Onchocerciasis control in the Volta river basin area: information paper

WORLD HEALTH ORGANIZATION ORGANISATION MONDIALE DE LA SANTE May 1980 ONCHOCERCIASIS CONTROL IN THE VOLTA RIVER BASIN AREA INI'ORMATION PAPER Backgrou4d Onchocerciaeis, or rlver blindness, ls a parasitic disease caused by the threadlike worm onchocerca volvulus which affecte from 2O to 40 miIllon people in Eroplcal Africa, the Yemen and parts of Central and South Amerlca. Man is Ehe only host of practical slgnlficance and onchocerciasls ls transmttted by the bites of female blackflies (Simuliidae). Aoong the important clinical manifestations of onchocerciasis are intense itching, rashes, wrinkling, thickening and depigmenEaEion of the skin, the characteristic skin nodules in which the adult worms are to be found, and as the most seri.ous consequences of the disease, eye lesions leading to blindness. The medically most important and largest endemic areas are located in tropical Africa where the main vector is Slmulium damnosum. This blackfly breeds in fast-flowing st,reams and rivers. As a consequence, the greatest suffering occurs among people who live close to Ehe river va11eys. Ihe savanna area of the Volta River basin, in West Africa, is one of the worst endemic onchocerclasls zones of the world. In this area, which includes parts of Benin, Ghana, Ivory Coast,, Mali, Nigerl Togo and Upper Volta, iE is est,imated that over a million people are infecEed and that, as a consequence, at least lOO OOO of these are blind while many more have seri.ous impairment of sight. The association of proximity to the rivers and Ehe risk of onchocerciasis was recognized by the local populations, who moved from the fertile valleys to settle in relatively infertile lands. The disease thus consEiEutes for Ehe area the most important single deterrent to human settlement, and Ehe subsequent economic development of the fertile valleys which 1ie uninhabited and unproductive. Furthermore, the persistent and critical effecEs of drought in the sahel and the savanna, following the failure of the raj.ns for six successive years, have gravely complicated the already precarious socioeconomic balance in Ehe Volt,a River basin atea. Events leadins to the progralEne In July 1968 a technical conference held in Tunis under the joint auspi.ces of USAID,I OCCGE2 and WHO3 concluded that onchocerciasis control in the West African savanna zone $/as feasible and that the time had come to undertake large-scale acEion against the vecEor Sirmrlium damnosum in order to reduce the prevalence and int,ensity of Ehe disease and t,o open up hitherto deserted fertile land to human settlement, livestock raising and crop growing. ' ,nra.d SEates Agency for International Development.2 Org^ni."rtion for Coordination and CooperaEion in the Control of the Major Endemic Diseases. 3 I.Iorld Health organization. wPf74.1 Rev.4 I i I I The area affected ocPf74.1 Rev.4 page 2 The reconrnendations of the Tunis meeting were taken into consideration by alt the parties concerned. In 1969 and 1970 the seven Governments involvedl confirmed their interest i.n such a regional onchocerciasis control progranrne and formulated requests in this sense to UMp.2 WHO then drew up a proposal designed Eo assign to the Volta River basin a PreparaEory Assistance to Governments Mission (PAG l"lission), for which the AdminisErator of LJMp agreed to provide the necessary funds. WHO was designated as Executing Agency, in association with FAO.3 In July L97O at a meeting in C,eneva (organized jointly by UNDp and WHO, on the proposal of the World Bank) agreement. was reached on the mandate of the Mission between UNDP, FAo, wHO' the World Bank, OCCGE and the Government of Ghanar t'Conseil de 1'Ententett, EDF4 and USAID. The PAG Mission had a major twofold objective. In the health sector, it was requested to PrePare a plan of work to achieve cont,rol of onchocerciasis over the entire reconmrended Programne area, taking into account economic development of reclaimed zones; to work out the expected costs and benefiEs of the scheme; and to analyse the possible financial resources available. In the economic secLor, it was calIed upon to identify zones within the progranrme area which owing to their economic potential and locaEion in relati.on to centres of population density, offered developmenE possibilities; it was requested also to draft preliminary terms of reference for feasibility studies to be conducted later in these areas. The Government of Upper Volta accepted to act as host to the pAG Mission whose head-quarters were seE up in August L97l at O,ragadougou in premises placed at the disposal of theMission by the Government. operating from ouagadougou, the Mission benefited from the fu11 collaboration and encouragement of the Government of Upper Volta as well as of Ehe other sixcountries in which it. carried out its activities. Thus the PAG Mission carried out it,s work from mid-1971 through L9l2 and. hras ex.ended tocover 1973 again under UNDP regional funds with wHo as Executing Agency and FAo as AssociateAgency' Earty in 1972 the Executive heads of ump, FAo, Ehe world Bank and wHo decided toestabrish a Steering conrmittee for onchocerciasis control comprising a representative fromeach of the four agencies to coordinate action. The steering cormittee has accordingly megregularly to moniEor progress and resolve