Annual internal technical review meeting: Ouagadougou, 11-14 March 1991; includes EPI progress report and main information on delinition of recrudescence

WORLD HEALTH ORGANIZATION ORGANISATION MONDIALE DE LA SANTE ONCHOCERCIASIS CONTROL PROGR,{MME IN WEST AFRICA PROGRATVTME DE LUTIE CONTRE UONCHOCERCOSE EN AFRIQUE DE TOUEST EXPERT ADVTSORY COMMITTEE Twelfth session Ouagadougou. 10-14 June 1991 ocP/EACL2.6 n{GTISE ONIY ANNUAL INTERNAL TECHNICAL REVIEW MEETING OUAGADOUGOU, 1l-14 March 1991 (includes EPI Progress report and main information on delinition of recrudescence) Document OCP /DlR/gl,/@t WORLD HEALTH ORGANIZATION ONCHOCERCIASIS COT{TROL PROGRAMME IN WEST AFRICA Annual Internal Technical Review Meeting Ouagadougou, LL-L4 March \991 Document OCP/DIR/9 I /00 I da -t- Table of Contents 1 INTRODUCTION 2 oPERATIONS IN 1990......... 2.1 Larvicid 2.2 results 2.3 !pdate on resistance to insecticides in the OCP area. 2.4 Epidemiological Evaluation Activities 1990 3 OCUI..A,R DISEASE PATTERNS AND PARASTTE STRAINS 1, 1 1 2 3 3 4 4 5 5 7 7 8 9 9 9 9 10 11 11 11 t4 L4 3.1 Ocular Disease pattern in the OCP ........ 3.2 DNA Probes for differentiating Forest and Savanna Strains. 3.3 Further studies and operational applications of DNA probes. 4 IVERMECTIN 4.1 Ivermectin distribution in the Western Extension 4.2 Southern Extension and reinvasion areas 4.3 Adverse reactions 4.4 4.5 4.6 Effect on transmission. 4.7 Passive ivermectin treatment .... 5 MODELLING.... 5.1 Priorities. 5.2 risk and control of recrudescence 5.3 5.4 6 ORIGINAL OCP AREA.............. 15 6.1 levels after cessation of larviciding .. 6.2 6.3 6.4 6.5 ........ 15 ........ 16 ........ 18 Epidemiological lmportance of Infected Plan for cessation of larviciding in 1991. Migrants. 18 t9 7 DIAGNOSTTC TOOrS ................. 19 7.1 7.2 7.3 ................. 21 8 BRIEFING ON INTRA.UNIT RESEARCH ACTIVITIES. 8.1 Insecticide research. 8.2 8.3 8.4 20 22 22 23 23 24 248.5 Hydrology and I3 head Larvae New 9 OPERATIONAL PU\NS FOR 1991. 9.1 Western extensions. 9.2 Eastern Operational Area. 10 DEVOLUTION 11 DATA A}.IALYSIS A}ID COMPUTER SUPPORT 12 MISCELI.ANEOUS 13 RECOMMENDATIONS ........ Appendix A List of participants .... Appendix B. List of recent OCP publications 25 25 25 25 27 28 29 31 32 -ll- -t- 1 INIRODUCTION The meeting was opened by the Programme Director who stressed its importance to OCP. He remarked that the agenda was heavy but he was confident that the topics would allbecovered. Headvised theparticipantsto beconcise andscientific and avoid repeating what had already been treated the previous year. Participants were to consider the cost implications of their recorlmendations since OCP budget was getting critical and there are world-wide economic difficulties. He welcomed Dr. Remme from the TDR, Dr.Unnasch of the University of Alabama and Mr. Plaisier from Rotterdam University who were attending the meeting, and expressed his trust that their contributions were going to be useful to OCP. Finally, he noted that he was looking forward to the report of the model application to define the parameters of recrudescence. The meeting then went through the recommendations of the last meeting as well as the recommendations emanating from the research priorities of the 1lth EAC meeting and noted their relevance to the present meeting. 2 OPERATIONS IN 1990 The meeting was briefed on the last year's operations of both vCU and EpI. 2,1 Larviciding In the eastern operational zone, within the original programme area, larviciding was carried out in all the river stretches with less than 14 to 15 years of vector control or in foci where the epidemiological results were not satisfactory, (Map 1). These were the Black Volta below the confluence of the Pouene, the lower Bougouriba downstream of the Diebougou bridge (where larviciding was done during part of the rainy season only), the White Volta below its junction with the Kulpawn, the whole of the Kulpawn and the Sissili and the Oti and its tributaries below the Sansane-Mango bridge. The Mekrou was also treated upstream of the Koudou falls together with its source of reinvasion from the upper Pendjari. The Alibori and the Sota were subjected to vector control, the latter because of an unusual increase in transmission. larviciding was carried out in rivers in the southern extension in which S. damnosum species breed and where severely blinding onchocerciasis is found, (Map 1). Seasonal treatment was carried out in the tributaries to the east of the Volta t-ake where trans- mission is mainly due to S. squamosum and S. yaherue. The rainfall in 1990 was lower than in the previous year in most parts of the programme area and resulted in lower water discharges andf or intermittent flow of some tributaries such as the tributaries of the Black Volta in the Cdte d'Ivoire where the vectors did not breed during the year. L-arviciding was suspended in most cases with considerable savings in the use as well as flight hours. All six insecticides were used successfully but a lower t -3 -.L 2susceptibility with the use of pyraclofos in the river Pru was encountered ancl as a result its application was stopped. In the western extension, larviciding was started in Sierra [-eone. [n Guinea, it was extended to cover fully the upper basins of the Sassandra, Sankarani, Milo and Niandan, despite the fact that severely blinding onchocerciasis has been shown to exist only in the upper Milo basiru (Map 1). However, the presence of the severely blinding strain in the other basins cannot be excluded. Besides, though the main vectorsare S. sEtatnosum and S. soubrerce Menankaya, savanna species (damnosum/sirbanum) also breert locally. Following the EAC recommendation which was accepted by the JPC, vector control was suspended in the northern part of western Mali, Senegal, Guinea Bissau and the Fouta Djallon in Guinea. 22. Entomological results Entomological results in the original areawere generatly satisfactory in most river basins except in the Banifing IV. After 15 years of vector control in this basin satisfactory epidemiological results were recorded and it was decided to suspend larvicid.ing in 199d. However this resulted, in August, in unacceptably high vector infectiviry levet and larviciding was resumed. Suspension was attempted again in September with similar results. The early reinvasion observed in May in some points of C6te d'lvoire (Madina and Kato) lasted only a few weeks and did not result in significant transmission. For the second consecutive year, reinvasion of the Banifing basin in Mali was completely stopped which confirms the role of Nigerbasin and Northern Sierra [-eone in the reinvasion of this area. The entomological results in the Eastern Operational Zone were among the best obtained since the southern extension came under full coverage with larviciding. The reinvasion in the eastern part df the original Programme area was controlled successfully and the infiltration by invading flies did not reach the levels of the previous years. Transmission was low in most river basins notably the Black Volta (except Bui with an ATp of 168) and the White Volta (including Nakong 24).Thte ATP's of the other river basins were generally moderate and below 100. The high ATP's of over 800 recorded east of the Volta I-ake were due to S. sEtamosurn and S. yaherce exclusively. The ATP of over 600 on the river Pru was attributed to the suspension of larviciding during ivermectin studies as well as the studies on pyraclofos. Inthewesternextension,verygood resultswereobtained inmost of Guinea (Nigerbasin). However in upper Niandan where S. soubrense Menankaya breects, ATPs of up to 500 were recorded and treatments had to be intensified. In Northern Sierra l-eone trans- mission was successfully interrupted except in the mountainous area of Kabala where high ATPs of up to 1000 were observed. They were clue mainly to S. yalrcrce and .S. squanosum. the major vectors in this area which breed in streamlets ancl are very difficult to control. 3scluamosum, the majorvectors in this areawhich breed instreamlets and are verydifficult to control. In Southern Sierra lrone, despite the beginning of treatments and the low MBRs observed, transmissionwas still high because of the exceptionally high vectorial capaciry of. S. soubrerue B. 23 Update on resistance to insecticides in the OCP area. In 1990, large areas of the OCP were controlled all the year round without treatment failures due to resistance because of successful insecticide rotations. The pattern of resistance with a fixed focus on the lower Comoe Basin (5. sanctipuli, S. damnosum s.s.), and one on the Bafing/Senegal Basin (5. sirbanun ) was confirmed by susceptibility tests. Spot resistance to temephos treatment, was detected in the l.ower Sassandra and in the Baoule but it was controlled by switching to other insecticides. Susceptibility to temephos has decreased over the last fouryears in Sierra [-eone, but temephoswas still operational when used alternately with the other insecticides. Susceptibility to chlorphoxim and its replacement, phoxim, was normal everywhere except in the I-ower Comoe, where there is a fixed focus of resistance. Susceptibility to pyraclofos was also normal everywhere, and there was no indication of cross-resistance with either temephos or phoxim/chlor- phoxim. S. darnnosums.s. populations showed a slightly lower susceptibility in South-East Cdte d'Ivoire and on the Pru River to pyraclofos but current data do not indicate that this is resistance. No resistance to either B.t.H 14, carbosulfan or permethrin was detected. 