des insectes et d Hydrobiologie EB ,, -11,poissons dans 179- 183 les riviEres de C6te d'Ivoire. Cahiers ORSTOM, s6r. Elsen, P. (1977) M6thodes drdchantillonnage des populations pr6inaginales de Sinulium daonosum s.1. Th6obald 1903, en Afrique de 1'ouest. I. Distribution vertGffis lffit des nymphes : observations prdlirninairee. Tropenned. Parasit. , 28, 91-96 49. Elouard, J. 50. 51. 52. 53. 54. Eleen, P. (1979) La nature et la taille des particules ing6r6es par les larrres du cooplexe Sinulirn damnosum dans les riviEres de C6te drlvoire. Rev. Zool. afr. 93, 476-484 Eleen, P. (1979) Rythoes circadiens des m6tamorphoses et dur6e de ddveloppeueDt : des 59,etadec pr6i-oaginaux de Siuuliuu danrrosun s.1. Ann. Soc. bel MCd. t 37 1-384 Eloen, P. (1980) contribution I 1'6tude 6cologique des populations pr6imaginales du couplexe Siuuliua daurosum Th6obald 1902 en Afrique de lrOuest. ThEee 3e cycle,uoirercitffi. Elren, P. & H6brard, G. (1977) M6thode d'6chantillonnage des populatione pr6inaginalesde Sioul'iuE daonosuo s.1. Th6obald 1903 enAfrique de lrOuest. II. Obrerivations rurle choix des couleurl, ltdvolution dcs peupleoent! et la r6partition horizontalc autroyen de rubanc de plac tique. enued. Parasit. ', 28 , 47 1-477 55. 55. 57. 58. 59. 50. 61. 62. Flockart, H. (1982) The identification of some onchocerca eep of cettle by itoenzyue analyeie. Tropenoed. paraeit., 33, 5l-5G - Fugleang, H. & Anderson, J. (,l97g) Further observations on the relationship betseen ocular onchocerciasis and the head nodules, and on the possible benefit of nodulectomy. Brit. J. Ophtaluol. , 62, 445-449 Fuglaang, H. & Anderson, J. strains of O. volvulus Garus, R. (1978) Use of morpholog populations in West Africa. Garms, R. (1983) Studie Simulium daurosum Garas, R. & Kerner, M. (1992) The fecund and infections with Onchocerca ssp. (1977) Effects of a single dose of metrifonate on the forestin Cameroon. @ 28, 439-446 ical characters in the study of Sinuliuu damnosuu s.1. T enmed. Parasit. 29, 483-491 s of the transmission of Onchocerca volvulus complex occuring in l,iberffi, ity of Simuliuu damnosum s Ann. trop. Med. parasit. by species of the 70, 101-117 .. in northern Togo &, 561-558 .1 t Garms, R., Cheke, R. A., Vajime, C. G. & Sowah, S. (19g2) The occurrence and movementsof different members of the Simuligq damnosum complex in Togo and Benin.Z. angw. ZooL., 69, 219-236 Garms, R., walsh, J. F. & Davies, J. B. (1979) studies on the reinvasion of theOnchocerciasis Control Progrernme in the Volta River Basin by Simulium damnosum s.1.with emphasis on the south western area. Tropenmed. parasitl ocP f84.3 PaSe 104 63. Garner, A., Duke, B. O. L. & Anderson, J. (1973) A comparison of the lesions produced in the cornea of the rabbit eye by microfilariae of the forest and Sudan-savanna strains of Onchocerca volvulus froo Cameroon. II. The Pathology. Tropenmed. Parasit., !1@ 64. Garnhau, P. C. C. & McMahon, R. (1947) The eradication of Sinulium neavei Roubaud from an onchocerciasis area in Kenya Colony. Bull. ent. Res. 37, 517-627 65. rapid larvicidal Culex univittatus 66. Guillet, P. & Barjac, ll., de (1979) Toxicitd de Bacillus thuringiensis var israelensis Goldberg., L. & Margalit, J. (197?) Bacrerial spores demonstrating activity against Anopheleq gergenti, Uranotaenia unguiculata, Aedes aegypti and Culex pipiens. Mosguito lilelrs, 37, 355-359 pour les larveg de siutrlies vectrices de 1r 289 D, 549-552 onchocercose. C.R. Acad. Sc. Parls 57. Guillet, P. & Escaffre, H. (1979) La recherche de nouvelles formulations d'insecticides utilisables contre les larres des vecteurs dronchocercose en Afrique de lrOuest.c. R. 1 178 Guillet, P., Escaffxe, Il., Ouedraogo, M., Qui11iv6r6, D. (l9gO) r6eistance au t6n6phos dans te complexe siuuliun daurosr.o Es eur la lutte contre les i nsectes en uilieu ical Marseille Dl9, 58 Mise en dvidence drune S. sancti auli etS. eoubrense en C6te drlvoire. Cahi ers ORSTOM s6r. Ent. m6d. Paras t. 18(3), 291-298 69. Guillet, P., Escaffre, H. & Prudehom, J. H. (1982) Lrutilisation drune formulation ibase de Bacillus t,huri is H- 14 dans la lutte contre 1l onchocercose en Afriquede lrOuest. s6r. Ent. n6d. parasit. 20, 175-185 70. Hervouet, J. p. & prost, A. (1979) Organisation de lrespace et 6piddniologie de lroncho- 71. 73. I1r72 cercose. In: Maitrise de lres et d6vel en Afr ue icaleM6mire ORSTOM N 89 1 79-l 89 Eunter' I't. H. (1956) River blindness in Nangodi, Northern Ghana. An hypothesie oncyclical advance and retreat. The Geographical Review, 56, 39g-4i5 is, A. (1982) Peupleuents algaux des rivibres de c6te drrvoire. Rev. Hydrobiol. Trop.,15, 231-239, ibid., 241-251, ibid., 303_312 Jamrback, H. (1973> Recent developoents in control of brackflies. 281-304 Ann. Rev. Ent t8, 74. Jonee, B. R., Anderson, J. & Fuglsang, H. (,|97g) Evaluation of uicrofilaricidal effectin the cornea frou topically applied drugs in ocular onchocerciasis. Brit. J.Ophtalrcl. , 62, 440-444 75. Kare, o. o. (1978) small-scaIe trials of six drugs against o. volvulus.Parasit., 29, 163-167 - Tropenmed. 75. Kale, o. o. (1982) Further trials of mebendazole and metrifonate in the treatEent of onchocerciasis. Bul1. . mond. Sant6 60, 109-1 t3 77. Karahr M., Schulz-Key, H. & Bullini, L. (t984) Recent investigations on O. volvulusin l.Iest Africa. Abst Int. Cong. Trop. Med. Mal Calgary. sept. 1984 (sous presee) Kurtak, D. C., Raybould, J. H. & Vajime, C. (t aingle individuale of Simulium squaoosum 78 Hyg.,75,126 981) Wing tuft colours in the progeny of(rnderlein). Trans. R. Soc. Trop. Med. ocP f84.3 Page 105 79. Bull. mens. A frique 80 Le Berre, R. (1956) Contribrrtion I lrdtude biologique et 6cologigue de Sinuliun damnosuu Th6obald 1903. Dlen. ORSTOM N" 17, Paris' 204 pp. 81. Le Berre, R. (195S) Bilan som-aire pour 1967 de Ia lutte contre Ie vecteur de lroncho- cercose. Mdd. Afr. hoire 15,71-72 82. Le Berre, R., Garms, R., Davis, J. B., Walsh, J. F. & Philippon, B. (1979) Displacenents of Siuuliun and strategy of control against onchocerciasis, Phil. Trans. R. Soc. London B. 287 277-288 Lee, C. W., Parker, J. D., Philippon, B. & Baldry, D. A. T. (1975) A prototype rapid release Bysten for the aerial appl ication of larvicide to control Simrlirln daonosum. PA!