Onchocerciasis, Or River Blindness, Is a Parasitic Disease Caused by The

WORLD HEALTH ORGANIZATION ocPf74.1 Rev.2

ORGANISATION MONDIALE DE LA SANTE November 1976

I ONCHOCERCIASIS CONTROL IN THE VOLTA RIVER BASIN AREA I INFORMATION PAPER

Backgro und

Onchocerciasis, or river blindness, is a parasitic disease caused by the threadlike worm Onchocerca volvulus which affects at least 20 million people in tropical Africa, the Yemen and parts of Central and South America. Man is the only host of practical significance and onchocerciasis is transmitted by the bites of female blackflies (Simuliidae).

Among the important clinical manifestations of onchocerciasis are intense itching, rashes, wrinkling, thickening and depigmentation of the skin, the characteristic skin nodules in which the adult vJorms are to be found, and as the most serious 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 Simulium damnosum. This blackfly breeds in fast-flowing streams and rivers. As a consequence, the greatest suffering occurs among people who live close to the river val1eys.

The area affected

The savanna area of the Volta River basin, in West Africa, is one of the worst endemic onchocerciasis zones of the world. In this area of approximately 7OO OOO km2, which includes parts of Datromey, Ghana, Ivory Coast, Mali, Niger, Togo and Upper Volta, it is estimated that over a milIion people are infected and that, as a consequence, at least 50 OOO of these are blind wlriIe many more have serious impairment of sight.

The association of proximity to the rivers and the risk of onchocerciasis was recognized by the local populaEions, who moved from the fertile valleys to settle in relatively infertile lands. The disease thus constitutes for the area the mosE important single deEerrent to human setElement, and the subsequent economic development of the fertile valleys which 1ie uninhabited and unproductive. Furthermore, the persistent and critical effects of drought in the sahel and the savanna, following the failure of the rains for six successive years, have gravely complicated the already precarious socioeconomic balance in the Volta River basin area.

Events leadins to the programme

In July 1968 a technical conference held in Tunis under the joint auspices of USAID, OCCGE and WHo concluded Ehat onchocerciasis control in the West African savanna zone was feasible and that the time had come to undertake large-scale action against the vector Simulium damnosum in order to reduce the prevalence and intensity of the disease and to open up hitherto deserted fertile 1 and to human setLlement, livesEock raising and crop growing. The recommendations of the Tunis meeting were taken into consideration by all the parties concerned. In 1969 and l97O the seven Governments involvedl confirmed their i-nLerest in such a regional onchocerciasis conErol programme and formulated requests in this sense to UNDp. I^IH0 then drew up a proposal designed to assign to the Volta River basin a preparatory Assistance to GovernmenEs Mission (PAG Mission), for which che Administrator of uNDp agreed to provide the necessary funds. WHO was designated as Executing Agency, in association with I FAO. In July 1970 at a meeting in Geneva (organized jointly by UNDp and WHO, on Ehe proposal I of the World Bank) agreement was reached on the mandate of the Mission between llNDp, FAO, wHo, trConseil t the World Bank, OCCGE and the Government of Ghana, de lrEntenteil, FED and USAID. I 1 Benin, Ghana, Ivory Coast, Ma1i, Niger, Togo and Upper Volta ocPf74.1 Rev.2 page 2

The PAG Mission had a major twofold objective. In the health sector, iL was requested to PrePare a plan of work to achieve control of onchocerciasi-s over the entire recommended pro8ralune area, taking into account economic development of reclaimed zones; to work out the expecEed costs and benefits of the scheme; and to analyse the possible financial resources I available. In Ehe economic sector, it was called upon to identify zones within the progranrne I area which owing to their economic potential and location in relation to centres of populaEion density, offered development possibilities; it was requested also to draft preliminar)r term; of reference for feasibility studies to be conducted later in these areas.

The Government of Upper Volta accepted to act as host to Ehe PAG Mission whose headquarters were set up in August l97L at Ouagadougou in premises placed aL the disposal of the Mission by the Government. Operating from Ouagadougou, the Mission benefired from rhe fu11 collaboraE.ion and encouragement of the Government of Upper Volta as well as of the other six countries in which it carried out 1ts actl-vl-ties.

Thus the PAG Mission carri,:d out iLs work from mi-d-197J thrtrugh L9l2 and was extended to cover 1973 again under UNDP regionaL funds with WHO as Executing Agency and FAO as Associate Agency. Early in L97Z the Executive heads of tlNDP, FAO, the l^lor1d Bank and WHO decided to establish a Steering Cornmittee for Onchocerciasis Control comprising a representative from each of the four agencies to coordinate action. The Steering Commitree has accordingly met regularly to monitor progress and resolve problems.