2.4 Epidemiological EvaluationActivities 1990 In the year 1990 the EPI Unit carried out a heavy schedule of activities consisting of either mapping, evaluation or ivermectin treatment in over 2200 villages. The mappingof thewesternextensionareawas completedwith the mappingof the Bafing area in Mali towards the end of the year. The epidemiological mapping of the southern extension area was also completed. In both areas detailed mapping was also carried out which involved more than 490 villages. Extensive surveys were carried out in the original OCP area in which over 130 villages were evaluated. With regard to ophthalmological activities the emphasis was mainly in the western extension area. Collection of base line data for the evaluation of the long term effect of ivermectin mass treatment on the population was carried out in the Sankarani river basin in Guinea. Seven more villages in the southern and eastern Sierra l-eone were examined to determine the extent of blinding onchocerciasis in Sierra lrone. In the Upper Niger Basin in Guinea a survey was undertaken to enable decision making with regard to larviciding. -4- With the completion of both the simple and detailed mapping in the programme area, communities at risk of onchocercal blindness were identified and ivermectin treatment targeted to over 1500 villages. Pre-treatment evaluation was carried out in the villages in the western extension area that had had at least one cycle of ivermectin treatment. In the effort to find a more sensitive means of diagnosis and less costly method of dif- ferentiation between blinding and less blinding onchocerciasis, nodules and sera were collected from several villages for studies in immunodiagnosis and tests assays with the DNA probe, (see 3.2). 3 OCUI,AR DISEASE PATTERNS AND PARASITE STRAINS. 3.L Ocular disease patterns in the OCP Three distinct ocular disease patterns have been described in the OCP which differ in their severity with regard to the associated community pattern of onchocercal ocular disease and blindness. These are: i. -the severely blinding onchocerciasis, found usually in the savanna areas where the vector for transmission is the savannavector S. damnosutn.r.s. and/orS. sirbanum.The associated ocular disease pattern is characterized by a linear relationship between onchocercal eye disease as well as blindness and the CMFL. ii. -mildly blindingl onchocerciasis found usually in the forest where S. yaherue or S. sanctipauli is the vector. Onchocercal blindness rates do not increase with increasing CMFI. sclerosing keratitis is usually absent, and the frequency of occurrence of the other onchocercal eye lesions is low. iii.-Sierra kone onchocerciasis found in south Sierra Irone and transmitted by the vector S. soubrerue B. The prevalence of onchocercal blindness increases with increasing CMFL though for a given CMFI. the prevalence is half that which obtains in the zones with severely blinding onchocerciasis. Onchocercal eye lesions also occur at a lower rate than in the zones with severely blinding onchocerciasis though the rates are somewhat higher than those found in the zones with mildly blinding onchocerciasis. I The term "mildly blinding" to describe forest onchocerciasis is introduced to replace a) the less appropriate term of "non blinding" since some blindness, though low is found in the forest and b) the now inappropriate term of "less blinding" which could well apply to Sierra l-eone oirchocerciasis wtriitr is less blinding than thE "severely blinding"'ih'the savanna although it is by no means mild. Another ionsidered term "niildly path"ogenic", describes the siiuation lir the forest, but it introduces a pathological conc,lpi to contrast a clinical description of "severely blindin$t - -5 - It is believed that these specific community patterns of ocular onchocerciasis are asso- ciated with differert O.volvulru strains with different levels of pathogenicity present in the various geographical areas. 32 DNA Probes for differentiating Forest and Savanna Strains. In an attempt to test the hypothesis mentioned above, 300 nodules collected from 98 individuals residing in ll villages in which the ocular disease pattern was well established as either severely blinding or mildly blinding were coded and sent to Dr Unnasch in the University of Alabama. 130 Nodules from 55 individuals from 6 villages in Sierra Leone, were also included. Samples of adult worms were analyzed on the basis of hybridization to the strain specific probes pFS-1 and pSS-1BT. pFS-1 and pSS-1BT are both members of a highly repeated DNA sequence family with a unit length of 150 base pairs (bp).As a first step in the analysis, the 150bp family was amplified from each sample, using the polymerase chain reaction (PCR). The PCR amplification products were then classified on the basis of their ability to hybridize to the strain specific DNA probes. A strong correlation was noted between the DNA probe classification and the severity of the disease, (Fig.1a). The results support the hypothesis of a strain association with ocular pathogenicity. In addition, the results demonstrate that the DNA probes are able to predict the pathogenic potentiat of a given parasite population in large parts of West Africa including the forest/savanna interface in the cdte d'Ivoire. The DNA probe results characterized isolates from Sierra Irone as a mixture of severely blinding and less pathogenic parasites, (Fig.1b). These results suggest that a mixture of severely blinding and mildly blinding parasites may be endemic in Sierra lrone, or that a hybrid form of the parasite exists in this region. Further work is needed to distinguish these possibilities. Further work has demonstrated that the 150bp repeat family may be successfully amplified from all diagnostically important life cycle stages of the parasite. Character- ization of the amplified products by hybridization to the strain specific DNA probes has also been adapted for use with non-radioactive detection methods. With the development of an assay to distinguish severely blinding and mildly blinding strains of the parasite it is therefore possible to utilize this technology in laboratories within the OCP. 3.3 Further studies and operational apptications of DNA probes. Dr Unnasch will undertake in depth studies of onchocerciasis in Sierra Irone, in an attempt to determine how it differs from the classical mildly blinding forest onchocerciasis and the severely blinding savanna type. These studies will include DNA sequencing using specimens already collected. Additional studies will be conducted on isolates from three selected villages, Bonjeima in the south and Yisaia and Kambia in the north of Sierra i a)I Severely bliDdhg onchoccrcisia [---l xildy blinding oacbcerciuis [-eone. In this connection nodules will be collected from persons in the last 2 villages and blood samples will be taken at the same time for other studies. Fig. 1: DNA probe classification of O.volvulus 90 80 o 670 o o -60 o q.r 5O a0 c+0 q) C) bsop. 20 100 10 0 100 90 60 Forest Undecided Savanna o q) ?zo o a -60 o o50 bo6 tr40 o C) o30 20 10 0 Forest Undecided Savanna Furthermore, Dr Unnasch will characterize specimens from nodules to be collected from upper Sassandra in Guinea using the DNAprobe. He will also try to identify the type of L3s from flies preserved in alcohol, collected from the northern part of the western extension and Sierra Irone. A proposal was formulated for the establishment of an OCP laboratory for DNA probe work. An OCP scientist is to be trained in O. volvulru strain differentiation technology in Dr Unnasch's laboratory at the University of Alabama in Birmingham. This proposal i + b) Jierra l2one -6- 7- the characterization of the O. volvulus strain in the S. squarnosum areain the East and identification of I3's collected in post control studies. - the estimation of the proportion of animal filariae in the ATP's in selected areas including the northern part of the western extension. - the investigationi of the distribution of O. volvuhts strains between the forest and savanna areas in C6te d'Ivoire in particular. At present the DNA probe can be used to detect infection in single flies. It is hoped that in future the probe will be applicable to determine the level of infection in a collection of large numbers of flies in areas where larviciding has been stopped. 4 TVERMECTIN During 1990, ivermectin was distributed actively by OCP in l7l?vtllages with a population of 255,485 and at an average coverage of 64Vo. Altogether, over 280,000 individuats were treated both actively and passively in the entire OCP. Most of the people treated were in the western extension as set out below. The Lunsar Eye Hospital, a Non-Governmental Organization (NGO) in Sierra Leone treated over 75,000 people both actively and passively. Table 1: Distribution of ivermectin in the Western Extension Country Population No. treated Vo coverage Sierra lrone Guinea Mali Senegal Guinea Bissau 45726 67573 55954 75604 18329 31983 42694 34709 9203 10272 69.9 63.2 62.0 59.0 56.0 Total 203126 128861 63.4 4.1 Ivermectin distribution in the Western Extension In the last year 244,120 ivermectin tablets were distributed in all the areas at risk of onchocercal blindness in the 5 countries of the Western extension except in the river basins of the Bafing in Mali, Seli, Pampana and Bagbe in Sierra Irone, and Bafing and Bakoye in Guinea where detailed mapping had not been completed. Of the total population of203,126in 1,464villages, 1.64,426,(8LVo)were actuallypresent inthevillages at the time of the distribution and L28,861, ($.a%) were treated, (Table 1). In the 36 hour monitoring period, only minor side reactions were reported in some villages treated s .t .,*,*rI -8- for the first time. The activities were carried out by 234 national technicians supported by 54 OCP technicians. Fig. 2 Changes after three rounds of ivermectin treatment in Asubende 0) 6 (,) (! q) L I q) ,<a o o)b!6 q.) oL a a(6 t< q) ,D 6 O z '; 70 o d60 .:lq r. 5oq) q40 v30 6- e0 >, 'Boq) :?o o i60 Eto u40 ,< o 'i 30 q) 5zo 10 -aO 100 90 BO 20 10 0 100 o 10 20 30 Number of rnonths after first treatment 40 4.2 Southern Extension and reinvasion areas. In the southern extension, ivermectin distribution was carried out in 3 river basins of Asubende (Pru), the Mono and the Oueme. The average coverage for these areas was 62.3Vo. In the reinvasion zones and some of the less well controlled areas, nearly 14,000 people received ivermectin with a coverage of around 61Vo. T a ., , -.".J lst treatment (") Skin mf load + I I + 2nd treatrnent 3rd treatment 4thtre atrnent (b) Ocular mf load 94.3 Adverse reactions Adverse reactions have been minimal. The only severe adverse reactions reported by OCPwere 2 cases of asthmatic attacks in known asthmatic individuals, one occurring 24 hours and the other the third day after treatment. The Lunsar Eye Hospital in Sierra I-eone reported one case of optic neuritis following ivermectin treatment. 