{S, 21 , 92-102 Lefelt, J. F. (1976> Aepect clinique, dpid6niologique et psychosocial de lronchocercose en zone de eavane africaine, daus la r6gion de Baoako. ThEse doct. n6d., Marseille L6vique, C., Paugy, D. & Jestin, J. M. (tSA+) Fish Cormtrnities of Ivory Coast Rivers treated by teaephoe. HydrobioloBia (sous presse) Leoia, D. J. (1958) Observations on Sinuliun damnosuo Thdobald at Loko ja in Northern Nigeria. Ann. trop. Ued. Parasit., 52, 216-231 Lock, M. A., llallie, P. M. & Hynee, H. B. N. (1977) Coloidal organic carbon in running waters. Oikos, 29 , l-tl. Lacharrilre, J. Ladreidt de (1935) La maladie du sonrueil en AoF. frangaise, No 1, 736-744 83. 84. 85. 86. 87. 88. 89. 90. Maertens, K. & We D. perstans. ry, M. (1975) Effect of mebendazole levauisole on O. volvulus andand 69, la seneibilit6 s6r. Ent. old. 91 92 93 94 95 96 Trans. Roy. Soc. trop. Med. Hyg., 359-360 Meredith, S. E. O. & Towson, H. (1981) Enzymes for species identification in the Sinulir-rn damrosun couplex frm l.Iest Africa. Tropenmed. Parasit. , 32, 123-129 Meredith, S. E. O., Cheke, R. Simrliuu soubrense and S. & Garms, R. (1984) Variation and distribution of forus of sanct ipaul i in West africa. Ann. trop. Med. Parasit. 77, 527-640 Mokry, J. E. (1980) d:mnosr:o s. 1. A method for estimating the age of field collected fenale Simuliuo Tropenmed. Parasit., 31 , 1 21-127 Mondet, B. (1980) Etudes sur Isomermis lairdi (Nematoda, Mermithidae), parasite de Simulium damnosum s.1. en Afrique de lrOuest. Thlse Doc. 3e cycle, Univ. Paris XI, 16 1 pp. Moreau, J. P., Prost, A., ProdfHon, J. (1978) Essais de nomalisation de la ndthodologie des enqu6tes clinico-parasitologiques sur ltonchocercose en Afrique de ItOuest. M6decine tropicale, 38, 43-51 Mouchet, J., Qu6ldnnec, G., Berl, D., S6chan, Y. & Grebaut, S. (1977) Mdthodologie pour tester ORSTOM, aux insecticides des larves de Sinuliuo daunosum. Cahiers Parasit., 15 , 1, 55-67 Neville, A. C. (1983) Daily cuticular growth layers and the teneral stage in adult insects: a review. J. Insect Physiol. , 29, 2211-2219 Ouar, M. S. & Garrs, R. (1981) Histochemical differenciation of filarial larvae found 259-264in Simuliun daonosrrm s.1 in West Africa. Tropenmed. Parasit,., 32, 97, 9E. 99. loo. 101. LOz 103 104 ocPf 84.3 Page 106 ooar, lrt. s., Denke, M. A. & Raybould, J. N. (1979) Ihe develoPment of onchocerca ochengl to the lnfective stage ln Stmullum danrnosum a'1', wlth a note on the htstochemical rtatntng of the p"tt"lt". Trope-nned' Paraglt' , 39' L57'L62 ooar, M. S., Proat, A. & ttarshall, T. F. de c. (1982) Histochemical enzyme varlatton ln Onchocerca volvulus mlcrofllariae form ratn-forest and audan-gavanna areaa of the onchocerctr"ti-coo-tro1 programe ln Wesr Africa. Bull. WId. H1th. org., 60r 933-934 Pacteur, N. & Georghiou, G. P. (1981) Fllter PaPer test for raptd deter:mlnatlon of phenotypes with hlgh eaterase actlvlty tn organophosphate reslstana mosquttoes' Mosq. News, gt' 18I-183 Paugy,D.(1978)Eco1ogteetbto1og1ed,@desr1viEresdecated.Ivotre. Cahlers ORSTCI{ s6r. Hvdrobiol. , u, 245-275 peteraon, B. V. & Dang, P. T. (1981) l,brphological means of separatlng slbllngs of the Stnulluu damrosum complex Blackflles, M. Lalrd ed., Acad. Press., 45-56 Ptr11tppon,B.(L977)Etudede1atransm1ss1ond.@(Ieuckart,1883)Par Stotrltum daurosuo Theobald 1903, en Afrique tropicale. Trav. D,oc. ORST0M, N' 53, 3O8 pagee Phlllppon, B. (1978) L'onchocercose huuatne en Afrlque de l'Ouest. Inltlatlon ORSTGI, Parte, N' E, 193 pagee Phlllppon, B. & I'louchet, J. (1975) R6percueston des anEnagemente hydrauliques I usage agrlcole sur 1'6pld6u1o1ogte dee naladlea A vecteurs en Afrtque tntertroptcale. Cahlera CENECA. CoIl. Parts. 3-5 oare 1976 , Doc. 3.2-L3, 14 pages 105. Plcg, J. J. & Roux, J. (1973) Faltc nouveaux dans 1'onchocercose. La rnlcrofllanrrle. Sa r6partltlon gEographlque, aes rapports avec les denslt6s mlcrofllartennea cutan6es, 1'albuoinurle et la chlntothdraple. Premters r6sultat8. Ug!-IEgt.:, E, 45L-469 Prod'Ilon, J., Xoreau, J. P. & l.bngtn, C. (1979) Chtmloth6rapie de 1'onchocercoee. Eesal de traltement de masse par la DEC, le l6vamlsole et l'assoclatlon DEC + l6vamlso1e. l.l6d. Trop. (Marsellle), P, 519-628 Prod'Hon, J., Jestln, J. !t., dechan, Y., H6brard, F., ProdrHon, S. M. & quf1ldvdr6, O. (1982) Influence des mlgratlons hunalnes ou vectorielles sur Ia etrat6gie du Progrnme de Lutte contre 1'Onchocercose de la rdgion du bassin de la Volta. Cahlers ORSTO,I, s€r. Ent. m6d. Parasitol., 20, 285-298 1O9. Prost, A. (1977> Sltuatton dans un foyer d'onchocercose du Malt apr0s treize ans de contr6le antislnulidlen. 1. Aspects parasitologlque s. Ann. Soc. belge M6d. trop., 57, 569-575 107 108. 110. Bull. WId. Hlth. OreProst, A. (1980) La latence parasltalre dans 1'onchocercose. 58, 923-925 111. Prost, A. (1980) Le polymorphisme des onchocercoses hurnaines ouest-afrlcalnes. Ann. Parasit. hum. comp. , 55, 239-245 lLz. Prost, A. (1984) Le recensement des c6clt€s dans les Bavanea de la boucle du Nlger. Cahiers ORSTOII. s6r. Sc. humalnes (sous presse) Prost, A., Gorln de Ponsay, E. (1979) Importance Epid6mlologtque du paraslttsme n6onatal par mlcrofllalres d'Onc[ocerca volvulus. Tropenmed. Parasit. , 30 , 477-48L, 113. ocP f84.3 Page 1o7 114. 115. 1t 5. LL7. 118. LzL. L23. L27. Proet, A., Ilerrrouet, J. P. & Thylefors, B' (1979) Les ntveaux d'enddnicltd dane l,onchocercose. 8u11. Org. mond. Sant6, Z, 655-562 Proat, A. & Parls, F. (1983) L'lncldence de la c6clt6 et ses asPects 6pid6mlologtques dang une r6gton rurale d'Afrlque de l'Orest. Bull. Org. mond' Sant6, qlr 491-499 Progt, A., Pre under the Workshop scott, N. & Le Onchocerclasl on Economlc As Berre, R. (1983) The economlcs of bltndness prevention s Control Program in UPPer Volta: a prellmtnarY analYsts. ts of Parasltlc Diseases, Jans sen Res. Found., Belclum, LO-13 Januarv. 1983 Proet, A., Prod'Hon, J. (1973) Le dtagnostic parasLtologique de 1'onchocercose' Revue crttLque des m€thode8 en usage. lEdecine troplcale, S, 519-532 Proet, A., Rougemont, A. & Ba, O. (1980) Mises au Polnt r6centes dpid6mtologlques' blologlques dans 1'onchocercoee. Etudes tr6dlca1es, 3, 65-80 119. Proet, A., Rougemont, A. & Ourar, M. S. (1980) CaractEres 6pld6mlologiques, clLutquea et btologtques des onchocerques de savane et de forGt en Afrlque occldentale. Rernrc crttlque et 616ment8 nouveau:K. Ann. Paraslt. hum. cmp., E, 347-355 120 Prost, A. & Vaugelade, J. (1981) La suroortallt6 des aveuglea en zdre de aavene ouest- afrlcatne. 