The report

The Report of the PAG Mission, supplemented by a series of technical annexes, was submitted on 2O August 1973 to the Governments of rhe seven countries of the Volta River basin area. This report includes a detailed analysis of onchocerciasis and iEs socioeconomic implications in the area as well as a costed proposal for launching an onchocerciasis control progrErrrme Ln 1974, and suggestions for the economic development of the fertile val-leys and other abandoned areas of the Volta Ri-ver basin.

No less than five years of concerted study and effort were needed ro determine with the necessary precision the conditions under which an onchocerciasis control progranrne could be launched wiEh the best chances of success. Onchocerciasis can be controlled through a campaign against the parasite, the vecEor, or both. Presently two drugs are available for the chemotherapy Ereatment of onchocerciasis: suranin and diethylcarbam:rzine. However, although these drugs can be used wirh 1ittle difficulty and risk under cLose medical supervision, for individual treatment of paEients suffering from onchocerciasis, their use in mass chemotherapy campaigns raises problems that require further study. In the absence of an acceptable drug for mass chemotherapy, control of the insect vector offers the only means at present for interrupting transmission of the disease.

The mechanical elimination of S. damnosum breeding sites (e.g. through the construction of dams and the regularization of river beds) is not econonicaLly feasibLe, although in restricEed areas it could be a conseqLrence of certain river management projects. The possi- bility of controlling this vector with biological agents is being investigated under a research prograrune jointly supported by the Government of Canada and OCCGE, but the development of an effective biological control methodology will require many yearri. Insecticides consEitute at present the only effective means of interrupting onchocerciasis transmission.

As the flighE range of the adult S. damnosum may, in favourable circumstances, exceed 150 km, an atEack on the adulf fly would require the ins;ecticide treatment of an inrnense area and is not considered feasible. As the vector breeding sites are restricted to fast-flowing sectors of rivers, controi of S. damnosum in the Volta River basin area is being directed against the larvae and is based on wcekly application of irs;,:cticide innnediately upstrenm from the larval breeding places. OCP/74.1 Rev.2 page 3

Because of the inaccessibility by land of many of the breeding sites of $!111!!9., th" only feasible method of applying the insecticide is from the air. In the case of large t rivers that are sufficiently straight, light planes can be used, but narrow twisting water- ways and those overhung by forest require Ehe use of helicopters.

The selection of an insecticide was based on specific criteria: the candidate compound was required to have low toxiciEy for man and vertebrates in general and, while being very effective agalnst b1ack1y, to have as little effect as possible on non-target fauna. Only biodegradable compounds wlth 1ittIe residual activity were considered to make sure that no contamination of the environment could take place. The insecticides selected were studied by hydrobiologisEs and a fishery biologist in !{est African laboratories and in field conditions to confirm their suitability.

Because of the long life of the adult worm in the hum:n host, sufferers from onchocerciasis mny remqin infective for as long as 15 years even if not reinfected. Therefore the duration of a campaign to prevent the disease by eliminating its insect vector rmrst not be less than this length of time after the last new case in the prograrEne area. For this reason the Prograsrme is scheduled to last 20 years.

The effects of the vector control campaign on the prevalence and severity of onchocer- ci-asis must be continuously rnonitored by epideniological evaluation teams. Chemotherapy protocols should be developed for the effective and safe Ereatment of those patients so severely infected that they could become progressively blind in the next few years in spite of interruption of the disease transmission.

The Onchocerciasis Control Programe is supported by appropriately applied research projects, particularly in the fields of chemotherapy, vector control and protection of the environment. Another importanE element of the Programrne is personnel training, to ensure the progressive take over of the Prograume by specialists of the seven countries concerned. The repopulation and/or settlemenE of the uninhabited fertile areas freed from the disease is a najor objective of the Onchocerciasis Control Prograrune. Such action would also permit development measures to be taken in areas of high population density. It was anticipated that rnajor reclarnation of deserted lands would be possible some 18 months after the start of insecticide treatment in the zone concerned.

In nany cases the lands to be repopulated or colonized require infrastructure in terms of road networks, rdater supply and medical, educational and agricultural exLension services. In other instances improvement of such facilities is essential for the success of repopulation and settlement. The required low and medium level agricultural extension services in some insEances, need backstopping by professional officers in the relevant disciplines.

The nain responsibility for the economic development projects remains with each of the GovernoenEs which rnay however request external assistance in the methodology and planning of activities, and external funds for their financing. A series of reclamation plans based on the develoPment of agriculture and stock raising were studied and costed, as examples, to assist national authorities.