4.4 Microfilarial reduction and repopulation. A reduction of skin microfilarial load of 98.2%was observed again two months after the third annual large-scale treatment with ivermectin in Asubende, (Fig. 2a). Skin microfilarial repopulation occurred 4 to 12 months after treatment and reached levels which were similar to the levels recorded in the previous years. The effect of ivermectin on persons treated three times is therefore not different from that observe d after Zannual treatments and the speed of repopulation after each treatment appears similar. 4.5 Effect on ocular Onchocerciasis. The results of the examination carried out 3 years after the start of the community treatment with ivermectin in Asubende show that among some 300 people who have had regular annual treatment, ocular microfilarial loads have decreased to very low levels,(Fig.2b). In this group, eye lesions of the anterior segment show regression. Sclerosing keratitis, even at the advanced stage of development, show ."g...ri,o1 and iridocyclitii no longer occurs. I-esions of the posterior segment of the "y" hur" remained stable intheir development. These changes in the eye lesions of the population are comparable to what has been described as changes which occurred after iome 10 years of vector control. The benefit is even greater because posterior segment lesions have remained stable in their development, unlike the situation with vector control during which some posterior segment lesions continued to progress. It is quite evident that annual ivermectin mass treatment is adequate to control onchocercal morbidity. Because of the small number of individuals involved, it has not been possible to demonstrate at this stage what effect is to be expected in those who take ivermectin irregularly. I-org term follow up is therefore necessary. 4,6 Effect on transmission. Though studies to determine the effect of large-scale ivermectin treatment on trans- mission has been concluded, there was an opportunity to draw an indirect inference on the effect of ivermectin on transmission in 1990. Suspension of larviciding for 1 month in September 1990 to test the effect of a new insecticide on both simulium and aquatic fauna in the study area of Asubende resulted temporarily in high vector densities and extremely high infectivity levels (fig.3). The period of suspension was too short for the vector population to stabilize, as was reflected by the parous rate which remained above 90Vo, and the results are therefore not directly comparable with the entomological J 10 findings of the three preceding years. Nevertheless, the very high infectivity levels L year after the third round of large-scale ivermectin treatment is further evidence for the conclusion already arrived at from the previous studies that the effect of ivermectin treatment on transmission is limited. Fig. 3: Ivermectin and transmission in Asubende Ctranges after three rounde of treatment Historical data B?/BB BB/89 89/90 Sept 90 4,7 Passive ivermectin treatment Nearly 50Vo ofsome 218 medical centres identified in the western extension carried out ivermectin distribution in 1990. In Mali all 93 health posts selected carried out ivermectin treatment in 11,700 patients. The activity was carried out entirely by the national health service. Interested NGO's notably OPC and Sight Savers have not yet started their activities. In Sierra lrone the Lunsar hospital supported by an NGO treated 29,650 patients passively.In Guinea,78 health posts supported by numerous NGO's have been opened which have treated 10,053 patients. In Senegal, only 6 of the selected 33 centres are operational and have treated 1,037 patients, whilst in Guinea Bissau, none of the 1.4 centres opened has as yet started gMng out treatment. In all, over 52,000 patients have been treated passively. In the eastern operational area, passive treatment with ivermectin was carried out only in Burkina Faso in 6 provinces. A total of 19,500 ivermectin tablets were provided for their use. o oL6 o o L C)a caJ o dz 200 t80 160 t40 120 100 80 60 40 20 0 I .*s lst treatment + 3rd treatment 4th treatmentf SepVoct. llrlllillJllilllllll No". to Febr. 2nd treatment 11 Itwas noted that therewas a need for feed-back on the passive treatmentwith ivermectin. Concern was also expressed on the effect of passive ivermectin distribution on the epidemiological evaluation of indicatorvillages in the central areawhere decision to stop larviciding is to be made.It was recommended that a small working group be formed to investigate to what extent such passive ivermectin distribution could affect the results of such evaluations. A question on the progress of the studies, on the impact of ivermectin, given several times in a year on transmission, as requested by EAC during its last meeting, was raised. Two foci had been identified for the studies: 1) Rio Corubal basin where, because of the low endemicity of infection, the effect of ivermectin could be easily demonstrated. Ivermectin was to be distributed three times in a year. 2) The Mako focus in Senegal which has ample precontrol data. Here bi-annual dis- tribution was envisaged. Discussions on the issue revealed that entomological evaluation of the studies could not be carried out because there were no longer VCU activities in the northern part of the western extension. Furthermore, entomological evaluation in the Mako focus would also be ineffective since a high prevalence of animal [3 larvae in the flies in this focus would prevent the correct estimate of transmission. It was therefore agreed that the only evaluation possible would be epidemiological. This will be carried out, after 5 - l0years of ivermectin distribution according to the protocol, using the measure of incidence in the younger age group. With regard to Guinea Bissau, it might be difficult to carry out 3 ivermectin distributions per year because they will have to be restricted to the period from November to middle ofJune to avoid the rains and farm work. The meeting therefore recorlmended the studies to be carried out in the Mako focus and to conduct a feasibility study of carrying out the one in Guinea Bissau in the planned manner. 5 MODELLING 5.1 Priorities. Asummaryof recentmodellingapplications andplans forfuturemodellingwaspresented to the meeting. Priorities for the near future are the parameters for early detection of recrudescence, the potential of ivermectin to control recrudescence, and the implications of human and fly migration for the risk and dynamics of recrudescence. 5.2 Sensitivity analysis of the risk and control of recrudescence During the last year, the model has been used extensively to study questions related to the recrudescence of onchocerciasis in areas that had been under vector control for a : .I -12- given period of time. The study had focussed on the operational definition of recrudes- cence, its timely detection and the potential of control by ivermectin treatment. The working definition of recrudescence used was "renewed transmission and the subsequent build-up of the prevalence and intensity of infection to near pre-control levels if no intervention is undertaken". Model simulations have shown that, dependent on coverage, duration of treatment, and treatment frequency, ivermectin can prevent further recrudescence. However, the success of using ivermectin treatment for this purpose, can no longer be guaranteed when the treatment campaign starts (too) long after the start of recrudescence. A major problem in early detection of recrudescence is that the level of infection as measured by the prevalence of mf will initially be low. Moreover, model simulations indicate that the dynamics of recrudescence - the time involved in reaching significant infection'levels - can be very different even between villages with comparable pre-control endemicity and vector control history. The most appropriate strategy for post-larviciding surveillance will be based on longi- tudinal surveys at regular intervals in villages at high risk locations. A systematic series of model simulations is being undertaken to study the required interval between surveys and the threshold values for different epidemiological indicators which would indicate that ivermectin based recrudescence control should be started. q 150 140 '130 120 110 100 90 80 Fig.4 Detection ond control of recrudescence trotegy with bi-qnnuol surveys ond threshold of 3% mf prevolence in odult 60 50 40 30 20 10 0 4 6 8 10 12 14 16 Yeors since cessotion of vector control OO t.) o :l o U' c o .F o l E '6 o Lz o2 I ..!