8u11. Org. mond., Saut6, 59, 773-776 Qu6lennec, G, (1970) Eesale sur le terratn de nouvelles forurlattona d'lneecttctdes, OI'{S 187, fiS 876 et @tS 971, contre les larrreg de slurltee.8u11. W1d. H1th. 0r9., L22. 41, 313-316 Qg6lennec, G. (1971) Obaervatlona rur les d6placementa larvatres dee simrltea en Afrtquc de l'Oreet. Cahters ORSTOIi. s6r. Ent. rn6d. Paraslt.r 2, (3)r 247-254 quflllvdrd, O. (1979) Contrtbutton I 1'6tude des caract6ristlques taxonomiques, blo- 6cologiques et vectrices des membres du complexe Sirmrltuu dauroeum pr6sents en C6te d'Ivolre. lravaux et docunents, @, N" 1O9, 296 pages L24. Qufll{vdrd, D., Gouzy, M., sJchan, Y. & Pendrhez, B. (1976) Etude du comp lexe S. daurosuo en Afrtque de l'Ouest IV. Analyse de l'eau des gttes larvalres en galson sEche. Cahlers ORSTOIi. e6r. Ent. r€d. Parasttol. , L4 (4>, 315-330 L25. QtrtllJvirJ, D., Gouzy, M., S6chan, Y. & PendrLez, B. (Lg77> Etude du complexe S. damrosum en Afrlque de 1'Otrest VI. Analyse de 1'eau des gites larvalres en salson des plules. cahlers oRSTOM. s6r. Ent. m6d. parasltol., 15 (3), 195-205 Qu1116vdr6, D., Gull1et, P. & S6chan, Y. (1981) La r€partltton g6ographlque des espEcee du complexe Slmulium damnosum dans la zone du Projet S6n6gambie. Cahiers ORSTOM. s6r. Ent. ro€d. Paraslt., !2, 303-309 QulllJvdrJ, D. & Pendriez, B. (1975) Etude du complexe Slsrullum darurosum en Afrtque de 1'Otrest II. REpartition 96ographtque des cytotypeg en COte d'Ivolre. Clrh.i.ers ORSTCDi, .s€r. Ent. d. Parasit -t3., (3) , 16s- 172 128 QufflJvJr{ D., Razer, P. & Le piver, M. M. (1976) Erudes du complexe Slm.rllum dg6lssrrm en Afrique de 1'Ourest III. Etude de la morphologie larvalre des cytotypes prEsents en 6te d'Ivolre. Cahiers ORST , L4, 245-258 qurr1JvJrJ,D.&,."n.,,G,,orpho1og1ca11dentif1cat1onoffema1esofthe Sinnrlium damnosum complex ln West Afrlca; dlfferenctatton of S. squamosum and L26 t29. S. yahense. Trans..Rov. Soc. Trop. l.Ied. HvE. , !2, 99-too 130 NP/84.3 Page 108 131. 139. Qull1dvdrd, D., S6chan, Y. & Pendrlez, B. (1977) Etude du complexe Simullum damrosum en Afrlque de 1'Orest. V. Identlflcatlon morphologlque des femelles en C6ted'Ivoire Tropenmed. Parastt., 28, 244-253 irybould, J. N., Davtes, J. B. & l,Iordzifa, E. (L972) A new stmple technlque for reartng 133 Fl progeny from fenalee of Stmultum dauurosuro conplex. II. A modlfted apParatue to protect agatnet power fatlure. Tropenred. Paraslt., 33, 94-96 L32. Rcme, ll. (1984) Trends of epldenlology of onchocerctaels. Abst. Int. Cong. Trop. Med. l'tal Calsarv. eept. 1984 (eous preeee) Roberta, J. M. D., Neuman, E., Gockel, C. W. & Hlghton, R. E. (1967) Onchocerclaste ln Kenya 9, 11 and 18 yerrs after ell.mlnatlon of the vector. 8u11. Wld. Hlth. Ore.r 9, L95-2L2 L34 Bolland, A. (L974) R€sultata de deux examens oculatres pratl.qu6s i slx ans d'lntervalle dans deux vlllagea onchocerqutens de ltaute-Vo1ta. Bull. Org. mond. Sant6, 51, 257 -26L 135. Rolland, A., Proat, A. & Thylefors, B. (1980) Btlan aprEs trois ans du trattement par la suramine d'un vtllage onchocerqulen gous protectlon entomologtque . Rev. lnt. Trachome'Ophtalmo. trop. , L, 9L-97 135. Ro1land, A., Ttrylefora, B. & Palrault, C. (1978) Evolutton sur neuf ans de l'onchocercoee oculatre dans une couunaut6 vlllageotse d'Afrlque occtdentale. 8u11. Org. nond. Segg1|, 55 (5), 8o5-81o L37. Boea, R. Il. & Cratg, D. A. (1980) llechanlsm of flne parttcles capture by larval black fltes. Canad. J. Zoo1., 58, (6), 1186-1192 Rougercnt, A., Boleeon, M.-8., Borges Da Silva, G. & zander, N. (1976) un essal de tratteEent collectlf par la dlEthylcarbarnazlne dans un village d'hyperend6mle onchocerqulenne de la r€glon de Banako. BuII. org. mond. sant6, Z!, 4o3-41o Rougemont, A., Bolseon-Pontal, M.8., Pontal, P. G., Grtdel, F. & sangare, s. (L917) Tuberculln skln tests and BCG vacclnatton ln hyperendemlc area of onchocerctaele. The Lancet, !, 3O9 138 140 Rougemont, A., Hten, M., Thylefors, B., Prost, A. & Rolland, A. (1984) Trattement de 1'onchocercose par la suramlne t falbles doses progresslves dans les collectlvlt6s hyperend6mlques d'Afrlque occldentale. 2. R6sultats clinlques, parasltologlques et ophtalnologlquee en zone de transmlsston contr6l6e. BulI. Org. mond. Sant6, Q(2), 26L-269 141 Rougemont, A., Ttrylefors, B., Ducam, M., Prost, A., Ranque, P. & Delnont, J. (1980) Traltement de 1'onchocercose par Ia suramlne A faibles doses progressives dans les collectivlt6s hyperend6miques d'Afrlque occldentale. l. R6sultats parasltologlques et surieelllance ophtalmologlque en zone de transmlssLon non lnterroopue. Bull. Org. mond. Sant6, 58, 9L7-922 142. Schulz-IGy, Il., Alblez, E. J. & Buttner, D. W. ( 1977) Isolatlon of adult Onchocerca volvulus from nodules. Tropenmed. Paraslt., 28, 428-430 ocPf 84.3 page 109 r 43. 144. 145 . 151. Schulz-Key, [I., Jean, B. & Albiez, E. J. volvulus for the evaluaEion of drug Schulz-key, H. & Klager, (sous presse) (1980) Investigation on female onchocerca trials. T enmed. Parasit. 31, 39-40 Se6han, Y. (1980) Dur6e <ie d6veloppemen t de S. sirbanuo. Vajine et Dunbar, 1975, ir la linite nord de son aire de r6partition en Afrique occidentale. Note prdliuinaire Cahiers ORSTOM e6r. Ent. m6d. Parasit., 18, 59-50 146. Sdchan, Y. (1984) D6veloppeoent dronchocerques animales chez le vecteur de lronchocercose humaine, Sioulirn sirbanrrs. Vajiroe et Dunbar, 1975, en zone subsahdlienne au t{ali, 147 . Afrique de lrouest. Travaux et documents ORSTOM (sous presse) Sinttone, K. R. & Edman, J. D. (1983) Laboratory colonization of the hr.uoan onchocerciasis vector Siruuliuo daurosuo cooplex using an enclosed gravity through rearing systen. J. oed. Ent. , p, 117-126 148. Simone, K. R., Raybould, J. N., Meredith, S. E. O. & Garos, R. (1983) Identification of a laboratory Eating foru of the Siouliuo damrosuo couplex in West Africa. Ann. trop. Med. Parasit. , 77, 523-527 149. Sora, J. & Sona, S. C. I. (1978) Long tero treatnent of children with lolr dosee of diethylcarbr-azine. Ann. trop. Med. parasit. , 27, 79-85 Statzner, B. (t984) Keys to adult and inmqture Hydropsychihae in the Ivory Coast with noter on their taxon@y and distribution. Spixiana, 7(l), Z3-SO Tabaru, Y., Nakanrura, Y., Ochoa, J. O., Molina, p. A. & Takahasi, H. (19g2) preliuinaryfield etudy on lanricide formulations for onchocerciasis vector control in r 50. Guateoala. J . J. eanit. ZooL. 33, 369-377 152. Taufflieb, R. soc. Path (1955) Une caupagne de lutte contre Sinuliuu daurosum au Mayo Kebi. 8u11. exot . ' €, 554-578 1 53. Thylefore, B. 55, 1 15- (1977> vision screening of illiterate popularions. Burl. wld. Hlth. org.,tt9 154. Thylefora,8., Philippon, B. & prost, A. (197g) Transmission potentiale of Onchocerca volvulus and the aseociated intensity of Onchocerciasie in a Sudan savann8 area. T enoed. Paragit. 