Launching of the Programe

The Programmp is necessarily a joint undertaking and requires the full collaboration of each of the seven countries concerned. The Programre is governed by an Operational Agreement signed at Accra on 1 November L973, which brings into association the Governments and WHO, the Executing Agency. The Operational Agreement is supplemented by separate country protocols t which establish the contributions of the Participating Governments. OCP 174.1 Rev.2 page 4

IE was decided to implement the Programe by staggering the inception of operations over a period of three years, from L974 to L976, as it would have been unrealistic to attempt to launch the vector control operations simrltaneously over such a.large area. The first phase I thus started at the beginning of the dry season in December L974, when the S. daonosum population was on the decrease, and concentrat.ed initially on a zone of heavy intestation in ttre Black Volta, Como6-L6raba, Bandam,, Nzi and Baniflng basins as a logical extension of the o1d FED/occGE campaign. The work was extended in a second phaee to the Red Volta, White Volta and Daka basins in 1975. Phase Ehree of operations, from 1976 onwards, should cover the basins of the oti-Pendjari, and of the Ma1i, Ivory Coast, Upper Volta, Niger and Benin tributaries of the Niger River.

A large-scale intercountry prograume of this nature requires the coordination of efforts at the national Ievel and the consistent support of each participating Government. To this end each of the seven Governments concerned has set up a National Onchocerciasis Corrmittee to assume responsibility for coordinaEing the technical, social, budgetary and logistic supporE of the Programme at the national level. Such national conmittees play a key role in ensuring the provision of Government counterpart contributions, the link between the Onchocerciasis ConErol Prograune itself, the repopulation and settleoent activities and projects for Ehe sub- sequenE economic development of the freed zones, and other necessary measures.

It was estimeted that the overall Progranrme would require funds in the region of some $ 120 million over a 20 year period, from 1974 to 1994. In the first insrance, derailed planning covers the six years L974-L979. The World Bank accepted to rcbilize contributions to the Progranrne and to act as the custodian of Ehe Special Fund for Onchocerciasis Control for the financing of activities. The Fund Agreement was signed on 7 l,Iay 1975 in 1{ashington, D.C.

As Execur:ing Agency, WHO assumes the technical responsibility, in conjunction with the Governments involved, for the technical and logietic managenent of the prograrn'ne. WHO appolnted a Prograurme Director who is assisted by four specialized sections Simulium Contro 1, Epidemiology and Public Health, Economic Development support and AdministraEive support). The Prograrme headquarters is located at ouagadougou, upper volta, in view of its central position in the affected area and in one of the most sorely afflicted of the seven countries invo lved.

UNDP and FAO are associated with the Programe Eo assist C,overnoenta, at their request, in planning and implementing national projects and schemes in the economic field where ext€r- na1 assistance is required to develop the zones freed of onchocerciasis.

The Steering Comittee remains as Ehe executive organ of the Programe wiEh the duty of studying and recomending the plans of work prepared by the Executing Agency.

A Joint Coordinating Comittee r^ras set up grouping the seven participating countriee, the donor nations and institutions, and the four sponsoring agenciee. The Comlttee, headed by an Independent ChairmFn meets once every year to review the aunual budget and exerclse general supervision over the Programe.

Specialists from all continents are participating in the activities of the Programe, t.hrough their contributions to and their membership of its different scientific, technlcal and advisory Eroups. Numerous scientific bodies and institutes have been collaborating ln the activities of the Progranrme since it was launched in the fields of research, training, ecology, hydrology and economic development.

?rogramme activities

The Vector Control Unit oaintains constant entomological surrr'eillance by prospection l flights and thanks to a network of 7 sectors and. 22 subgectors epread all over the programe area. Air operationg are carried out from the tlro rnaln bases at Bobo-Dioulaseo and Taua16. ocPf74.1 Rev.2 page 5

The sectors and subsectors are linked t,o one another and to the Prograume DirecEor by 17 radio transmitti.ng/receiving units. The blackfly capture points number about 3OO. The catches are counted and examined to determi.ne the morphology, physiological age and , infestation rate of the blackflies. The entonological situation is continuously evaluated.

Weekly treatment of water courses by application of insecticide is planned on the basis i of this evaluation. The rhythn of treatment is based on the biological cycle of the vector larvae. Ihe insecticide employed at present is a biodegradable organophosphorus compound, namely a 20% ernulsion concentrate of Abate. The dosages are calculated in accordance with the water flow of the rivers in the different hydrological basins; underdosages can, in fact, be just as disastrous for the proper functioning of the Programe as overdosages for nontarget fauna. The insecticide is applied from the air.