- o lvermectin treotment ongoing Treotment unneccessory Treotment too lote 18 20 13 Several simulationexamples of this longitudinal approachwere presentedto the meeting. These examples were based on an epidemiological situation similar to that of the holo-endemicvillage of Tiercoura (pre-control CMFL=70 mf/s). For this situation 300 simulations were carried out of a vector control period which was interrupted prema- turely. Because of this pre-mature interruption, 100 out of 300 simulations (33Vo) showed recrudescence. Fig. 4 gives for these 300 simulations the results of a surveillance strategy with epide- miological surveys at two-year intervals, starting three years after cessation of larviciding. In this particular strategy ivermectin based recrudescence control is started as soon as the cumulative percentage of infection among adults (excluding those who were still skin snip positive when larviciding was ceased) exceeds 3Vo.lnthis example it is assumed that the ivermectin campaign will last for L5 years, using an annual treatment schedule and ..achieving a coverage of 65Vo. Fig.5 Detection ond control of recrudescence Strotegy with 3 surveys ond threshold of 2% mf prevolence in odult 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 o Oo r/) o :l o a C o o :l E a o Lz o2 4 6 8 10 12 14 16 Yeors since cessotion of vector control 18 20 The solid line in Fig. 4 shows the number of simulations out of the total of 300 where the threshold has been exceeded and ivermectin treatment has started. Since gradually all recrudescence situations will exceed the threshold of 3Vo, after the last survey in the example (18 years after stopping larviciding) 95 out of the 100 recrudescence cases have been detected and treatment has started. In some simulations of this example the cumulative percentage of infected adults exceeded the3Vo at a given instant, even though recrudescence did not actually occur. Also in these situations ivermectin treatment will be started and in the figure these 'false positive' simulations are denoted as 'Treated r lvermec tin treotment t Treoted unnecessorily o Treoted too lote 1,4 unnecessarily'. More serious are situations where recrudescence is detected too late to be successfully controlled by ivermectin treatment and simulations with such an outcome are labelled as'Treated too late'. Fig.5 shows a second example. Here, the threshold is loweredto2Vo,which favours the early detection of recrudescence (solid line rises rapidly), but at the same time increases the number of situations where treatment is started unnecessarily. Another difference with the previous example is that only three post-larviciding surveys are carried out at 3, 7, and 18 years after cessation of vector control. This strategy is clearly unacceptable as is shown by the considerable number of simulations where ivermectin treatment comes too late. The meeting considered the above approach to the study of surveillance strategies highly relevant. The investigators were encouraged to complete the work as soon as possible -and to submit as reportbefore the EAC inJune 1991. The furtherwork should concentrate on the analysis of realistic schedules and treatment coverage, and the use of alternative indices to detect recrudescence (e.g. incidence between successive surveys rather than the index used in the examples). 5.3 Ocular disease modelling The meeting was also informed about the progress made in the development of a sub- model, describing the incidence and progression of ocular disease and the effects of control. The objective of the submodel is to provide the basis for the simulation of onchocercal eye lesions and blindness to allow the prediction of changes in these para- meters that may occur with an intervention such as large-scale ivermectin treatment. The conceptual framework for the model was formulated during a workshop organized by the Rotterdam University and OCP in September 1989. The most important parameters, variables and mechanisms were identified during this meeting. The framework has been further elaborated and a formal description of the model was made and sent to OCP for comments. During the second half of 1990 the model was actually programmed and implemented in the existing ONCHOSIM model. Apreliminary attempt has been made to quantify the parameters of the model on the basis of ophthalmological data of OCP, mainly from the Asubende focus. With the model, age- and sex-specific tables can be calculated for ocular microfilarial counts and the two groups of lesions (anterior and posterior) subdivided into early and advanced stages of development. 5.4 Additional work The meeting commended the remarkable work on recrudescence that has been achieved by the collaboration with the University of Rotterdam. It was recommended that the following additional work should be pursued: .,J 15 1. The quantification of the effect of ivermectin (both on individual and on population level) should be improved, using data of all treatments done in Asubende and in other places. 2. Since initially, decisions will be made on the basis of skin-snip counts, the variability in these counts should be carefully investigated and modelted. Also the possible benefits to be derived from adopting a more sensitive diagnosis using the skin snip method and selective groups (high- risk groups) should be investigated. 3. A start should be made to model the potential advantages of immunodiagnostic tools for the early detection of infection. 4. The highest priority should be given to the study of surveillance strategies as discussed under section 5.2. 6 ORIGINAL OCP AREA After 15 years of larviciding in the greater part of the Original OCP area, it is expected that further decisions towards the stopping of larviciding would be made. On the other hand, it is of utmost importance that the avoidance of recrudescence is ensured. The meeting therefore reviewed the entomological results in areas where larviciding was stopped last year. This reviewwas to assist in the management of cessation of larviciding in other areas. 6.1 Acceptable vector infectivity levels after cessation of larviciding In order to develop criteria for the interpretation of the entomological evaluation data to be collected in selected catching points after the cessation of larviciding , alargenumber of simulations were done to determine which vector infectivity levels could still be con- sidered to be acceptable and which levels would signal an unacceptable level of trans- mission. Preliminary simulations undertaken in June 1990 indicated that the level of vector infectivity would be unacceptably high when it would exceed 0.8Vo - l.3Vo of the pre-control levels in holo-endemic foci, and this conclusion was confirmed by a more extensive series of simulations undertaken recentty. Assuming an ATP/ABR ratio of 7Vo 'l0Vo, a parous rate of.40Vo - 60Vo and an average of 1.5 I3 in the head per infective fly during the post-larviciding period, the above level translates in an operational threshold of I to 2 flies with 13 in the head per 1000 parous flies. This threshold has been used to develop decision charts for the sequential analysis of the entomological data which would enable immediate decision making to restart larviciding as soon as the threshold values are exceeded. The charts have been used during 1990 and proved to be very valuable. There was some discussion on possible differences between the statistical approach used and other uses of sequential analysis in biometry, and this will be further investigated. The meeting recorrmended that the decision charrs, possibly after some refinement, continue to be used for the same purpose during 1991. -16- 62 Latest Entomological results The results from nine sites, (Map 2), selected for studies to assess the correctness of stopping larviciding in a number of areas in the original OCP were presented to the meeting. Large numbers of flies (minimum of 15,000 parous flies for statistically valid estimate) caught over 3 - 4 month period were dissected to look for head I3 larvae. Graphical analysis as described, (6.1), was applied to the data collected from the dis- section to assess the level of infectiviry. The results of the graphical analysis of the data collected are shown in the table2.The safety level at Nabere (Fig.6) is judged to be very good but only fair at Porga. Treatment resumed along Banifing IV (Konina Fig.7) where unacceptable levels of infectivity were found. No studies could be carried out in Karfiguela on the upper Comoe, [.oumana on the Tiao and at Fourkoura on the eastern Ilraba (not shown on the map) because of small numbers of flies. However, analysis of weekly entomological data from L2 other points suggest that the situation in the upper Como6 and the kraba at Grechan is good, and excellent at Farako. No more studies are planned for Nabere because of the excellent results but studies will be carried out in Zambo. Table 2: Post-control studies (1990) River basin Catching Point No.of No.of parous flies flies dis- with head L3 sected larvae Outcome White Volta Bougouriba Red Volta Red Volta Upper Comoe White Volta Oti Loaba Nab616 ZiouZabr6, Nangodi Folonzo Zongoiri-rapids Porga 110 18,991 4,757 13,421 1,581 8,r42 3,600 Few flies Very good Good Good Good Fair Fair 0 8 2 7 0 t6 7 Furthermore the studies will be repeated in Ziou-Zabre, Nangodi, [-oaba Zongolki-rapids and Porga. Studies will also be undertaken in Karfieguela, Loumana and Fourkoura if fly quantities permit. Other points will be chosen before the next season and will take EPI results into account. Disgection moy bc stopped < I I3IL/IOOO puous 70 60 ofa ,t !650 o !lo o q) t30 k OD 420z -17 - Vector infectivity after cessation of vector control Fig. 6: Nab€r6 (Bougouriba) .luty fSSO - Feb. l99t 4000 6000 8000 10000 12000 1,t000 16000 18000 20ooo 22000 24ooo Number of parous flies dissected Fig. 7: Konina Bac (Banifing IV) June 1990 - March 1991 1 000 2000 l0 0 20 o ar) (! q) F th o o li o .o z 18 't6 14 12 't0 I 6 4 2 0 0 Number of parous flies dissected 3000 4000 EI * .,-l -18- 6.3 Latest EPI results. The meeting was informed that epidemiological evaluation was going on in river basins which were to be considered for stopping larviciding. These were the White Bandama, the Bougouriba, the Sissili, the White Volta and the Banifing IV. The results from these surveys will be available in early April. These will be discussed with the vCU to assist in deciding where larviciding will be intemrpted. Meanwhile surveys carried out in villages on the Niger basin in Niger, where larviciding has been stopped for the last 3 years showed excellent results, except for Bangou-Koare where the prevalence was 7.ZVo. This was however a drop from the previous years' of ZL.1'Vo.The general trend in this village is aprogressive decrease in prevalence over time, although at a slower rate than the predicted trends. 