29, 346-354 155. Thylefors, B. & Rolland, A. treize ans de contr6le (1977) Situation dans un foyer d'onchocercose du Mali aprls antisimulidien. 2. Aspects oculaires. Ann. Soc. belge .t 155 bis. r 56. uCd. trop. , 57, 577-592 Troubat, J.-J. (1981) Dispositif i gouttilres multiples destind i tester in situ latoxiciti des insectic trop., l4(2) , 149-152 ides vis-i-vis des invertdbrds benthiques . n.r.Eobiot. Undeen, A. & Berl, L. (1979) Laboratory studies on the effectiveness of Bacillus ,$uringlen:i9 var israelensis de Barjac against ,sinulium d461ssrrm 1.."... I$q"it"News, 39, 742-745 Vajine, C. c. & Dunbar, R. W. (1975) sub-genus Edwardsellum near and Chromosmal identification of eight species of the including Sinulium damrosuo Theobald (Oipt. ,26, lll-139 t57 . Sinulidae). Tro enmed. Parasit. ocPf 84.3 page 110 158. Vajirne, C. c. & Quillevere, D. (1978) The distribution of the ginYlium daqrogun complex in West Africa with particular reference to the onchocerciasis control Progra^rme area. Tropenmed. Parasit., 29, 473-480 r 59. . Proc. 3rd Sc. lleet. I.C.I.P.E. 23-25 Nov. 1976 160. I{aleh, J. F. (1978) Sticky traps studies on Simulir-m daurosum s.1. in northern Ghana. Tropenmed. Parasit., 31, 479-485 161. l{alrh, J. F., Daviea, J. B. & Cliff, B. (1981) WHO onchocerciaeia control Programe in the Volta River Baein in Blackfliea, Laird ed. Acad. PreEe.' 85-103 Wa1ah, J. F. grailmeS (1977) Problem of nigration of vectors of onchocerciasis t{aleh, J. F., Davies, J. B. & Gams, R. (1981) Further studie8 on the Onchocerciaais Control Progra"-re by Sirtrliuu damroeua e.1. The e aioo of control activities into eouthern Ivory Coast during 1979 lilanson, M., Courtois, L. R. & Lebied, B. (1949) Lrdradicat L6opoldvil1e. Ann. Soc. belge Mdd. trop., 26, 373-403 in control pro- 70-84 reinvaeion of the ffects of an exten- . Tropenmed. 152, 163. Parasit., 32, 269-273 I{alsh, J. F., Davies, J. B. & Le Berre, R. (1979) Entonological aspects of the first five yeare of the Onchocerciasis Control Progremne in the Volta River Basin. Tropenned. Parasit., 30, 328-344 164. Walah, J. F., Davies, J.8., Le Berre, R. & Garms, R. (1978) Standardisation of criteria for asseesing the effect of Sinuliun control in the Onchocerciasis Control Pro- gra'Ene6. Trans. R. Soc. trop. Med. Eyg., 72, 675-676 165. Waleh, J. F. & Garms, R. (t980) The detection of plant sugars in Sinulium damrosum s.1. by meana of the cold anthrone te6t. Trans. Roy. Soc. trop. Med. Ityg. ,74,811-813 a 155. ion du Siuuliun damrosum b 167 . White, P. T., Coleuan, M. & Jupp, B. P. (1982) Swamp rice developuent, Schistosomiasis and Onchocerciasis in Southeast Sierre Leone. Ar.. J. trop. Med. Hyg., 31,490-498 168. Wolf, H. et al. (1979) Quan titative studies on adult 0. volvulus after treatuent with sura,Ein and metrifonate. Tropenmed. Parasit., 30, 134 169. Zerbo, G., Sowah, S. A. & Mullen, K. (1984) Redispersion radiaire et lin6aire des siuulies uigrantes du comp lexe S. daonosum en Afri que de lrouest. I. Dispersion radiaire. Cahiers OR.STOM sdr. Ent. m6d. parasit. (sous presse) B. RAPPORTS* PERSONNAI,ISES 172. Agoua, H. (1983) Etude prdlininaire de ta dur6e de vie larvaire de S. damrosun s.1. eur troisriviEresdeC6tedlIvoire.Doc.Travai1R.S.No, 5 pages 173. Balay, G. (1968) Rapport sur 1'enqu6te entoruologique dans les foyers dronchocercose de lrouest de la Ripublique du Niger. Uoc. ron6ot. OCCGE Centre Muraz N" 15 8, 33 pages t7 4. Barbiero, V. K. (1982) Studies on the vectorial capacity of members of the Sitnulium damrosum cooplex in southern Togo. Rept ocP/vcu, of wIIo consultancy, lEBf,38 pages * Les rapports peuvent 6tre obtenus soit auprEs d|OCP, soit auprEs des organisnes qui les ont dmie et sont Eentionnds dans la bibliographie. 175. 176. 177 . 178. 185. 186. t 89. ocP /84.3 PaSe 111 Ctanet & Some. Rapport sur le repeuplement des va116es libdrdes de lronchocercose dans ltouest vottaique (secteurs i" f. Como6, de la L6raba, de Sananddni et de St-Pierre). Rapp. int. OCP. Nov. 1983. 33 pages + 8 cartes Dadzie, A. y., Rolland, A. & Thylefors, B. (1984) L'6valuation ophtalmologique du Pro- grame de Lutte contre I ronchocercose dans la r6gion du bassin de la Volta : r6sul- tats apras 7 A 8 ans drop6rations de lutte ins la Comission de Stratdgie i long Terme, 1984 ecticides. Rap . int. OCP rddig6 pour Dejoux, C. (1978) Pesticide toxicity. Field evaluation at suall and mediuu scate. Doc. nl qo€, olsr wllo/ocPlswc.L78-79, 5 pages Dejoux, C. (1978) Impact of insecticide treatmentg against Sirnuliun lanrae on the non target fauna. Ooc. min6og. WIIO/OCp/SWC t978, 8 pages Dejotur, C. (1980) Effets mrrginaux de la lutte chinique contre Siuulirn damrosum. Tech- niqueedl6tudes.Rapp.rnirn6og.oRSToMBouak6,No34,54pafl 179. 180. Dejoux, c. (1981) Introduction i lrhydrobiologie trop ry], 71 pages icale. Rapp. nin6og. ORSTOI{ Bouakd 18r. Dejoux, C. & Elouard, J. M. (1975) Etude quantitative de lrentmofarme aquatique. M6tho- dologie et normalisation. Rapp. nin6og. OP"STOM Bouak6, N" 191 , 1 1 pages 182. Dejoux, C., Elouard, J. M., Forge, P. & Maslin, J. L. (1932) Catalogue iconographique des insecteg aquatiques de C6te drlvoire. Rapp. nin6og. ORSTOM Bouakd, N" 42, 178 pages 183. Dejoux, c., Elouard, J. M., Jestin, J. M., Baker, R. D., Fairhust, c. p. & Lee, E. E.(1980) Onchocerciasls Control Progranme. Aquatic sunreillance, structure of uonitoring-Invertebrates. Rapp. Univ. Salford TOM, 23 pages 184. Dejoux, C. ciels. & Venard, P. (1975) Efficacitd comparde de deux types de substrats artifi- N" 3, 15 pages Elouard, J. M., Dejoux, C., Troubat brds benthiques de la Marahou6 , J. J. & Forge, p. (1979) Les peuplements drinvertd- avant son traitement au tdmdphos . Rapp. nin6og. ORSTOM Bouak6 N" 28 70 pages Escaffre, H., Brunhee, J., s6chan, y., carlsson, G., stiles, A., Kulzer, A., pawlick, o.