The Epidemiological Evaluation Unit carries out parasitological and ophthalmological examinations of the populations of a certain number of villages selected in advance so as to determine Ehe prevalence of onchocerciasis, as well as the endenicity and the blindness rates. Epidemiological evaluation takes place aE two levels:

(1) In all the villages selected, a basic study is conducted so as to determine the prevalence of the infection and of serious clinical symptoms, by age and sex. The following examinations are carried out: skin snips, external search for nodules and specific skin lesions, measurement of visual acuity by means of the t'hand testtrfor those who cannot read. This study is termed the ttsimplerr survey.

(2) In about lO% of the villages chosen, thorough epidemiological and clinical srudies, termed rrdetailedrr surveys are made, comprising eye examinations using the slit lamp, examination of the fundus of the eye, multiple skin snips, search for microfilariae in the rrrine , etc.

The present epidemiological evaluation comnenced in February L975 and it is hoped to complete it throughout Ehe Prograrrme area before the end of t977 so that a second evaluation of the same villages can conmence in 1978, in places where vector control has been continuing for three years. Three years of vector control are regarded as the minimal period for epidemiological evaluation of the trend of the disease.

The Economic Develop,ment Unit collects all avallable data on developent projects underwayor being prepared, at the national leve1 and the regional level, in the seven participating countries. It gives assistance to che missions concerned by this developrnent by making the necessary contacts and supplying the basic data at its disposal. It Eakes Ehe necessary action vis-A-vis the executing bodies and sources of finance.

Research is also one of the important activities of the Prograrnme. In the fields of entomology and environmental protection it deals with the eco logy of the vectors (rearing of a single generation and establishment of a laboratory colony of, S. dannosuo , cytotaxonomic and morphological studies of the S. damnosum complex, sampling of S. damnosum larvae and adults, dispersion and migration of S. damnosum adult females), with vector control (evaluation of the susceptibility of blackflies to insecticides, evaluati.on of new insecticides and formulations, biodegradability of insecticides, insecticide toxicity, equipent for insecticide application), and with protection of the environmenE (acute and long-term effects of insecticides on nontarget organisms).

LonS-term hydrobiological studies are being made on charac,teristic stretches of the watercourses treated to ensure that Ehe biological equilibrium of the rivers is not seriously disturbed by control operations. The effecEs of the insecticide on the nr:mber and distribution of S. damnosum are continuously observed so as Eo restrict treatment t.o larval breeding places actually colonized by the vecEor. Surveillance of these inportant aspects of the Progranune takes place with the participation of the Ecological Group attached to the progr:me, which gives its views on the measures to be taken in order to ensure eatisfactory environmental protection. ocPf74.1 Rev.2 page 6

Research in the medical field covers: the epideniology of onchocerciasis (studies on the dynamics of transmission of the disease and histological examination of skin lesions caused by onchocerciasis); parasitology (improvement of skin snips technique, research on other human filariases); irmunology of onchocerciasis (isolation of a purified specific ( O. volvulus anEi gen, evaluation of a fluorescent antibody test); and onchocerciasis chemo- i therapy (fieta tests of existing and new drugs, creati-on of a ChemotherapeuEic Research Centre in the Progrenme area). Research is also proceeding on the distribution of animal a onchocerciasis and the in vitro culture of microfilariae.

The Progre-me, with the assistance of specialized instituEes and bodies, is also engaged in training activities. Special att,ention is paid to the need to train nationals in the Programme area able gradually to take over the management of the Progranme itself. Theo- reEical and pract,ical training and refresher courses have been held for entomologi.sts, enEomological assistant.s and technicians. Fellowships are also provided for physicians intending Eo specialize in public health, onchocerciasis epidemiology or ophthalmology. IniEial results

The Progr:'nme is now trro years old, two years during which its establishment and its various activities have proceeded jointly, with L994 as Ehe target daEe. In order to evaluate the initial results of the work done at the present time it is important to under- stand Ehat such an evaluation should employ two differenE approaches. One is the entomological approach which is concerned with results in relat.ion to the density of blackflies, as well as their localization and their infection rates. Entorrological evaluation is continuous and provides imediate and up-to-date inforoation on the effecEiveness of vector control activities. The other is the epidemiological approach, based on examination every three years of the populations of selected villages in the zones treated.

Entomological evaluation shows that the vector density has been reduced to pracEically zero in most of the zones treated. During its two years of existence the Programue has twice been confronEed with re-invasion in certain geographically limited zones and is continuing its investigations to discover the origin of this. Generally speaking, iE is considered, howcver, that the vector control operations are now giving extremely satisfactory results and that the transmission rate has considerably dropped in most of the zones Ereated.

Subsequent epidemiological surveys will enable a definiEive appraisal of these results Eo be made.

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