6.4 Epidemiological Importance of Infected Migrants. Migration studies were included in the parasitological surveys conducted in the river valleys in the central OCP area a) to determine whether human migration does occur from zones unprotected from human onchocerciasis, particularly the south of COte d'I- voire to the protected parts of the central OCP area and b) to what extent this occurs. The specific aim of the migration studies was to assess the contribution of migrants to the prevalence and intensity of infection in villages from 5 major river valleys (See Map 3) and their potential role in causing relapse of transmission. In the 41 villages on the Irraba, Comoe, Bougouriba and the White Volta river valleys in Burkina Faso, the migrant population varied from 0.0Vo to l8.LVo of the village population with an average of 4.9Vo. Villages on the Black Volta in Ghana and Cdte d'Ivoire had a migrant population of 0.6Vo. The prevalence of infection in the migrants of 8.2Vo was significantly higher than that for the non-migrant population (l.l.Vo). Migrants with more than 16 microfilariae per skin snip was 1..5Vo as against 0.2Vo in non-migrants. Nearly all the infected migrants came from the south of C6te d'Ivoire. The epidemiological importance of this phenomenon is limited because of the very small number of infected migrants per village, besides two-thirds of the infected migrants came from the forest zone of C6te d'Ivoire and are believed to be infected with the less pathogenic forest strain. Because of the geographical variations of migration patterns, similar studies will have to be done at other river basins for example in the Banifing IV where such studies will be carried out in 1991. In view of the potential epidemiological importance of migration, it was recommended that such studies should continue and should incorporate particularly new settlements in the controlled areas. ,',+ l9 6.5 Plan for cessation of larviciding in 1991.. Cessation of larviciding will be considered in the river basins of the white Bandama down to the Bou confluence, Banifing IV, lower Bougouriba and the White Volta benveen its confluence with the Sissili through to the Morogo. Results of EPI surveys planned for theseareaswill beavailable earlyApril. Atthattime the decisionas towhetherlarviciding should stop in those river basins will be made (see 6.3). However, White Bandama basin having been reinvaded until L984, especially the Bou, it is unlikely that treatments will be completely suspended in 1991. In the Banifing IV, vector infectivity levels recorded in 1990 after cessation of larviciding was unacceptably high. This river will be treated in 1991. Limited suspensionwill be undertaken in order to collect infective larvae for DNA identification. 7 DIAGNOSTIC TOOLS 7,1 Immunodiagnosis: update and plans. A summary of the recent progress in the development and testing of immunodiagnostic tools for the early detection of new infections following the Heidelberg meeting of November 1989 was given. At the first round of a TDR funded multi-centre study which involved the blinded testing of the recombinant antigens from different laboratories, sera from 26 patients with patent onchocerciasis infection and other sera,24 of which were cases with patent W. bancrofti infection were used. The sensitivity of each of the recombinant antigens was low, but a combination of four of the antigens would have given a positive test result in24 of. the 26 onchocerciasis patients, and in only one of the 24 W. bancrofti sera. After the first round of testing a recommendation for the devel- opment of an antigen cocktail of the most promising antigens was made. The second round of testing will soon start and will involve mainly sera collected in the OCP. [t concerns sera from indicator villages in the R. Koulpeolgo valley where there has been complete interruption of transmission for 15 years. These witl be used to study the importance of residual antibodies in those above 15 years who were infected previ- ously according to historical skin snip information, while those below L5 years would form a group of endemic controls. Sera have also been collected in November 1989 and November 1990 from 137 initially skin snip negative persons from the Pendie areawhere there has been a relapse of transmissiog particularly during the rainy season of 1988. Of the 137 persons,30 became skin snip positive around the time of the first serum collection and 14 others between the two collections. These sera are unique as they provide longitudinal information on new infections. There are no other areas in the OCP where such sera can be collected, and the meeting agreed that if more sera on incident cases are required, these are to be collected in areas with high levels of transmission outside the Programme area, possibly in the Cameroon. However, in the case of a serious breakdown in vector control, longitudinal sera will be collected from a cohort of initially skin snip negative individuals. mThe meeting wuls very satisfied with the progress made, the remarkable collaboration benreen the different laboratories and the important contributions made by TDR/FIL. It was strongly recorlmended that the Programme continues to collaborate closety with the immunodiagnosis subgroup of the SC/FIL and tries to maintain the momentum in this field. Nevertheless, it was agreed that untit there was solid evidence that immuno- diagnosis is avalid alternative, the planning for surveillance under devolution should be based on the assumption that this will be done with the classical skin snip technique. It was agreed that the first priority of the OCP was an immunodiagnostic tool for the early detection of recrudescence. 72 Community Diagnosis using nodules palpation. Community diagnosis of onchocerciasis using skin snip is invasive, r&y carry a risk of HIV infection and involves special skill. There is therefore a need for a simple non-in- vasive technique. Prevalence of nodules is reputed to correlate with prevalence of onchocerciasis infection. OCP therefore undertook a re-analysis of historical data of nodule examination to assess the relationship between nodule load and the CMFL. Fig. 8: Mean number of nodules and CMFL Rc.ult! lor totel ville3e populrtion 20 80 r00 CMFL There was quite a good correlation between the mean nodule load and the CMFL (Fig 8). The prevalence of nodules in the total population showed a regular increase till a CMFL of about 30 mf/s and a levelling off thereafter, (Fig 9). The results suggest that a CMFL of 10 mf/s corresponds approximately to a prevalence of body nodules of ZlVoin the total populatioq an arithmetic mean number of nodules of 0.4 nodules per person c oo q, A q, A oq) ! o €, D6o C'A o lrq, D 6 q) I 3.5 3 2.5 2 .5 0.5 0 0 6040 It a T ! ir !I a I r I a !a ! I a ! f. l1 lt nn B 2t and a geometric mean of 0.25 to 0.3 nodules per person. Using data for adult males only, the variability increases significantly (smaller sample size) but at CMFL of 10 mf/s the corresponding prevalence wu 40Vo to 50Vo, with an arithmetic mean and a geometric mean of 0.8 to L and 0.4 to 0.8 nodules per adult male respectively. Fig. 9: Prevalenee ol body nodulee and CMFL Rcrultr lor rll r3c aroupr coBbinGd 20 00 100 CMFL r00 9o E o60 c tE?0 ! .3 60 ID E506r t.0 (, o !306 o&ao lo 0 o 60t0 These results are promising and suggest that nodule palpation may provide an alternative non- invasive method for community diagnosis. Observer variation may play a significant role in the identification and counting of onchocercal nodules in lower level personnel, and special studies have been planned to assess this. 7,3 New Methods for evaluation of control At present the evaluation of vector control is based on the analysis of trends in the prevalence surveys and the intensity of infection. In the areas where vector control is the only means of interventioq these measures are quite adequate after 5-8 years of control. However, in areas where vector control and ivermectin treatment are being carried out at the same time i.e. in the extension areas, the use of the present epidemiological indicators to evaluate transmission will no longer be valid. There is therefore a clear need for better tools for the epidemiological evaluation of interruption of transmission as a result of vector control in the extension areas where the evaluation is compromised by concomitant ivermectin treatment. One approach might be to measure the incidence of infection in a) cohorts of skin snip negatives who would not be treated with ivermectin until proven infected and b) children born after the start of intervention. However, lt I aI a I Ifr I T lt ra I a ril T a1l I E tr T It rl 22 Previous experience has shown that such incidence measures have a very low sensitivity during the first 5-10 years of control. More valuable would be an immunodiagnostic tool to detect superinfection in that part of the population which has the highest exposure. In this respect, the recent advances in the immunodiagnosis of onchocerciasis may prove to be very important. (see 7.1). The meeting recommended that the method of longitudinal follow-up in cohorts of skin snip negatives and children born after the start of the intervention should be instituted to measure the impact of vector control. 