& Merterrs, J. (1974) Lutte contre S. damrosumvecteur de lronchocercose enAfriquede 1'ouest. vrr. Les applications p"r haiLottlre de nouveaux insecticides et de Itr1 ORSTOM Bouaki , dans la r6gion de Korhogo, C6te(Trad. anglaise WHO lwC 176.620) nouvel les f ormulations cBo / 207 / 0NCHO I TECH I 7 4 Gui11et, P. (1981) Bref a Rapp. interne IRTO i Gui11et, P. (1981) with eophasis ron6ot. OMS G d'Ivoire. Rapp. OCCGE 187. Grouzis, M. (1983) probl}mes de d6sertification au Burkina Faso. S6oinaire IINESCO.Juin 1983. Ouagadougou. Doc. Rondot. ORSTOM Ouagadougou , 9 pages 188. percu les problbmes posis par les foruulations oicroencapsuldes. , OCP et VBC Efficacy of bacrerial pathogens in field trials against blackfries on particulate content of nater, formulation and strerm size. Doc. enEve. TDR/BCV/SWG/81 / 190. Guillet, P. (1982) Comparison of rhe results obtained with comparable method on the sameinsecticide as in temperate climates, b) in Africa, and their influence on testing strategy for onchocerciasis vector control. Doc. roneot. ocP - vBc/ocP lrc l8z. 3/w. P.3 191. Hawking, F. (t978) Diethylcarban,,zine. A review of the lirerarure with special referenceto its pharuacodynamics, toxici ty and use in the therapy of onchocerciasis and otherfilarial infections. Mimeos. doc. wHo/oNcHo 178 .142 ocP f84.3 PaSe 112 L92. 193. llerivouet, J. P. (1983) Btlan de I'occupatlon des terres prot6g6es de 1'onchocercose apreg 1oansde1utteantis1mu1idienne(BurkinaFaso,l,ta1i).@, 16pages+6cartes L94. Heee (1975) Ttre relatlonshlpe of physlcal modlficatlons and water Eanagement of rlver Bystems to the Onchocerclesls Control Progr rtilne . Rapp. lnt . OCP . 1976 195. Bltchen, C. S. & Golny, H. H. (1965) Note on the control of $lglltmr darnosum ln the regtonoftheKa1nJtDamProJect,NorthernN1ger1a.r.lrffios.+r L96. Bughea, t'1. E. (1949) Aeeoclatton of populatlon changes wtth blindnesa rates in the Kaaaena-Nankannl Dlvtelon of Navrongo Dtstrlct. Doc. non oub 116. Arch. nattonales du Ghana, Ref. Health 34 Hawklng, F. (1978) Suramln. A revlew of the literature with special re pharmacodynanlcs, toxiclty and use ln the therapy of onchocerctasls wno/oxcuo/zg. r+s ference to tts . Doc. m1s/eog. L97. 198. 199. 200. 20L. 2o2. 203. 20,4. 205. 206. 207. 208. Jonback, H. (1954) Descrlptlon of a trough testlng technlque useful ln evaluattng the effectlveneea of chemlcalg as blackf ly lanrlcldes. poc. nfm/eog. wltO/oNqrO/28.64 Jaornback, H. (1982) Rapport fln-r de contrat. Raoo. Lnt- ocP. 1982 Kurtak' D. (1982) Interpretatlon of results of tests for cross reslatance sith lanrae of Xlmullum dannoeum e.1. Rapp. lnt. OCp. 1982 Iturtak, D. (1983) to t@pho8. Suecepttblllty of ocP. 15 , 6 pages tfurtak, D., Ouedreogo, M., Ocrao, M., Tele, B. & Gulllet, p. (1982) preliminary note onthe appearance 1n Ivory Coast of resistance to chlorphoxlm ln Slmullum sanctlpaull/S. eoubrense lanrae already reslstant to temephos. WHO rir.og. Dffi s. Btr./S. "trb.^t- at Ndeoou, Bandma, Le Berre, R. (1978) Prtnc Slmullum dannosum. riples, method Doc. mlm6oe. s and applica ocP/swc/78.L4 tion equipment for the conErol of , 8 pages Le Berre, R. (1984) ttDe tout un peurl Raoo. lnt. OMS F6vrier 1984 1O pages Le Berre, R., Egcaffre, H., Pendrlez,8., Grebaut, S. & pangalet, p. (1972) Lutte contreS. d-noguo, le vecteur de l'onchocercose en Afrlque de 1'Ouest. II. Eseals de nou- veaux lneectl.cldes et de nouvelles formulatlone en traltements conventionnels. (trad anglalse wttofwcf te .O:l:y Le Berre, R., Phtllppon,8., Grebaut, S., S6chan, y., Lenormand, J., Etlenne, J. &Garetta, Ph. (197f) Lutte contre Simulium damnosum le vecteur de I'onchocercose en Afrlque de 1'Ouest. I. Essals corpl6mentaires de nouveaux lnsecticldes. (Trad. anglalee wHo/VB.C/ 76 .6L4) Ifvdque, C., Abban, E. K., Curtts, M.(1982) Report on fish populatlons OMS/OCP, 51 pagee S., Falrhurst, C. R., Jestln, J. M. & paugy, D. ln rlvers of Ivory Coast and Ghana. Doc. oln6og. Bouak6, N' 23 , 55 pages Maslln, Y., Albaret, J. J., Blgorne, R., Herbinet, p., L6v0que, C., Merona, D. de & Paugy, D. (1978) Evolution des peu, traiteErent A 1'Abate. Raoo. mim6oe plements ichtyologlques de la Cono6 depuls son Maslin, Y., Merona, B. de, Albaret, J. J. & Bigorne, R. (1978) Evolution des peuplements lchtyologlquee du Nzi depuls son traltement au chlorphoxlne. Rapp. n1m6og. ORSTOM Bouak6, N' 22, 1o3 pages 209 Meredlth, S. E. O. & Davles, J. B. the llggflgjamnosum complex. ocP /84.3 page 113 (1981) Variatlon and distrlbutlon of the cytotyPes of Doc. lnt. OCP. 1981 Dyna- 18 pages 2IO. Merone, B. de, Abban, E. K., Herbinet, P. & Sape, E. R. (1979) Peupleuents lchtyologlques des blotopeg d'eaux peu prof ondes des rlviEres du nord au Gtrana. Rapp. mfin6og. ORSTOM Bouak6, N" 31 , 23 pages zLL. Mondet, B. (1979) Etude de Ia posslbilit6 d'utllisatlon des n6matodes pour une biolog simulies vectri-ces de I'onchocercose en Afrlque de Raou. 79 212. ?L3, 2L4. 2L5. 2L6. 2L7 . 2L8. 2L9. 220. lutte 1'Ouest. Mouchet, J. (1982) Vector Control at Cmunlty L€vel. Doc. mlmdo s, wtro/vBc/I2.842 Mullen, K. (1981) A conparison of the precision of four methods of calculatlng Annual Transmtsslon Potentlals. OCP internal Rpt, 2O Pages }tulIen' T. (1981) A note on calculating the Annual Bltlng Rate. WIIO oimeog. Doc. OCp/!1!!1-1, 2 pages Ooar, Mt S. & Schulz-Key, H. (1976) Acid phosphatase acttvtty of Onchocerca volvulus u1crof11ar1aefrooWeetAfr1caandC,uatema1a.M1,"og.Do".ffiPa8es Parls' F. (1980) Etude gEographique d'une zone d'end6mie onchocerqulenne: Bougourlba,Volta Nolre. Doc. ORSTOI1 Ouagadougou, 21 pages + cartes Parle' F. (1983) L'occupation des va116es de la Bougouriba et de 1a Volta Noire uigue de l'habltat et des culturee depuls 1974. Rapp. lnt. OCp. Nov. 1983, * 7 cartee son traltement A 1'Abate. Rapp. mlmdo s. oRsToM Equak6, N" 30 , 106 pages Philtppon' B. (1977) Rappel concernant la canpagne FEDoCCGE de lutte contre le vecteurde 1'onchocercose (1960-1974) c. R. 17Eme conf. tech. occcE, 341-353 Paugy, D., Blgorne, R., Albaret, J. J., Herbinet, p., & Merona, B. de (1979) Obsenratlons sur la far.rre Ptrtllppon, 8., Sichan, Y. & Escaffre, H. (1973) Lutte con 1'onchocercose en Afrique de l.Ouest - V - Etude de k.y' H., Maslln, Y., L€vOque, C. ichtyologlque du Sassandra avant tre S. d um, vecteur de 1'action insecticlde de 1'Abate Trad. laise ln2@ ,CB ippliqud d'avion par vide-vite en saison sEche. wto/wc/ 76 .6L8 ( 1976) I 22L. 222. Prost, A., Ttrylefors, 8., Palrault, C (1975) M6thodes d,€valuation 6pld€mlologlque de maase de I'onchocerco se. Leur