problems. The report The ReporE of the PAG Mission, supplemented by a series of technicar annexes, wassubmitted on 2o August 1973 to the Governments of the seven counEri.es of the Volta River basinarea' This report included a detailed analysis of onchocerciasis and its socioeconomicimplications in the area as well as a costed proposar for raunching an onchocerciasis controlPrograme in 1974, and suggestions for the ""o.ro.i" development of the fertile valleys andother abandoned areas of the Volta River basin. No less than five years of concerted study and effort were needed to determine with thenecessary precision the conditions under which an onchocerciasis control programne courd belaunched r^/ith the best chances of success. onchocerciasis could be controrred through acampaign against the parasite, the vector, or both. Two drugs were available for the chemo_therapy of onchocerciasis: suramin and diethylcarbamazine. However, although these drugscould be used r^'ith 1ittle difficulty and risk if individual treaEment of patients sufferingfrom onchocerciasis was given under close medical supervision, their use in mess chemotherapycampaigns raised problems that required further st,,ray. rn Ehe absence of an acceptable drug i::"]:i:.;:;-::ril:r];"llljl", or rhe insecr vector trrered rhe only means ror intlrrupring 1 2 3 4 Benin, Ghana, Ivory Coast, Mali, Niger, Togo and Upper Vo1ta. United Nations Development programne. Food and Agriculture organization of the United Nations. European Development Fund. I ) I oceft+.1 Rev. 4 page 3 The mechanical elimination of S damnosum breeding sites (e.g. through the construcEion of dams and Ehe regularization of river beds) was not economically feasible, although in restricted areas it corrld be a consequence of certain river management project.s. Thepossibility of controlling this vector with biological agents was invesEigated under a research PrograllEne joinEly supported by the Government of canada and oCCGE, but the development of an effective biological control methodolory would have Eaken many years. Insecticides weretherefore at that time the only effective means of interrupting onchocerciasis transmission. As the flight range of the adult S. damnosum may, in favourable circumstances, exceed 3OO km, an attack on the adult fly would f,a.r. req"ired Ehe insecticide treatment of an itrmensearea and was not considered feasible. As the vector breeding sites are restricEed to fasE-flowing sectors of rivers, control of S. damnosum in the Volta River basin area is beingdirected against the larvae and is u..ti-Ely application of insecticide irrnediately upstream from Ehe larva1 breeding places. Because of the inaccessj.bllity by land of many of Ehe breeding siEes of Simulium, theonly feasible method of applying the insecticide r^7as from the air. rn the "iilE"rg"rivers that. are sufficiently straight, light planes can be used, but narrow twisting water- ways and those overhung by foresL requi.re the use of hericopters. The selection of an insecticide was based on specific criteria: the candidate compound was required to have low toxicity for man and vert,ebrates in general and, while being vLryeffective against blackfly, to have as little effect as possible on non-target fauna. onlybiodegradable compounds with little residual activity were consi.dered to make sure EhaE nocontamination of the environmenE could take place. The insecticides selected were studiedby hydrobiologist.s and a fishery biologist in West African laboratories and in field conditionsto confirm their suitability. Because of the long life of the adult worm in the human host, sufferers from onchocerciasis may remain infective for as long as 15 years even if not reinfected. Therefore the durationof a campaign to Prevent the disease by eliminating iEs insecE vector must not be less thanthis lengEh of time after the last new case in the progranune area. For this reason theProgranrne was scheduled to last 20 years. The effecEs of the vector control campaign on the prevalence and severity of onchocerciasis must be continuously monitored by epidemlological evaruation Eeams. The onchocerciasis control Progranune is supported by appropriately appried researchprojects, particularly in the fields of chemotherapy, vector conErol and protection of theenvironment' Another imPorEant elemenE of the prlgraurne is personnel training, to ensure theprogressive take over of the Progranrme by specialists of the seven countries concerned. rhe repopulation and,for seEtlement of the uninhabited fertile areas freed from the diseaseis a major objective of the onchocerciasis conEror prograuure. such action should also permiEdevelopment measures to be taken in areas of high popuration densiEy. rn many cases the lands t,o be repopulated or colonized required infrastructure in termsof road networks, water supply and medical, educational cnd agricultural extension services.rn oEher instances improvement of such facilitles was essential for the success of repopulationand settlement. The required low and medium leve1 agricultural extension services in someinsEances, needed backst,opping by professional officers in the relevant disciplines. The main responsibility for the economic development projecEs remained with each of theGovernmenEs which could however request external assistance in the methodolory and planning ofactivities, and