8 BRIEFING ON INTRA.I.'NIT RESEARCH ACTTVITIES. E.l Insecticide research. Several lots of samples of B.t.H14 from Solvay were tested; the latest [ots, produced by industrial techniques, are equivalent to or slightly better than the current operational formulations. Abbott has set up a new bioassay system for B.t.H14 which will be tested by IRU/OCP later in 1991. Arrangements are being made with Institut Pasteur (Dr. A. Delecluze), for testing on S. damnosum, B.t.H1.4 that were engineered for producing individually the toxins found in standard strains. This could identify the relative importance of these toxins for black fly control. Most river tests in 1990 was in connection with the selection of an adequate phoxim formulation as a replacement for chlorphoxim. The S|VoEC commercial formulation from Bayer was preferred to the experimental2iVoEC and 4IVoEC formulations. The operational dosage is presently set at 0.16L of formulation per -3/r for the 50EC formulation. Other river tests were done with a new formulation of carbosulfan, the evaluation of which will continue in 1991. Six new insecticides were screened in 1990. OMS 3052 (OP by Bayer) had too little activiry, and was rejected. OMS 3051 (pyrethroid, Bayer) was extremely active, and tests will be performed on non-target fauna to assess its selectivity. OMS 3050 (pyrethroid, ICI) is under evaluation. Initially with low activity some aged solutions showed high activity; this phenomenon will be further investigated. Three formulations of OMS 3055 (new group of insecticides, Hoechst) are being evaluated; they are less active than permethrin, but their selectivity remains to be assessed. Following the discussions of the 1991 Ecological Group Meeting, it was decided that a re-evaluation of pyrethroids should be performed with the objective of identiSing compounds that would be more selective forS. damnosunt than permethrin; this would help fill the gap found in the options for larviciding at dis- charges benreen 15 and 70m3/s. Other projects at IRU involve further standardization and improvement of bioassay protocols and data analysis, with particular stress being put on resistance detection. i 23 82 Ecologicalmonitoring The meeting was briefed on the salient points which emanated from the meeting of the Ecological Group. It was informed that the Ecological Group reviewed the report of the hydrobiologistswhich dealtwith aquatic monitoring activities in relation to the selection of new larvicides and routine monitoring of watercourses under larviciding. The Ecological Group observed that long-term monitoring of data with respect to drift (the totality of the organisms and the debris carried in water) have not clearly revealed any impact due to larviciding. Studies would therefore concentrate on a small number of monitoring sites to collect as much quantitative data as possible on the different substrates and biotopes. As regards "recolonization", studies would be performed on the IJraba and the Nazinon with respect to refuge zones to enable discussions to be started during the next meeting of the Ecological Group. In connection with access to and analysis of the data on aquatic monitoring, the Ecological Group recommended that the data at Salford should be transferred to Ouagadougou and manageable programmes be made available to aid in the analysis. As regards training, hydrobiologists were to be provided with simple statistical aids to facilitate data collection and analysis. Furthermo re, a2-day training workshop should be organized alongside their 1992 annual meeting. After analyzing the different larviciding tactics, which bring into play the six OCP operational larvicides, it emerged that only organophosphorus compounds with all their risks of resistance were used in water discharges of 15 to ,5 ^3 /sec. The Group therefore recommended the search for larvicides belonging to other chemical families mainly pyrethroids and carbamates. They remarked that the problem and significance of insecticide resistance amongst aquatic non-target organism was being studied. 8.3 Update on Cytotaxonomy data Five main species of the vector S. damnosun complexiz S.squamosum; S.yahense; S. damnosum..s.s.; S.sl'rbanum and S.sozbrerue (Beffa form) now exist in the eastern oper- ational zone. A sixth species S. sanctipauli (Djodji form) disappeared after the start of larviciding in 1988. Two forms of. S.damnosutn.r..r. are now known to exist in the EOA: the Nile and the Volta form. S. sirbanum exists also in two forms in the EOA The n*ro are rytota(onomically differentiated from one another by the presence or absence of the characteristic Y-lined (tS3) heterozygous inversion of the male individuals. Populations possessing the IS-3 inversion are the polymorphic form (the former S. sudanerce of. Vajime and Dunbar, 1975) and are the most predominant in the southern half of the OCP area. The northern j -24 - Population or the monomorphic form lacks the IS-3 inversion. This is the type named after River Sirba in Niger. In the western operational area, 9 main species exist. They are S. damnosurn s.s., S. sirbanum, S. diegererue, S. yahense, S. sEtarnosum, S. soubrerue (menankaya form); S. konkourense, S. sanctipauli s.s and S. soubrerue B. 'The chutes Milo" form of S. soubrerue has disappeared from records since 1988 after the second round of anti re-invasion treatments in Guinea. It was observed that cytotaxonomy data in the Prograrnme area was being compiled. A stage has now been reached when data from both the west and the east will be linked up and upgraded every few months. This will attow geographic as well as time analysis of information. E.4 Identilication of adults vectors and I3 head Larvae Identification of adult vectors by means of morphology and morphometry is now an operational activity in ocP. With these techniques, it is possible to separate savanna from forest vectors among which S. yahensef S. squamosum and S. sanctipauli s.L groups can also be separated with a high degree of confidence. Research in morphometry and electrophoresis is presently in progress to enable further separation of the different species of S. damnosum complex and to improve the reliability of identification criteria. Besides, morphometry can be applied to I3 head larvae to separate O. volvulw from other onchocerca species except O. ochengl Using this technique and DNA probes, it will be possible to differenciate O. volvulus from other onchocerca species and to follow up closely the role of the different members of the S. damnosun complex in the trans- mission of the disease in different foci. This knowledge will be most useful in the planning of vector control operations. 8.5 Hydrology The meeting was informed of the remarkable improvement in the techniques and equipment at the disposal of the hydrological brigades of the VCU. Teletransmission of hydrological data is being used extensively whilst data analysis using special computer programmes allows regular upgrading and availability of information to optimize the use of insecticide during larviciding. i _-** ?s 9 OPERATIONAL PI.ANS FOR 1991. 9.1 Westem extensions. In Guineq full scale vector control of the upper Sassandra, Sankarani, Milo, and Niandan will be pursued. Coverage could be reduced latter on in the basins where O. volvulus could be identified as the mildly blinding type. The lower part of these basins as well as the basin of Mafou, Niger and Tinkisso will be routinely treated. In Sierra lrone, the classical method of vector control does not allow an effective control of transmission because of the very high vectorial capacity of. S. soubrerue B. An attempt will be made to eradicate this species which is restricted to the main rivers in southern part of the country during the dry season. However, it is likely that S. soubrerue.B. from the Mano river on the border with Liberia and from Liberia itself, assisted by easterly winds, will recolonize south eastern part of Sierra Irone at the beginning of the rainy season. The northern part of Sierra Irone which is a source of re-invasion for Guinea and Mali will be routinely treated. Future strategy in Sierra I-eone will depend on the results of the attempt at eradication of S. soubrerue B. 9.2 Eastern Operational Area. Larviciding in the eastern zone in 1991 will follow largely the ptan of the previous year. As in the past it will cover all the rivers harbouring btacklly species known to be vectors of the severely blinding onchocerciasis. All the torrential rivers of the Atacora chain where S. squamosum and S. yaherue breed will also be treated. However, the treatment will be done mainly in the dry season when studies have shown these species to be most infective. Similarly, the treatment of the lower Comoe will be extended below Beti6 in order to eliminate the savanna species there. This will form part of the search for the potential source of reinvading blackfly to the lower Black Volta. IO DEVOLUTION The Coordinator of the Director's office introduced the subject by defining it as: i) the taking over of the residual activities of OCP and their integration into the national health system, ii) the application principally of epidemiological surveillance to detect very early recrudescence and iii) the containment of recrudescence by large-scale ivermectin treatment. He reported that the ninth JPC which was held in Conakry last December had noted a remarkable turning point in the progress of devolution. The plans for devolution of all the 7 participating countries in the original programme area have been accepted and an institutional framework has been created. All the participating countries 26 have integrated their residual activities of onchocerciasis control into existing pro- grammes of major communicable disease control. The plans of their activities, epide- miological surveillance and ivermectin treatment are based on 3 strategies which are active, passive and advanced. Active surveillance and large-scale ivermectin treatment witl be carried out by mobile national teams and also by NGO's cooperating