utllisation au cours d'un progranme de lutte contrele vecteur. Comrrunic ati.on au Comtt€ d' xperts de 1'E id le de I' OMS, GenEve, 10-18 novembre 1975. t 5 , 21 pages 223. Qu6lennec, G. (1982) Prograrrme de recherche acc6l6r6 sur 1es lanricldes antlsloulldlens .Doc. ocP.82.5 pr6sent€ au CCP de 1982 Qu1116v6r'e, D., Escaffre, H., pendrlez, B., Grebaut, S., Duchateau, B.r Lee, c. w.Mouchet' J. (L972> Iiltte contre S. damnosum, vecteur de 1'onchocercose en Afrlquede l'Ouest- III. Appllcatlon par avion en saison des pluies. M6thodes d'appllcatlons, nouvelles formulations. IIIa. Tableau r€sum6 des tests par applicatlons a€rlennes et conventionnelles de nouveaux insec ticides et de nouvelles IPhlllppon, B., Sechan, Y., RlviBre, F., Kulzer, H., pawllck, O. & Krupke, M. (1973)Lutte contre S. damnosum' vecteur de 1'onchocercose en Afrique de l.Ouest - VI -Pulv€rleation de nouvelles fo:mrulations d'lnsecticides par h61lcoptEre en salsondes plules en zone de savane guin6enne. Trad. anelalse wHo/vgc/75.619 (1970) I occcE 1 10 Nov formulatlons. Rapp.anglaise 224. YB 6 6 L97 6) 1 t19 6c. L972 (!rad. ocP f84.3 Page 114 225. 233. Traore, S., H4brard, G., Duval, 234. 236. Ttrylefora, B. (1978) The effect of a cmbl Levaoleole on ocular onchocerctaelc. treatEent ueing DEC and ttrro/oct/zpt/tg.t*t Qu1116v6r6, D., Escaffre, H., Pendrlez,8., Grebaut, S., Ouedraogo, J', Kulzer, H', Be1lec, C., Phlllppon, B. & Le Berre, R. (1973) Lutte contre S' damnosum' vecteur de l.onchocercose en Afrique de 1'Ouest. IV. Evaluati-on de nouvelles for:urulatlonslutte lnsectlclde. Rapo.1ar Per h611cop tere et simulatio o 5 anv. 1 T 226. Renz, A. (1983) Studles on the relnvasion by Sfunulium damnosuo s.1. tnto the eagtern areas of OCP and on the vectorial capacity of differents spec les of the S. damnosuro corplex in Togo and Benln ln 1982. WHO Consultantshlp Repor t. 28 JuIv to 31 october n d'une oo6ration de ," rad. r{t[o/JwL L9A, 52 pagee Rolland, A. (1975) Relatlon entre onchocercose et zone d'habltat : r6sultats de 1'6tude g6ographlque et n6dicale d'un terroir de la Volta Rouge (Densln, Nobere, Ilaute volta). poc. ntmdoe. ous ceneve wtto/oxalo/wP/25.21 A narklng and recapture experlnent on poc. nrndoe. wtto/oncno/Zz.9A, 13 pagee 227. 228. Roorn, B. (1979) Irs polsaona dee haute basslns de la Volta. Rapp. rir6og. Inst. Polytech. Ouagadotrgou, 21 pages 229 Strtzner, B. (1979) The effects of large scale field appllcatlon of chlorphoxlm on the benthtc lnvertebrateo In the Nzl River, Ivory Coast. napp. rnlndoc. tmO/OgP, 72 pagee 230. Ttrmpaon, B. H., lrlaleh, B. & lJalah, J. F. (L972) Slnutluo donoetltr and blonoolc obeerivatlong. 23L. ned lntermlttant Doc- mln6oq- OCP. 232. Traore, S. & H6brard, G. (1983) Bto6co logle et caract€rlstlques vectrLces naturelles des feuelles du tl 11 en C6te d'Ivolre. Doc. ron6ot. OCCGE N'2 51 pages J. & Faye, caract6rlstlques vectriceg naturelles du grou Pe zone de savane. Doc ron6ot O. (1982) Etude de la bio6co etd oubren sanctl rate and annual transmisslon ea 11 en 82 Traore, S., Phlllppon, B. & H6brard, G. (1980) Rapport des enqu6tes r€a11s6es dane la r6g1on du Parc natlonal de Taf. II. L€ bas Sassandra. Doc. rondot. OCCGE ORSTOM, w' zs/ollcuo/nnp.ao Waleh, J. F. (1970) T'he contro tarles ln relation to the 1 of Simullttm dannosum ln the Rlver Niger and lte trlbu- I l,ake Research proJect, coverlng the Perlod 1961 to 1969. Mlmeo l 237. 238. Walah, J. F. (1983) A conslderatlon potentlal: their relationshiP limitatlon of thelr usefulness. Trav. R. S. N' 14 oct. 1983 of annual bltlng to each other and Raoo. OCP. Doc. to the epldemlological data ; the , 27 pages Walsh, J. F. (1984) l.lemorandum to VCU on the lmportence of S. soubrense in the savanna. Doc. lnt. OCP. 1984' 8 Pages t NPf84.3 paSe 115 2t+O 24L. 242. 243. 244. c. RAPPORTS At{Otry-!4ES Onchocercose. Slmptonatologie, anatomopathologie, dlagnostlc, sous Ia dlrectlon de A. A. Buck. oMS, GenEve 6a. L974, 84 pages Accord cadre pour le Programe de Lutte contre I'Onchocercose dans Ia r6glon du bassln de la Volta. 1er novembre 1973 Accord portant cr6atlon d'un Fonds de Lutte contre lrOnchocercose. 7 srai 1975 Accord relatlf au Fonde pour ltonchocercose. 19 septembre 1979 Anonyme 1959 - Jolnt USAID^CCGBIHO technic claels control Tunle, 1. 8 July 1958. al meeting on the feaslbl 11 ty of onchocer- Mimeoc. Doc. 69.75 245. Anonyme L973 - Contr0le de 1'onchocercose dans la r€gion du baseln de la Volta. R.epport de la ulsslon d'assi stance Dr6Daratoire (APG) aux de Burkina Faso. COte d'Ivol , Dahomey. Ghana. Mali. Nl.ger. Toeo. GenEve, 1973 (PNIID' FAO, BIRI) er o!rs) 246. Anonlrue Lg77'- CrltEree blm6dlcaux pour le repeuplement de l'alre du progranme de Lutte contre 1'Onchocercose dane le bassln de la Volta. Rapp. d'un groupe de travall.6-8 tuin 1977 ocp/srt/tt.t 247. 248. 249. Anonyue 1978 - RaPPort de la 5!me seselon du Cqrit6 conJolnt de Coordlnatlon du programede Luttc contre l'Onchocercose dans la r€glon du bassln de la Volta, 1978 Anonlrue L97E' Progrme de Lutte contre I'onchocercoee dang la r6glon du baegln de laVolta. Rapport d' €valuatlon 1975-197g Anonynre L979 - RaPport de la 6Ene eeselon du Cmtt€ conJolnt de coordlnatlon du programede Lutte contre 1'onchocercose dans Ia r€glon du bassin de la Volta. 3-5 d6cenbre1979, GenEve Anonvme L979' Flche technique du B.t. H-L4 wP,o/vBc/7g.75o Anonyme 1980 - courlt6 conJolnt du Progranme de Lutte contre 1'onchocercose dans la r6glondu bassin de ra volta. Rapport de la premlEre sesslon. ynnoussoukro. C6te d,rvolre,25-27 novembre 198O Anon1rue1980- 5Eme rapport du cotrlt6 oMs d'experts de 1a Blologle des Vecteurs et de laLutte antivectorielle - 1980 - R6sistance des vecteurs de maladles aux pestlcldcs.Sdr. Rapp. techn. N'655r OMS GenEve ed.,19gO, g9 pages ?54. Anonyne 1981 Ocular onchocerctasis 250. 25L. 252. 255. 256. Rpt. t o EAC, GenEve ocP/EAc. z , Five years after cmenclng vector control. 