Onchocerciasis Control in the Volta River Basin Area : information paper

WORLD HEALTH ORGANIZATION ORGANISATION MONDIALE DE LA SANTE OCP|74.1 Rev.t June 1975 ONCHOCERCIASIS COMROL IN TTIE VOLTA RIVER BASIN AREA INFORMATION PAPER Background Onchocerciasis, or rlver blindness, is a parasitic disease caused by the threadlike wora oncocerca volvulus whlch affects aE least 2O oillion people in tropical Africa, the Yeoen and @dSouthAoerica.t,1anistheon1yhostofPracEica1signif1canceand onchocerciasis is Eransmitted by the bites of feoale blackflies (Sinuliidae). Among Ehe ioportant clinical manlfestations of onchocerciasis are lntensely itchlng rashes, wrinkllng, thickening and depigoentation of the skin, Ehe characteristlc skin nodules in which the adult rro11as are to Ue touna, and as the Eost serious consequences of the disease, eye lesions leading to blindness. ftre medically nost importanE and largest endemic areas are locaEed in troplcal Africa where the main ,""to. is Sinulir-u dannosd. This blackfly breeds in fast-flowing sEreaos and r1vers.Asaconsequenc@fferingoccurs{roongpeop1ewho1ivec1osetothe river valleys. Ihe area affected In July 1968 a technical conference held in Tunis under Lhe Joint auspiees of usAID, OCCGE and WHO concluded that onchocerciasis control in the west Afrlcan aavanna zone was feasible and that the ElEe had c@etounderEakelarge.scaleacEionagainsEthevecEor Sioulium dannosuo in order to reduce Ehe preva Lence and lntenslty of Ehe disease and to oPen up hitherto deser ted fertile land to hr-oan set tlemenE, livesEock raising and crop grorlng' The savanna area of the Volta Ri.ver basin, in l{est Africa, is one of the lrorst endemic onchocerciasis zones of the world. rn this area of approximately 7oo ooo kn2, wtrlch includes parts of Dahmey, Ghana, Ivory Coast, Mali., Niger, Togo and Upper VoLta, it ls estinated Ehat over a nillion people aie inflcted and Chat, as a consequence, at least 50 0OO of these are blind wtrtle Eany oore have serlous impaitment of sighc' Ttre association of proxioity to the rlvers and the risk of onchocerciasis wae recognized by rhe local populations, who moved froo the fertile valleys Eo settle ln relatively infertile lands. The disease Ehus constttutes for the area the most imporEanE slngle deterrent to hrman settlement, and the subsequent economic developoent of the fertlle valleys wtrich lie uninhabited and unproductive. Furtheruore, the PersiscenE and critical effects of drought in the eahel and tire savanna, foLlowing the fatluie of the rains for slx successlve years, have gravely conpllcated the already precarious soclo-econooic balance in the Volta River basin area' EvenEs leading to the Programe I I ; The recomendaElons of the Tunis meeting were taken intg consideration by alL the parties concerned. rn 1969 and 1970 the seven Goveinments involvedl confirued thelr ioteresE in such a regional onchocerciasls control progra*e and formulaEed requests in this sense to UNDP' I,IHO then drew up a proposal designed io assign. to Ehe Volca Rlver basin a PreParaEory Assistance to coverilents Missioi (pAC Uisslon), for wtrich the Adoinistrator of LIMP agreed to provlde Ehe necessary funds. I|IIO was designated as Executing Agency, in assoclation lrith FAo. In JuIy LglO ac a trleer,ing in Geneva (orfanized joincly by UNDP and WIIO, on the proposal of IBRD) "g..h"r,t was reached on the oandate of ttre Mission between Lrl{DP' FAo, l{tlo, IBRD, OCCGE and the Government of Ghana,rrConseil de lrEntenterr, EED and USAID' 1 D"hor.y, Ghana, Ivory Coast, Mali, Niger, Togo and Upper Volca' I OCP|74.1 Rev.1 page 2 The PAG Mission had a major twofold objective. In the health sector, i.E was requestedto PrePare a plan of work Eo achieve cont.rol of onchocerciasis over the enEire recmended Progrrrnrne area, taking into accounc economic developnenE of reclaimed zones; to work out the expected cogcs and benefits of the scheme; and to analyse the possible financial resources available. In the econooi.c sector, ic was called upon to identify zones within the progrennne area which owing Eo their economic potential and location in relation