external funds for their financing. A series of reclamation plans based onthe development of crop and livestock farming r.." studied and costed., as exampres, to assistnational authorities. ocPf74.1 Rev.4 page 4 Launching of the progrqllle The prograrmne i-s a joint undertaking by the seven countries concerned. An Operational Agreement signed in Accra on 1 November 1973 brought into association the Governments and lfHO, Ehe Executing Agency. The Operational Agreement 'v,ras supplemented by separate country protocols which established the specific contribution of each government. The C,overnments set uP national onchocerciasis cormnittees, which were responsible for ensuring provision of the counterPart contributions by the Governments and for liaison at the national Ievel between the progranrne, the repopulation and settlement act,ivities, and the economic developmentprojects in the areas concerned. These conrmittees have met annually since 1977. As Executing Agency, WHO is responsible for the technical and logistic management of theprograrEne. It set up Ehe PrograrEne headquarters at Ouagadougou in Upper Volta, appointed adirector, and set up four specialistunits, (vector control, Epidemiolory and public HeaIEh,Economic Development' Support and Administrative Support), wit,h the necessary personnel and infrastructure. It also set up a Scient.ific Advisory Panel to keep an eye on the technical aspects of the prograflme. The World Bank agreed to mobilize contributions for implementation of the progran,rne and to act as custodian of the Special Fund for Onchocerciasis Control for the financing of activities. The Fund Agreementwassigned in Washington on 7 May 1975. A detailed plan of oPerations provided for an overall cost of about $ 60 million for an initial six-year period from 1974 to L979. The St.eering Conrnittee remained the executive organ of the programne, wiEh the t.ask of studying the plans of work prepared by the Executing Agency and making reconmendations on them. The Conrmit.tee set uP an Ecological Panel to attend to environmental protection, together with an Economic Development Advisory Panel. A Joint Coordinating Comnittee representing the seven participating countries, the donor countries and instituEions, and the four sponsoring agencies, and headed by an Independent Chairman, r^ras set up in June 1974. This Cournittee has met each year to consider the annual budget and exercise general supervision over the planning and implementation of the prograurne. The vector control operations concentrated initially on an intensely infested zone consisting of the basins of the Black Volta, the Qomo6-L6raba, the Bandama, the Nzi and the Banifing, a logical extension of the campaign already carri-ed out jointly by EDF and OCCGE. In 1976 the activities were extended to the basins of the Red Volta, the white Volta and the Daka. From 1977 onwards the operations covered the oti-pendjari basin and the right hand tributaries of the Rlver Niger in Mali, Ivory Coast, Upper Volta, Niger and Benin. In 1978 oPerations were also undertaken in the Sassandra and }.,larahou6 basins, and later in the Como6basin to the south of the initial boundary of the Progranrne. The progranrne no!, covers an area of 765 OOO kn2. Entomological surveillance is carried out by aerial reconnaissance through a network of six sectors and 21 sub-sectors distributed Ehroughout the progrartrne area and linked to each other and to programne headquarters by radio t.ransceivers. The blackfly collection points in these sectors number about 3OO. The catches are counted and exami.ned to determine the morpholory, physiological age and infestaEion rate of the blackf ly. Ihe entomological situation is kept under continuous evaluation. IE is on the basis of this evaluation that the weekly insecEicide treatments of water- courses are planned. The frequency of treatments is based on the biological cycle of the vector larvae. The insecticide used since the start of operations is a biodegradable organo- phosphorus compound, a 20% emulsifiable concentrate of Abate. The dosages are calculated according to the rate of flow of the watercourses in the various hydrological basins, for underdosage rnay be just as harmful to Ehe efficiency of the programne as overdosage is harmful to non-target fauna. The insecticide is applied from the air. 1 I ocPf 74.1 Rev.4 page 5 The aerial operations are conducted under contract by a conrnercial company. They involve the use of eight helicopters and two fixed-wing aircraft, operating from tr^zo bases: one at Bobo-Dioulasso in Upper Volta which serves the western zone, the other at Tama16 in Ghana which serves the eastern zone. In the rainy season some L8 O0O km of rivers are kept under continuous surveillance and are treateC wherever necessary. By the end of L979 over 28 OOOflying hours had been devoted to this work and it was believed that transmission had been interruPted in about 75% of the total geographical area covered by the prograrrne. Since 1975 the Epidemiological Evaluation Unit has been making a basic evaluarion of thedisease. It has performed parasitological and ophthalmologicaL examinaEions of theinhabitants of a certain number of villages selected in advance, which made up the basic sample,in order E.o determine the Prevalence of onchocerciasis and Ehe endemicity and blindness raE,es.This evaluation is made at two levels. 