3 .1981 Anonlmre 1982 - corltE conjoint du Progranme de Lutte contre I'onchocercose dans la r6gtondu baaeln de la volta. Rapport de la trolsleEe sesslon, Bmako, 7-Io dEceubre I9g2 Anon)tme L982 - Rapport sur Ie d6veloppement soclo-dconomlque des zonee prot6g6es de1'onchocercose eu B6n1n pr6sent6 A la trolslEoe sesslon du CCp, Bameko, l9g2(polnt 3.4.A) Anonlme 1982 - Rapport sur le d6veloppeurent soclo-6conomlque des zones prot6g6es del',onchocercose au Ghana pr6sent6 a Ia troislame session du ccp, Banako, 1gg2(polnt 3.4.B) 257. t I ocP f84.3 paSe 116 258 Anonyme 1982 - Rapport sur Ie dEveloppement socio-6cononrlque des zones prot6g6es de 1'onchocercose au Mall pr6sent€ A la troisiEme sesslon du CCP, Bamako, L982(polnt 3.4.C) Anonyue L982 - Ttre pathogenesls and treatment of ocular onchocerclasls : Report of the elght meetlng of the scientlfic worklng group on fllarlasis ln collaboratlon wtth the progrome for the preventlon of bllndness. Doc. mirndog. OMS. GenEve TDR {1 "G (gr /az.r Anonyne 1982 - L'onchocercose dans la r6gion de Bandiagara. Epid6uriologte et lutte. 259. Actlons et r6sultats d'OCP. Doc. lnt. OCP. 15 oct. L982, L2 Pages 26L. Anonyue 1982 - L'onchocercose dans la r6glon de Seltngu€, l.tall . Epid€mlolo8,le et lutte Actlon et rceultats d'OCP. Rapp. int. OCP 1982, 11 pages 263. Anonlme Lg82 - The I{IIO Pesticides Evaluarion Scheme. Doc. mim6oc. @1S - wttO/vrcl12.84b and wHo/vBc{82.854 Anonyue 1983 - WHO lnfornal consultatlon on IGR-Geneva, August 1983. WHO/VBC/83.883 260 a 264. 265. Anon;iue 1983 - Ineectlclde requtrements for pub llc health. !&tQ/pestlcf de Eqn14IeslullEg lndustrv meetlng, GenEve 13-14 luln 1983 . Doc. 83 .3 25 pages 266 Anonyne 1983 - Coott6 conjolnt du Progroe de Lutte contre l'Onchocercoee dans la r6glon du baaetn de la Volta. Rapport de la quatrllme seealon, Parls, L2-L5 dEceobre 1983 267. Anonyuc 1983 - Rapport eur 1'6valuatlon de nouveaux lnsectlcldes pr€eent6 I Ia quatrlEoc sceclon du CCPr Parle, 1983 (polnt 5) 268. Anon:rme 19E3 - Rapport dtactlvtt6 de 1'Ol,lS A la quatrlEne seeslon du CCP, Parlc, 1983(polnt 4.2) 259. Anonlrue 1983 - Rapport aur le d€veloppenent Boclo-6conorlque des zones prot6g6es de 1'onchocercose en Cate d'Ivolre pr€sent6 I la quatrlEoe sesslon du CCP, Parlsr 1983(potnt 4.4.A) 27O. Anonlrue 1983 - Projet Say: Rapport €con@lque mal 1983 pr€aentE A Ia quatrllme acealon du CCPr Parls, 1983 (point 4.4.8> 27L. Anon;rue 1983 - Rapport sur les actlvlt6s de mise en valeur des zoneg prot6g6es de 1'onchocercoae au Togo, pr6sent6 I 1a quatriEme session du CCP, Parle, 1983(polnt 4.4.C) 272. Anonyme 1983 - Rapport sur le ddveloppeurent 6conooique et soclal des zones prot6g€ee de 1'onchocercose en Haute-Vo1ta (juillet 1983) pr6sent6 A la quatrlEme sesslon du CCP, Parls, 1983 (polnt 4.4.D) 273. Anonyue 1983 - Progra.me de Lutte contre l'Onchocercose dans la rdglon du bassln de la Vo1ta. Rapport de la quatriEme sesslon du Conrit6 consultatif d'experts. Bouakd, 26-3O sept. 1983 274. Anonyme 1983 - Prograrure de Lutte contre I'Onchocercose dans la r6glon du bassln de la Volta. Rapport de la quatriEme session du Comit6 consultatif d'experts. Bouak6, 26-30 6ept. 1983. Annexe III. Rapport de la quatriEme session du Groupe dcologlque. Anonyne 1983 - Rapport de la rEunion annuelle pour 1983 des hydroblologtstes charg6s de Ia surveillance aquatique des rlviEres de la zone du Progranrne de Lrrtte contre 1'Onchocercoae. Rapp. int. OCP. 1983, 15 pages a 275. 276. 278. NPf 84.3 PaSe 117 Anonyue 19E3 - T6ldtranemleelon des donnEes hydrotoglques dens la lutte contre @!][ daongqr.rm. R6unlon lnforuelte, 15-15 mars 1983, OCP, Ouagadougou. Doc. mlndog. dcpa=v,vcaTmtJat .t 1) furnlshed by llellccme /vcu/ozst. r6v. 1e84 277. Anonlrue 1984 - Evaluatlon of formulations of permethrln (OMS 182 ae larvlcldea agalnst, Sl.mulium damnosum s.1. Rapp. int. OCP 279. Anonlme 1984 - Strat6gle A long terme du Prograure de Lutte contre l'Onchocercose dans Ia r6glon du bassln de la Volta. 25 nal 1984(2). Annexe 4. Identlftcatlon des zones op6ratlonnelles du Progro'rme. Anonyne 1984 - Evaluatlon g6n6rale des progrEs r6a1is6s dans la mlse en oeuvre du plan d'actlon contre 1a d6sertlftcatlon entre 1978 et 1983. Rapport au Consell d'adminls- !!a!lon du PNUE, 1984 f I { ocP f84.3 PaSe 118 ANNEX 1 1 LISTE DES DOCTJMEMS DE TRAVAIL FOI'RNIS PAR LES CONTRIBUIEURS POUR I.A REVT'E SCIENTIFIQT'E Ttre Onchocerclasls Control Prograrmne ln the Volta rlver bastn area ln Weet Afrlca - by J. D. t'!,arr OCP Strategy and lts evolutlon - by F. Walsh OCP Aerlal operatlono - by F. Walsh Larvlclde appllcatlon equlpment developoent and evaluatlon - by D. A. T. Baldry and B. Cllff Trrltemente larvlcldee. R6seau hydrographlque tralt6. Volure et mode de tratternent - par J. Dlouchet Entooologlcal evaluatlon and results of treatment - by F. Walsh and G. Zetbo Relnvaalon of OCP by specles of the S. damnosum couplex - by R. Garms Dleperelon radtalre dee elmrllee olgrantes - par G. Zerbo, S. A. Sowah et K. lfuller Maletance aux tneectlcldee chez S. daonosum - par J. Mouchet, D. Ifurtak, P. Gul1let et B. Phlllppon Evaluatton 6p1d€ulologlque. Les grappes g6ographlques - par A. prost Leg r6cultate 6pld€olologiques du Progranme - par A. prost l,!orta11t6 des parasltes adultes - par M. Karam L'6valuation ophtaloologlque d'ocP - par A. Rolland, K. y. Dad.zle et B. Ttrylefors A conslderatlon of annual blttng rate and annual transoisslon potentlal; thelr relatlon- shlp to each other and to the epideolological data; the llnltations of their use - by F. Walsh Relatlon entre les nlveaux de transmlseton et les falts clinlques dans 1'onchocercose - par A. Prost l'torphologle des stades pr6inaglnaux du complexe S. danosuo en Afrique de I'Orest - parD. Qul116v6r6 cyEotaxonomy of the sluuliuo dmnosum cmplex - by S. E. o. Meredith I8 The ldentlftcatlon of adult members of the Sluullun dq.s", spectes cmplex - byR. A. Cheke 2 3 4 15. 16. 17. 5 6. 7. 8. 9. 10. 11. L2. t3. L4. 19. 20. 2L. 22. 23. t The agelng of adult Simulluo damnosum s.l - by R. A. Cheke Blochemlcal ldentlflcatlon of oembers of S. damnosum cooplex - by S. E. O. Meredlth Blo€cologle des slnrllee adultes - par D. Qu11l6v6r6 Blo6cologle dea atades pr6funagtnaux dea eluullee - par J. M. Elouard caractErletlquee vectrlces des fenelles du cooplexe s. damnosum en Afrlque de l,ouest - par D. Qu1116v6r6 n 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 37. 3E. 39. 