to centres of populationdenslty, offered developmenE possibilities; lt was requested also to draft preliminary Eerms of reference for feasibility studies to be conducEed later in these areas. The Government of Upper Volta accepted to acE as host to the PAG Mission whose head-quarters ltere set up in August L97L at Ouagodougou in premises placed aE the disposal of theMission by the Government. Operating fron Ouagadougou, the Mission benefited from the full collaboration and encouragement of Ehe GoverrmenE of Upper Volta as well as of the other six countrles in which tt has carried out its actlvities. Thus Ehe PAG Mission carried ouc iEs work from nid-1971 through L972 aad. was extended ro cover 1973 agaln under LIMP regional funds with $flIO as Executlng Agency and FAO as AssociateAgency. Early it L972 Ehe ExecuEive heads of UMP, FAO, IBRD and WIIO decided ro establish a Steering Conrmittee for onchocerciasis Control corprising a representative from each of thefour agencles to coordinaEe action. Ihe Steering ComitEee has accordingly meE regularly to monitor progress and resolve problems. The reporE The Report of the PAG Mission, suppleuented by a series of technical annexes, was submicted on 2O August 1973 to the GovernmenEs of the seven counEries of the Volta River basin area. This report lncludes a detailed analysis of onchocerciasis and its socio-econonic inplicationsin the area aa well as a costed proposal for launching an onchocerciasis control progreme in L974, and suggestions for the economic developnent of the fertile valleys and oEher abandoned areas of the Volta River basin. No less than five years of concerEed study and effort were needed Eo determine uith the necessary precision the conditions under which an onchocerciasis control progreme could be launched with the best chances of success. Onchocerci.asis can be conLroLled through a campaign againsE the parasite, the vector, or both. Presently two drugs are available for the cheoo- EheraPy treatment of onchocerciasls: suremln and dlethylcarbemazine. However, although these drugs can be used with little difficulty and risk, under close medical supervision, forindividual treatment of patients sufferi.ng from onchocerciasis, their u6e in mass chemoEherapy compaigns rai.ses problems that require further study. In Ehe absence of an acceptable drugfor oass chemotheraPy, control of the insect vector offers the only oeans at present for inEerruptlng transmission of the disease. The mechanical elinination of S. damnos'm breeding sices (e.g. through the consErucEion of dams and the regularizat.ion of rffiUEdTis not economically feasible, although in restricted areas it could be a consequence of certain river managenenE projecEs. Thepossibility of controlling this vector with biological agents is being investigated under a research Progreme Jointly supported by che GoverrmenE of Canada and OCCGE, buE the developent of an effective biological control methodology will require rnany years. InsecEicides consticute aE presenc the only effecEive means of interrupEing onchocerciasis transmission. As the fLight range of the adult S. daonosuo may, i.n favourable circumstances, exEend Eo as much as 15O km, an aEtack on the adult fly would require the insecticide EreatmenE of an irunense area and is not considered feasible. As Ehe vecEor breeding siEes are resEricEed to fasE flowing stretches of rivers, control of S dannosum ln the Volta River basin area is beidirected againsE Ehe larvae and is based on weekly applicaEion of insecEicide imediately upsEream from the larval breeding places. a a I l n8 OCPl74.1 Rev. I page 3 Because of uhe inaccessibiliEy by land of nany of the breeding sites of Simullum, Ehe only feasible nethod of applying the lnsecticide is frm the air. In the case of large rivers that are sufficienEly straight, llght planes can be used, but narrow tqristing waterways and those overhung by forest require the use of helicopEers. Ihe selection of an insecticide was based on specific criteria: the candidate compound was required Eo have low toxicity for man and vertebrate in general and, whlle being very