with the governments. Indicator villages for the surveillance will be selected in collaboration with OCP. Each village will be surveyed every 3 years whilst the zone in question will be surveyed every year. There is a need for a more sensitive test (immunodiagnosis) to replace skin snipping which is less sensitive and less acceptable to the population. Circulation of data benreen the par- ticipating countries and OCP and between the countries themselves witl have to be encouraged. The on-going studies with the model will give guidelines as to when recrudescence occurs when the decision to institute large-scale ivermectin distribution will have to be taken. Ivermectin treatment will be annual and will last at least 15 years. Naturally these plans will be changed when a macrofilaricide becomes available. OCP will play an important role in the selection of villages, training, computer support and co-ordination. In the passive strategy, surveillance and passive treatment will be carried out by fixed health institutions which could be national, private or NGO's. Presumptive diagnosiswill form the basis for screening. An attempt wilt be made to improve the provision of iver- mectin to the institutions, registration of patients, the circulation of information and supervision. In the advanced strategy surveillance and treatment will be carried out in the satellite villages of health institutions through suchprogrammes like Maternal and Child Health, vaccinations and health education. The institutional framework of Devolution was discussed at a meering held in OCP/A- FRO on 6- 8 February 1991. A decision was taken to create a post of a coordinator of devolution, a task force on devolution and national teams to deal with the prevention and control of communicable diseases. The coordinator of devolution will be a WHO staff member and will be based in the WHO Representation in Ouagadougou. He will collaborate closely with OCP, with the participatingcountries, theWHO representatives of theparticipatingcountries, the donor countries, the United Nations Agencies, research institutions in training matters, infor- mation diffusion, research, finance etc. The task force will be composed of the Regional Advisor to AFRO on parasitic diseases, a representative from the OCCGE, the Devolution Coordinator and a representative from the OCP.Itwill beresponsible forfurnishingthe directivesfororganizingworkshops for the surveillance of diseases, assist the national WHO Coordinators in the elaboration of appropriate materials for training in the surveillance of onchocerciasis, co-ordinate .a ncountry and inter-country training activities and prepare annual report of activities by country for AFRO. The national teams for the prevention and control of diseases will be responsible for preparing each country's plan of operation on devolution activities, prepare a map of alt relevant districts showing the number of inhabitants, the medical and para-medical personnel, the infrastructures and others. The teams will prepare an inventory of the trained personnel, of supplies and equipment, a budget request and its justification for the prevention and control of diseases, organize training workshops on the national level for trainers viz district medical officers and then district health workers. They will organize activities in connection with social mobilization of the community and furnish through the WHO Representative quarterly reports on the activities on surveillance and the progress on the devolution. The meeting received the devolution plans with satisfaction and noted that devolution plans had taken a concrete and practical turn. It urged that support should be given to the plans to make it succeed. 1I DATA ANALYSIS AND COMPUTER STJPPORT Data processing and analysis are being progressively improved to help the staff in the operational decision-making. The prograrnme for summary analysis of epidemiological data requested last year has been developed and an initial system is available in all the OCP bases that have a micro-computer, and all the EPI portable micro-computers. This system has been immediately successful since it gives a quick view of the summary data on each epidemiological evaluation. Fig 10 shows a screen display of this programme for the village Folonzo. Given the limits of such an analysis, another parallel system will also be developed for a longitudinal cohort analysis. The weekly entomological data programme, to help the entomologists during their briefing, is fully operational. This system allows the VCU staff to provisionally update the database, using the information received weeklyby radio for immediate analysis and decision-making. The integration of data processing in the principal OCP bases has enabled the users to develop data-banks on cytota(onomy, morphometry, and insecticide research. An attempt to tackle questions concerning the geographical information system was also made by preparing a computerized mapping system of the OCP area. Thus, for the moment, information concerning resistance and vector distribution can be superimposed automatically on the map. The exploration of this system witl be continued to make it more flexible and also improve the presentation of the Programme's results. This fast development of data processing has led OCP to set up a data processing coordination group presided over by the CAM, with BIS being in charge of the secretariat. This will enable OCP get a two- year detailed plan for all data processing requests, including equipment, softwares and staff training. I 2A Fig 10: Computer display showing an example of the EPI summary database for the village of Folonzo. The meeting expressed its satisfaction with the vast development in data analysis and computer support. However, some participants expressed the wish to have some form of training in computer use as well as prograrnmes being made available in the French language. 12 MISCELI.ANEOUS It was noted that the OCP glossary of terrns has now been compiled and translated into french. However, work still needs to be done to improve it. In particular, the french version had to be reviewed for the appropriateness of the translation. The chief VCU was entrusted with the coordination of the review. It was also recognized that the glossary had to be constantly updated. Participants were urged to make it a point to submit such contributions two months before each yeaCs technical review meeting. The question of publications was raised. [t was noted that OCP is now publishing scientific articles regularly. It was however felt that there is a need to publish articles which should deal with the divers experience of the Programme including aerial operations, car- tography, management and cooperation with national scientist. AII members of staff are urged to produce a paper at least in their specialized field by the next meeting. i I3 Survcy Doration Pop. Pop. pop.No. Datc Typr ControI Censue Prescnt Exanincd Civc the dcsired survef oumber for further analysis (0 lor none) 32 7 EPI DATABASE SUUIIARY STSTEM Fl ag - t.66 Vi I lagcNumber Country code Basin code Phasc codc I 7305 S2 7St0 S3 79il S4 8u2 S5 8{12 S6 86t2 S7 890t S 187 286 312 33e ?79 410 4{5 l8{ 264 261 300 3{6 373 39t t8{ 262 260 267 3rs 358 358 2,0 2.2 I.3 I.S 2.2 2.5I.I l9 t l0 I Yi I lagc name Couatry name Basln Bam? . Fhase Bam? . 14.35 30.r20,81{.9 t 7.00 10.00 12.00 t{.08 t0t 0Nzo BURIINA FASO COMOE I 7S0l Nuuber of surveys Prcv. Prcv. of MFS CMFL Blind. 60 -2 7t.5 61.8 5l ,3 33 .9 t2.9 3.3 7.77 2.04 3.08 0.s6 0.08 -29 - 13 RECOMMENDATIONS 1. The large scale epidemiological testingof DNAprobes forO.volvulus strains has clearly proven that this tool has a great operational potential. A staff member of OCP is to undergo training in the technique of DNA probes and a central OCP laboratory established in order to enable the Programme apply this technique as soon as possible. 2. Furtherstudies atthe Universityof Alabama,willconcentrate onSierrakone "strains" by sequencing studies using already available worm material, and nodules to be col- Iected from 20 additional individuals in Yisaia and Kambia. 3. Because of the lack of valid entomological methods for the evaluation of O.volvulus transmission in the north-west of the Western extensiorL the proposed studies on the effect of more frequent ivermectin distribution on transmission will have to rely on classical epidemiological methods. This implies that the impact of control can only be evaluated after at least 5 years of intervention. A study in which ivermectin treatment will be given bi-annualty will be undertaken in Mako focus in Senegal. 4. A study will be done in mesoendemic communities in the Western extension to determine the validity of nodule palpation as a method for community diagnosis of onchocerciasis 5. OCP should continue to collaborate closelywith the immunodiagnosis subgroup of the filariasis steering committee of TDR in order to accelerate the development and field-testing of the antigen cocktail. In case of a breakdown of vector control such as that which occurred in Pendie, longitudinal sera should be collected from individuals who may have pre-patent infections. 6. The current approach to modelling the detection and control of recrudescence is highly relevant.Areportshould be submittedbefore the nextsessionof the EACwhich should include an operational definition of recrudescence and quantitative guidelines for recrudescence control. 7. Studies should be undertaken to try to explain the unsatisfactory entomological results for the Banifing IV following temporarycessation of larviciding. These should include renewed epidemiological surveys which should also cover possible temporary residents, e.g. fishermen. Infective flies should be stored for DNA probe analysis later. 