40. ocPf 84.3 Page 119 Annex 1 Echanttllonnage des larves de slmulles - Par J. M, Elouard Echanttllonnage dee elnullee adultee - Par Ch. Bellec Rearlng and colonlsatlon of the S. daunosuo complex - by J. Raybould Nutrltlon dea larvee du cmplexe S. daonoeuo - Par P. Gr.rlllet Dur6e de v1e larvalre de S. dmnosuo eur trols rlvlEree de C6te d'Ivotre - per Il. Agoua Recherchee eur Ie paraelte - par M. Karao Ecologle humalne ,et onchocercoae - per A. Prost Recherches concernrnt la toxlcltd de nouveaux lnsecttcldes - par C. DeJoux Survelllance Ecologlque dea mtlleux lotl.ques - par C. DeJoux Le d6veloppe@nt de nouveaux lneecttcldea et de nouvellee technlques de lutte contre les stmrlles - par J. l,l,ouchet Chlolothdrap!.e de 1'onchocercose - par A. Rougeuont Role of oodele In planning of future strategiee by ocp - by J. B. Davies Tlre econoolcs of Bllndaess Preventton under the Onchoc.erclaale Control prograo ln UpperVolta: a prellolnary analyele - by A. Prost, N. Preecott and R. L Berre L'lrpact coclo-culturel d'OCp - par C. patrault L'lopact d'OCP sur la sant€ dee populatlons - per H. Blanc Partlclpatlon dee cmunaut€s l la lutte contre l'onchocercoae - per J. Mouchet Formatlon du personner a ocp - par J. Mouchet et L. Ravelonanody t 34 35 36 t a ( a ocP/84.3 Page 120 ANNEX II LIST OF FIGURES AND TABLES Life cycle of Onchocerca volvulusFig. Fig. Fig. Fig. Fig - Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. rig. Fig. I 2 3 4 5 6 7 8A 8B 9 10 11A 118 L2 13 L4 15 16. L7 18 19 20 Onchocerciasis in Africa and the Americas Organigram of the Programne Organizational char! of Onchocerciasis Control Prograrmne in the Volta River Basin Phytogeographical zones of the Prograurne The different phases of the larviciding operations Maximum extension of aerial larviciding in August 1980 Aerial larviciding reduced to minimum, end of April 1983 Page 8 9 11 15 16 19 22 26 26 34 35 37 37 40 44 t Comparative tTp ratios in Prograrme area as a whole ABR The Prograrmnets operational zones (OOZs) Annual transmission potentials prior to operations Annual transmission potentials, November 1982 - October 1983 Reinvasion zones in inicial OCP area and sources of migrant blackflies The resistances in the Simulium damnosum c omplex Trend of mean microfilarial load of comunities in the different zones of the Prograruoe Trends in parasite infection load among adults of different cormrunities Trend of ocular onchocerciasis in the village of Mouvielo before and after vector control was initiated Main zones with economic development projects, from the PAG mission to the year 1983 Dynamics of occupation of valleys under control (Burkina Faso - Mali, Novenber 1983) Distribution of cytot,ypes of the Simulium damnosum complex Diagram of multiple-gutEer aPParaEus 52 52 54 64 a 70 79 99 ) ocP/84.3 Page LzL Annex II t Table 1 Table 2 Table 3 'l.ab 1e 4 Table 5 Table 6 Table 7 Table 8 Timetable of the various phases, areas and lengths of river under treatment Insecticide consumption and flight hours in OCP Entomological monitoring points Evolution of percentage of catching points for each category of ATP in the initial Prograrune area Reduction in prevalence in the Programme area Incidence of onchocerciasis in four villages of the Farako focus between 1971 and 1983 Relations between ATP and epiderniological variables Training activities carried out or supported by OCP between 1975 and 1983 Page 23 28 30 38 50 55 59 98 I a t ) ocPf 84.3 paze 122 ANNEX III l,lission dlAeaietance Pr6paratoire aux GouverneEentg AutoritC pour 1'Am6naSeoent dea VaI16ea der Volta Banque Africaine de D&eloppeoent Banque Internat.ionale pour la Recons- truction et le D6veloppeBenE Comitd dea Agencea parrainantee Comit6 Conjoint de CoordinaEion(du Programe) Conit6 Coneultatif drExperEa(du Programs) Cooi16 Conjoint du Programe Comit6 Consultatif Scientifique et Technique Conpagnie Ivoirienne de D&eloppeoent deE Textilea Organisation dee Natione Uniee poqr lrAgriculture et I rAtiuentation Fonds Europ6en de Ddveloppeuent Institut de Recherches sur 1a Trypano- somiase et lrOnchocercose, Bouakd, C6te dr Ivoire 0rganisation pour la Collaboration et la Coopdration pour la lutle contre les Grandes End6uies, Bobo Dioulasso, Burkina Faso Progranme de lutte contre lrOncho- cetcose dane la r6gion du Bassin de la Volta ProJrr chirnlochlraple dc ltOncho- ccrcoec Organieation Mondiale de 1a Santd Organiaationr non Couverneoentslea Office de la Recherche Sciencifique eE Technique OulreEer OrganieaEion des paye ExporEaleurg de Pdtrole APG AW BAD BIRD CAP ccc ccE CCP ccsr CIDT FED IRTO OCCGE ocT oMs ONG ORSTOM ABREVIATIONS PAG JPC STAC FAO EDF ocT I{HO NGO ADB csA JCC EAC Mission of Preparatory Assistance to GovernmenEs African Development Bank Comitcee of Sponsoring Agencies Joint Coordinating Comittee Expert Advisory Comittee Joint Programe ComiEtee Scientific and Technical Advieory Co@itte Food and Agricultural Organization European Developtuenf Fund Trypanosomiasis and Onchocerciasis Research InstiEuEe Onchocerciasis Control Prograrme Onchocerciasis Chemiotherapy proj ect World Healrh Organization Non Governoental Organizations ? 0cP I t a Ddnmination frangaiac SigIe frangais S igle anglaia D6nonination anglaise OPEP OPEC I ABREVIATIoNS (suite) ocpf aq.t page 123 Annex III Annual Transmission Potential Monthly Transmission PotenEial United Natione Development Progrerme Annual Biting Rate tNDP/WORIJ BANK/WHO Special programe for Research and Training in Tropical D leeaae e Monthly Biting Rare United NaEions Education, Science andCultural Organization United State6 Agency for International Development VecEor Biology and Control (a WHOdivision) Vector Control Unit (in OCp) OCP Operational Zone a Ddnomination f rancaiae PoEentiel Annuel de Transmisaion Potentiel Menauel de Tranemiseion Programne dea Nationc Uniee pour le D6veloppeoent Progranrne dea Nettons Uniee pgur I I Environnement Soci6td drAeeietance technique pour la Moderniaation de lrAgriculture efi C6tc drlvoire SociCt6 pour 1e Ddveloppeoent et 1'Exploitacion du pal.oier I huile Soci6t6 de Ddveloppenent du Riz Sociit6 de Ddveloppeoen! du Sucre Taux annuel de piqOrea PrograrEEe du pNtD/BIRD/OMS pour la Recherche et la Foruation dans lea Maladies tropicalee Taux Mensuel de piqOree Organisation dee Natione Unies pour 1'Education, la Science et la CuI t ure Agence des Etats-Unis pour le Ddvelop- PeDent Incernational Division de la Biologie des Vecteurs eEde 1a Lutte antivectorielle (OMS, Cenlve) Unitd de lutte anrivectorielle(dans Ie Progreme) Zone opdrationnelle du progra.me I'NEP Unlted Nationo Envirorurental Programme PAT PMT PNIJD PNUE SAMACI SODEPAI.M SODERIZ SODESUCRE TAP lDR ATP IftP I'NDP ABR TRD a ftP zoP MBR I'NESCO USAID vcu ooz vBc t D l ( I Sigle frangai s Sigle anglais Ddnonination anglaise I