0n the one hand E,here is simple evaluation, which aims to determine Ehe prevalence of Ehe disease and visual acuity by age and sex. 0n theother hand Ehere is detailed evaluation, rnhich uses more Ehorough examinaEions to assess theprevalence of ocular onchocerci.asis, the proportion of irreversible lesions and the blindnessrates. The sample is made up of 419 villages in which a Eotal of lo5 355 persons have beenexamined. In actual fact the medical teams had performed 115 41r examinations by the end of1979, as the inhabiEants of some villages had been examined several times. Since l97g asecond evaluation has been undertaken in the villages where the basic evaluation started in1975' Three years of vector control are regarded as Ehe minimum period for detect.ing anytrend in the disease. The first stage of this second evaluation, which covered 25 of chevillages re-examined where transmission had been interrupted for three years, showed that nochild under five years had contracEed the disease and that in children aged 5-9 years theprevalence had dropped by as much as 507.. Besides these very tangible results, a reduction inparasite counEs in infecEed subjects and a stabilization of the eye lesions should also beobserved in due course. The Economic Development unit undertook to corlecE alI availabre data on the developmentProjects in progress or in preparation, at the national level and regional level, in Ehe sevenParticiPating st'ates. up to 1979, Ehe year when Ehis task was taken over by the Governmenrs,the unit reported each year to the Joint coordinating committee. The unit assisEs missionsinvolved in such development by making the necessary conEacEs and providing whaE basic daEait has available. since January 1980 lE has been toordinating a training and researchprogranme in health economlcs. At Ehe same time the prograrmne is carrylng out and financing acEiviEies for surveillanceof the aquatic medium and research on entomolory, vector ecolory, vector control and generalepidemiolory, together with medical, parasitological and chemotherapeutic research. Duringthe first six-year phase, over $ 3.5 million weie spent on these activities. During the same period, with the assistance of specialist instituEes, the prograntrnedeveloped Eheoretical and practical training courses in the enEomolory, cytotaxonomy,parasitolory and ophthalmolory of onchocerciasis. During Ehe first pt,u." about 75 nationalsof the ParticiPating states of the progranme and of other African councries took these courses.Moreover,2l fellowships for studies in entomolory, hydrobiology, pestici.de science,parasitolory, epidemiolory, pubric'health and ophthalmolory were awarded to nationals of theseven countries of the prograinne. The progrartrne rnas visited by about 40 wHo specialistsworking in Africa, who came singly or in groups to obtain informaEion on the spot about itsmethods and techniques in order to redirecE their or,rn activities. The total cost of Programne acEiviEies during the first phase from 1974 to L979 wasapproximately $ 54 million. ocPf74.1 Rev.4 page 6 Second phase 1980- 1985 The structures initially set up have been simplified. In accordance r^rith a new Memorandum of Agreement, approved by the seven Participating Countries at the meeting of National Onchocerciasis Conrnittees in Bamako tn L979; aI1 the scientific, technical and economic ad.zisory panels and committees now form only a single Expert Advisory Comnittee (EAC), with an Ecological Sub-group; the Joint Coordinating CorEnittee remains and is now ca1led the Joint Progranrne Conmittee (JPC), with a chairman elected annually at each session; the National Onchocerciasis Cormnittees have also been kept; the Steering Comnittee remai-ns under a new name, the Conmrittee of Sponsoring Agencies. Since September 1979 a new Onchocerciasis Fund Agreement for the period I98O-1985 has been signed in l^lashington by the Governments of Belgium, the Federal Republic of Germany, France, JaPan, Kuwait, the Netherlands, Switzerland and Ehe United States of America, and by the International Bank for Reconstruction and DevelopmenE and the International DevelopmenEAssociation, the United Nations Development Programne and the WorId Health Organization. Canada, Norway, Saudi Arabia and the United Kingdom, together with the African Development Bank and the OPEC Special Fund, have also undertaken t.o contribute to the onchocerciasis Fundduring the second phase. At the end of 1979 the eslimated budget for the second phase was $ 106.7 million. The participating governments are to contribute 1% of the cost Studies are in Progress concerning possible extensions of the vector.control activities t.o the south of the Present limits of the programe in Benin, Ghana and Togo. To conduct these studies four new sub-sectors have been set up in the zones concerned. A document surunarizing these studies is to be submitted to the Joint Progranrne Cormnit.tee in December I9gl. As regards the long-term prospects of the prograrEne, the DirecEor-General of WHO set up an independent conrnission in 1978 to consider what Ehe entomological situation will be in theyears to come and what action and resources will be needed to deal with it. The work of the conrnission will form the basis for a final report to be submitted to the Joint progranme Cormnittee in December 1981. I I a