8. Further migration studies should be undertaken focussed on new settlements and nomadic populations, for example, fishermen at high risk locations. The epidemio- logical importance of infected immigrants should be further studied in modet simu- lations using the presently available migration information as a reference. I I i *^{ 30 9. Investigations are required in parts of the central OCP area to determine to what extent passive ivermectin distribution has affected the epidemiological evaluation data required for decision making on cessation of larviciding. 10. Epidemiological evaluation of the effectiveness of vector control in interrupting transmission in the extension areas will have to rely on the assessment of incidence of infection as revealed by skin snips. This makes it necessary that individuals who are skin snip negative in indicatorvillages are not treated with ivermectin till proven infected. 11. In 1991, the eradication of. S. soubrerue.B. in Sierra lrone will be attempted during the dry season. 12. Although there has been a significant increase in the number of scientific publications by OCP staff during the last two years, a greater number of staff should make an effort to publish more articles. These should include a much wider variety of subjects such as aerial spraying equipment development and techniques, cartography, and collab- oration with national scientists and technicians. 13. It is recommended that nationals from participating countries be invited to next year's Annual Internal Technical Review meeting. i Appendix A. 1.) 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. t6. 17. 18 19. 20. 21. 22 23. 24. 25. 26. 27. 28. 29. -31 - List of participants Dr. H. Agoua (Co-rapporteur) Dr. Akpoboua Dr. O. Ba Dr. C. Back (Co-rapporteur) Dr. D.,A"T. Baldry Dr. Y. Bissan (Co-rapporteur) Dr. B. Boatin (Co-rapporteur) Dr. D.A Carvalho Dr. KY. Dadzie (Rapporteur) M. Fiasorgbor Dr. P. Guillet (Vice-chairman) M. Henderick M. P. Kabord M. V. K6r6 M. R. Meyer M. A. Plaisier, University of Rotterdam M. P. Poudiougo Dr. D. Quill6v6r6 Dr. J.H.F. Remme (Chairman) Dr. E.M. Samba Dr. Sangar6 Dr. A. S6k6t6li M. E.J. Senghor M. E. Soumbey Alley (Co-rapporteur) M. S.A. Sowah Dr. L. To6 Dr. T. Unnasch, University of Alabama M. L. Yam6ogo Mr. D.G. Zerbo .{ a-32 - Appendix B. List of recent OCP publications Agoua H., Quill6v6r6 D., Back C., Poudiougou P., Guillet P., Zerbo D.G., Henderick J.E.E., Seketeli A., Sowah S. (1990). L'evaluation des moyens de lutte contre les simulies dans le cadre du Programme OCP (Onchocerciasis Control Programme). Colloque International sur la lutte contre les insectes vecteurs de maladies, Anvers (belgique), 13 - 14 Decembre 1990. Awadzi K., Dadzie KY., De Sole G.and Remme J. (1990). Reactions to ivermectin treatment in onchocerciasis patients. Acta Iridensia Vol.59, pp. 193-200. Baker, R.H.A., Guillet P., Seketeli A., Poudiougou P., Boakye D., Wilson M., Bissan Y. ( 1990). Progress in controlling the reinvasion of wind-borne vectors into the western area of the Onchocerciasis Control Programme in West Africa. Phil. Trans. Roy. Soc. B 328.731 -750 Brown, K.R., Duke B.O.L., Ginger C.D., Gutteridge W.E., Le Berre R., Overbosch, D., Remme J., Samba E.M., van der Kaay H.J. and Walsh J.F. (1990). Symposium on onchocerciasis: Conclusions and recommendations. Acta l-eidensia, Vol.59, pp 443-456. Cheke, R.A., M.Dutton, H.S.K.Avissey, M.J.Lehane 1990: Increase with age and fly size ofpteridine concentrationsindifferent membersof theSimuliumdamnosun species complex. Acta Iridensia Vol 59 pp 307 - 314. Cheke, R.A., Howe M.A., Irhane M.J., Millart T., Kone, Baker R.H.A. (1990) The ages of Simulium sirbanun re-infesting the WHO Onchocerciasis Control Programme in Mali: estimates by analysis of pteridine concentrations. Phil. Trans. Roy. Soc. B. Dadzie, KY., Remme J., Alley E.S. and De Sole G. (1990): Changes in ocular onchoc- erciasis four and nrelve months after community-based treatment with ivermectin in an holo-endemic onchocerciasis focus. Trans.roy.Soc.trop.Med.Hyg, 84,pp 103-108. Dadzie K.Y., Remme J., Baker R.H.A, Rolland A and Thylefors B. (1990). ocular onchocerciasis and intensity of infection in the community. III. West African rainforest foci of Simulium sanctipauli. Tropical Medicine and Parasitology, Vol.41, 376-387. Dadzie KY., Remme J. and De Sole G. (1991). Changes in ocular onchocerciasis after two rounds of community-based ivermectin treatment in an holo-endemic i, -t .',:d 33 onchocerciasis focus. Transactions of the Royal Society for Tropical Medicine and Hygiene (in press) Dadzie KY, Remme J., and De Sole G. (1990). The epidemiological impact of vector control in the Onchocerciasis Control Programme in West Africa. II. Ocular onchocerciasis. Acta Leidensia, Vol.59, pp 127-140. De Sole G., Remme J., Dadzie K.Y. (1990). The epidemiological impact of vector control in the Onchocerciasis Control Programme in West-Africa. I. Changes in incidence, intensity and prevalence of infection. Acta lridensia, Vol.59, pp 119-126. De Sole G., Dadzie KY., Giese J. and Remme J. (1990). Adverse reactions following routine large scale ivermectin treatment of onchocerciasis. Iancet, Vol. 335, pp 1106-1107. De Sole G., GieseJ., KeitaF.M. and RemmeJ. (1991). Detailed epidemiotogical mapping of three onchocerciasis foci in the West African savanna. Acta Tropica, Vol.48, pp 203-2t4. De Sole G. and Remme J. (1991). Onchocerciasis infection in children born during L4 years of Simulium control in West Africa. Transactions of the Royal Society for Tropical Medicine and Hygiene (in press). De Sole G. (1990). Migration studies in the onchocerciasis controlled areas of West Africa. Tropical Medicine and Parasitology 41, pp 33 - 36. De Sole G., Baker R., Dadzie K.Y., Giese J., Guillet P., Keita F.M., Remme J. (1991) Onchocerciasis Distribution and Severity in five West African Countries. Bull. Wrld Hlth Org. (in press). Guillet P., Poudiougou P., Back C., Quill6v6r6 D., Seketeli A. (1990). [-a resistance aux insecticides dans le complexe S. darnnosum: Impact operationnel et mesures palliatives. Colloque International sur la lutte contre les insectes vecteurs de mal- adies, Anvers (Belgique) 13 - 14 Decembre 1990. Habbema, J.D.F., Plaisier, A.P., van oortmarssen GJ., Remme J. and Alley E.S. (1990). Prospective evaluation of onchocerciasis control strategies. Acta Lridensia, Vol.59, pp 387-398. Ir Berre, R., Walsh J.F., Philippon B., Poudiougou P., Hendericlor J.E.E., Guillet p., Seketeli a, Quill6v€r€D., Grunewald j., cheke R.A, (1990) The world Health i.t .,.J vOrganizatiog Onchocerciasis Control Programme: Retrospect and prospects Phil.Trans.Royal Soc. [ond. B. 328. pp 72t-729. I-eveque C. (1990). The use of insecticides in the Onchocerciasis Control Programme and aquatic monitoring in West Africa. SCOPE 317 -335. Philippon B., Remme J., Walsh J.F., Guillet P. and Zerbo D.G. (1990) Entomological results of vector control in the Onchocerciasis Control Programme in West Africa. Acta I-eidensia Vol.59, pp79-94. Philippon B., Remme J.H., Quill€v€,rdD. (1990). Lutte contre l'Onchocercose en Afrique de l'Ouest: le Programme Onchocercose, Bilan sommaire de quinze annees. Col- loque "Homme, Sante, Tropiques," Poitiers 14 - l6juin 1990, t2pp. Plaisier, A.P., GJ.van Oortmarssen, J.D.F.Habbema, J.Remme, E.S.Alley. (1990) ONCHOSIM, a simulation model for the transmission and control of onchocer- ciasis. Computer Methods and Programs in Biomedicine,3l, pp 43-56. Plaisier A.P., van oortmarssen G.J., Remme J. and Habbema J.D.F. (1991). The reproductive lifespan of Onchocerca volvulus in West African savanna. Acta Tropicq Vol.48, pp 27 l-284. Plaisier A.P., van Oortmarssen G.J., Remme J., Alley E.S. and Habbema J.D.F. (1991). The risk and dynamics of onchocerciasis recrudescence after cessation of vector control. Bulletin of the World Health Organization, Vol. 69, pp 169-178. Remme J., De Sole G., Dadzie KY., Alley E.S., Baker R.H.A., Habbema J.D.F., Plaisier A.P., van Oortmarssen G.J. and Samba E.M. (1990). Large scale use of ivermectin and its epidemiological consequences. Acta lridensia, Vol.59, pp 177-192. Remme, J., De Sole G. and van Oortmarssen G.J. (1990). The predicted and observed decline in the prevalence and intensity of onchocerciasis infection during 14 years of successful vector control with reference to the reproductive lifespan of O nchocerca volvulus. Bull.Wd.Hlth.Org. Vol.68, pp 33 l-339. Sambq E.M. (1990). OCP Intercountry collaboration. Acta lridensiq 59 pp 383 - 386. Samba, E.M. (1990). Onchocerciasis control in regard to PHC/BHS. Acta kidensiq 59 pp 115 - tl7. t3 * Walsh, J.F. (1990). Review of vector control prior to the OCP. Acta Iridensia,5g pp 61 -78. 35 Yameogo L.,TapsobaJ.M., CalamariD. (1991). l-aboratoryToxicityof Potential Blackfly I-arvicides on some African Fish Species in the Onchocerciasis Control Programme Area. (in press) Yameogo L., Calamari D., Grunewald J., Fairhurst C.P. (1991). The aquatic monitoring and bioassay component of the WHO Onchocerciasis Control Programme in West Africa. Verh. Internat. Verein. Limnol. (in press). d ',4 a a oO. :1 , a: =t- I i \ -\2 5 o L)a o a l: n o t .)(. J ?.*f tE f, a { I a a I \ U ) a oI {Q o- r.- ( o EEo -9 EEE' oE .:o oo ;a b; -tr: o9 E L* oo E: o!= oEuo ! =o r oi: o od; oe E: - d ^-: oc *c ! o ;= 9a ;'9 di sa trc t3(itl t ./t P //) c ii dll a \1 \l)t ilil I I .-+\ ^-i.-lJ?;r o oI z tr, a trJ lrJF aEF @ tu Gg z tr t!o l =x E o o)I z o UJF td EF a tr tiJ utr o, o \ o ! a a6 z o =o zo o & c oO !- o =z :J G -z o -) 6 T =E(5 o -a d z 6 ! G I ; fT t ot o eFz a q o = O C\J o- o ; ,i ,A\r/*lill,\'aTi '\>/>ry', I ., -) I a;e roO, iF-oco -L'a9 6uE o o-I "-UE 063 qt L.-j oe a No E \=C '-..-.v.-.-.-. -.-./. N \ \ I (l, c o N o o o(l- tf) CL o = c o (l, .9 E 'o El-(u L f'-'rJ tJ E. o : o UJ F o () /'o(, oF z I (, I \ \ I ') I 1 I .t' o =o .x(,g .o o E oo ( z z UJ (D ri I I I I I I oo o l- J ( \Y oD .E , f o(D \ ( o -o o .=E = I.-', J \ o @ l! z Y E, f m t 'l ) .ci. -r'/ .\ .i s' I .J