effecElve agalnst blackfly, have as little effecC as posslbl€ on noo-target fauna. Only biodegradable cornpounds with little residual acEivity were considered to make sure thaE no contamination of the environtrent could take place. Ttre ineecticides seLected were studied by hydrobiologlsta and fishery biologists in West Afrlcan laboratoriea and in field condiEions to confiro their suitabtllty. Additional investigaEions are presently under way wtriLe long- term hydrobiological studies of typlcal treated stretches of the qratercourses are being carried ouE to ensure that the blological equilibrir.rn of the rlvers is not seriously disturbed by the control operatlons. The effects of the insecEicide on the distribution and abundance of S. daonosr-ro are subJect to continuous oonlEoring Co ensure that only breeding siEes known Eo harbour vector larvae are treaEed. The monitoring of these iDportant asPects is shared with an Ecological Panel attached to the Programe which advises on measures to ensure the satis- factory proEection of the environment. Because of the long life of the adult woru i.n the hrman host, sufferers frm onchocerciasis may remain lnfective for as long as 15 years even if not re-infected. the duraclon of a campaign to prevent the disease by elininating its lasect, vector Eust therefore be not less than this length of tlme after the last nerr case in the programe area. This is why che Prograurne is scheduled to lasL 20 years. Ihe effects of the vector control caopaign on the prevalence and severity of onchocerci.asis are continuously being monltored by epidemiologlcal evaluation t€enso It is hoped that cheooEherapy proEocols will soon be developed for the effective and safe treahent of those patients so severely infecced that Ehey could become progressi.vely blind in the next few years in spite of tnterruption of the disease transmission. Applled research is another inportant c@ponent of the Onchocerciasis Control Progra-e. Special investigatlone being carri.ed out on both the entomological and medical aspects of onchocercla, S. daonosr.m sls include cytotaxonomic studles of the Slnulirm diurrrosLur populations, teats with new insecticide"fiF6ffiEil? complex, saopllng of , susceptibility and/or I ! resistance of Simulir.rm larvae to lnsecEicldes, study of the correlation between uigration of adult Sinulii iiFilffiorological phenomena, effects of insecticides on non-target aquaEic organisos, the dynaolcs of onchocerciasis tran$triseion and studiea on new methods of treatment. Personnel trainlng also forms a significant eteoent of the Programe to ensure its progressive stafflng by specialists of the seven countries concerned. Attention is being paid to the need Eo train nationals of the Progrnrnme area abLe graduaLly co take over Ehe responsibillty for surveys and different aspects of the Progra'nme and subsequently to run the Programe itself. The repopulation and/or settlemenE of the uninhabited fertile area6 freed from che disease is a major objective of the Onchocerclasls Control Prograr-e. Such action would also peroit developo.ent meaaures to be taken in areas of high populatlon density. IE is expected that major reclamation of deserted lands w111 be posslble sme 18 monEhs after the scart of lnsecticide treatment in the zone concerned. In many cases the lands to be repopuLated or colonized will require infrastructure in tetms of road networks, water supply and medical, educatlonal and agricultural extension services. In other instances lmprovement of such faclllties will be essential for the success of repopuLaEion and settlement. The required 1ow and oedLrm leve1 agricultural extension services will, in some lnsEances, need backstopping by profeesional officers in the relevant disclplines. OCPl74.1 Rev.l page 4 The main responsibility for the econmic developnenc projects remains wtEh each of theGovernments which may however request external aesistance in the neEhodology and planning ofactivities, and external funds for their financing. A series of reclamation plans based onthe develofent of agriculture and stock raising have been studied and costed, as examples,to assist national authorities. Launching of the Programe The Programe is necessarily a joint undertaking and requires the futL collaboration of each of the seven countries concerned. The prograuue is governed by an Operational Agreeoent signed at Accra on l November 1973, wtrich brings into associat,ion the GoverroenEs and WltO, cheExeeuting Agency. The Operational Agreement is suppleoented by separate country protocol6 wtrich esEablish the contributions of the Particlpating Governments.' It was decided to implerent the Progreme by staggering Ehe ineepEion of operations over a period of three years, from 1974 co 1976, as it would be unrealistic Eo atteEpt Eo launch the vector controL oPerations simultaneously over such a large area. Ihe first phase thus starEed at the beginning of the dry season in Decenber L974, when rhe S. dannosqm population was on the decrease, and concentrated iniEiall y on a zone of heavy infestat,ion ln the BlackVolta, Cmo6-L6raba, Bandama, Nzi and Banifing basins as a logical exEension of the old FED/OCCGE campaign. Ttre work was extended in a second phase to the Red Volta, t{hi.te Volta and Daka basins in 1975. Phase three of operations, from 1976 onwards, will cover the basins of the Oti-Pendjari, and of the Mali, Ivory Coast, Upper Volta, Niger and Dahomey crlbutaries of the Nlger Rlver. The experience gaEhered ln the first six months of operatlons has indicated that the methods adopted by the Programe are very effective. The insecEicide treatmenE of the rivers by helicopter and fixed-wlng aircraft in the dry season 1ed to the achievement of significant control in the Phase I area. A large scaLe intercountry Prograrme of this naEure requires Ehe coordinaEion of efforts at Ehe national level and the consiscenE support of each participating Government. To this end each of the seven Governoencs concerned has set up a National Onchocerciasis Comittee to assuoe responsibiliEy for coordinating the technical, social, budgetary and loglsEic support of the Progranme at the nationaL level. Such national comittees play a key roLe ln ensuring Ehe provision of Government councerpart contributions, the 1lnk between the Onchocerciasis Control Progr*'rme itself, the repopulation and settlemenE activi.ties and projects for the subsequenE econooic developent of the freed zonea, and other necessary rneaaures. It is estimaEed thac the overall Programe will require funds in Ehe reglon of some $ 12O nillion over a ElrenEy-year period, from L974-L994. In the first lnstance, deEailed planning covers the six years L974-I979. IBRD had accepted to oobilize conEributions to the Programe and to act as che cusEodian of the Special Fund for Onchocerciasi.s ConErol for Ehe financing of activities. The Fund Agreement was signed on 7 May 1975 in Washington, D.C. As ExecuEing Agency, WHO assuoes the Eechnical responsibility, in conjunction with the Governments involved, for the technical and logistic managemenE of Ehe Programe. WIIO has aPPoinEed a Progremne Director wtro is assi.sEed by four specialized sections Sin-ul:Llao Control, Epideniology and Public ltrealth, Economic Development supporE and AdminisErative support). The Programe headquarters is locaEed at Ouagadougou, Upper Volta, in view of its central position in the affected area and ln one of the most aorely afflicted of the seven counEries involved. LJNDP and FAO will be associated with the Programe Eo assi.sE Governments, aE Eheir requesE, in planning aod implementing national projects and schemes in Ehe economic field where external assistance is required co develop the zones freed of onchocerclasis. Ihe Steering Coruuittee remains as the execuEive organ of the Prograrune with the duty of studying and recomending che plans of work prepared by Ehe Executlng Agency. A JoinE Coordinating Comnittee has been set up grouping t.ogeEher the seven parCicipacing countries, the donor nations and insEitutions, and the four sponsoring agencies. The ComiEtee, headed by an Independent Chairman meets once every year to review the annual budget and exercise general supervision over Ehe Prog*rame.." I I !