Social and economic importance of onchocerciasis

EXPERT COMMITTEE ON EPIDEMIOLOGY OF ONCHOCERCIASIS Geneva, 1O-18 November 1975 Draft agenda item 5.4 SOCIAI AI{D E@NOMIC IMPORTANCE OF ONCHOCERCIASIS by F. S6ri6 Directorate-General of Public Health Ministry of Public llealth and the Population Abidjan, Ivory Coast Health was long considered as a gift of heaven, a private asset. However, the concept of health has greatly changed since science cornmenced t,o advance; it is no longer the concern of a single individual but is now regarded as a public asset and therefore an economi-c and social investnent factor. The prevention of contagious illness, which consists in Protecting a large number of members of the comunit,y against the major endemic diseases, constitutes a human investment, factor. iiowadays, both in the developed countries and in the young countries of Africa, Asia and Latin America, health has become a part of social and economic development. It ensures that a large reserve of physical and intellectual manpower is available to improve the national economy. Public health is no longer considered solely as a mental attitude or a philosophical or religious concept, for, in the African sountries, it is the concern of all. Itris is indeed the case of onchocerciasis or river blindness, a disease which hampers the development of rich lands and has become a matter for economists. 1. ONCTIOCERCIASIS AND fi{E AFRTCAN COUNTRTES During half a century of penetration and occupation of Africa by Europe the colonizers had to fight not only against an unhealthy climate but also against very murderous epidemic diseases such as yellow fever, plague, smallpox, trypanosomiasis, etc. A11 the researches of the Pasteur Institutes and all health activities had a single aim: the eradication of these dreaded scourges. Onchocerciasis existed of course at that time. It was described for the first time in 1895 but it did not represent a threat even if it was responsible for river blindness. rrWhat do the bLind begging in the streets of the large towns rnatter? In comparison with trypanosomiasis this is not an urgent problem ...rr 1.1 Why is this disease so much discussed? Why are there so many meetings and conferences devoted Eo onchocerciasis? After the Second World War the different African colonies were occuPied with the Political problems of decolonization which 1ed to their total emancipation. Next came the setting up of the WORLD HEALTH ORGANIZATION ORGANISATION MONDIALE DE LA SANTE oNclro/wP/75.1 ORIGINAL: FRENCH Ce document ne constrtue pas une publication. ll ne doit farre I'objet d'aucun compte rendu ou r6sumd ni d'aucune citation sans l'autorisation de l'Organrsation Mondiale de la Sant6. Les oprnions exprimdes dans les articles signCs n'engagent que leurs auteurs. 'i 1 i I The issue of this document does not constitute formal publication. lt should not be reviewed, abstracted or quoted without the agreement of the World Health Organrzation. Authors alone are responsible for views expressed in signed articles. 0NcH0/wP/75.1 Page 2 administrative and political structures of the different, states. As the recurring financialburdens become more and more enornous it became necessary to give thought Eo the economy and, above all, to the feeding of the population. In the Ivory Coast as in the other African countries, agricultural development has become urgent and is even a priority for the Ivory Coast Government so that henceforward. the naEional economy is centred on agriculture. The south, the forest region, is developing at an extraordinary rate. Ttre towns are overpopulated. The north, on the contrary, is losing its population and the exodus is becoming a mFtter of concern. Something had to be done to slow down the departure of the young people and prevent them leaving their lands empty and this led to Ehe northern development pro3lct('rOp6ration du Grand Nord"). However, the success of this great agricultural pro5ettinvolving 75o million US dollars is governed by a single condition: the disappearance of onchocerciasis, for that disease is the great obstacle in the way of development of the northernIvory Coast. 1.2 llow does onchocercia sis han4igap the development of the north? VIhat social and economic importance can be assigned to it? This study is restricted intentionally to the Ivory Coast Republic, where the blackfly and onchocerciasis threaten to change Ehe socioeconomic character of a basically agricultural country. The effects of onchocerciasis and Simulium are the same in the Sudanese savanna countries. 2. ONCIIOCERCIASIS IS A SCOURGE The filaria, the pathogenic agent of the disease, and the blackfly Simulium damnosuo, thevectorofLhemicrofi1aria,constituteaveritab1esocia1andeconomi."ffitries concerned. To understand the extent, of this scourge, a distinction must be made between trwo cytotypes of Simulium damnosum the savanna cytotype, which is prevarent in the north of the country and Lhe forest cytotyPe, in the south. Both.these cytotypes are found in Lhe IvoryCoast. 2.L Savanna onchocerciasis: a redoubtable social scou rge 2.L.L Part plaved by the filaria The north and part of the centre of the country are in the grip of onchocerciasis. victims show the following serious clinical signs: - skin symptons of filarial pruritus; Ihe eye symptoms with a high incidence of blindness. inhabitanLs are blind; physical debility of onchocerciasis sufferersl premature aging of the population. In some villages, 2O to 25% of Et.e Ihe prevalence of onchocerciasis in these regions 45 to fu% it children. is very high: 90 to 100% in adults; Ihe longevity of an adult filaria is 10 to 20 years. The sufferer generally carriesthree to six worms (sometimes more) so that survival in the definitive host is ensured and consequently he will be exposed all his life, if he does not, leave the hyperendemic area, tothe effects of the filariae responsible for filarial pruritus and eye troubles. oNcrro/wP/75.1 PaSe 3 2.L.2 Role of Simulium Blackflies bite by day, particularly when the sky is overcast and in shady places. The bite itself (below the knee) is not much felt at first, but rapidly becomes itchy and finally constitutes a nuisance which a large number of bites renders intolerable. During the rainy season, i.e. the moment suitable for growing crops in Ehe va11eys, an individual may be bitten in the course of the day by several blackflies, even as many as 3OOO, rendering all hunan activity Practically impossible, since there is no place for the vicEim, except during the night. I{hen the blackfly does not find victims in the fields it can fIy scores of kilomet,res to bite them in the villages. 2.1.3 What is the reaction of the population to eye troubles and nuisance caused by blackflies? The first reaction of the population is to flee from the malefic influence of the river spirit who is making them blind, for the inhabitants of these areas long believed in Ehe powers of some evil spirit. It was only later on, following health education and the developmenE of schools in the counEryside, that many villagers understood the part played by Simulium and microfilariae in blindness. At present the population has left the river banks. It has abandoned the fertile valleys and settled on plaEeaux or on hillsides as was proved when visits rrere made by helicopter or airplane to the onchocerciasis control prograrnme zones in the Volta River Basin area.I Large exPanses of arable land, whole plains, are uninhabited. On travelling along the northern part of the Ivory Coast rivers and through the Volta rivers region no villages are tobe seen bordering on watercourses, whereas in the south of the country, in the forest, villageIife is lived in Ehe inrmediate neighbourhood of the rivers; in the north, the village fields are far from the valleys. 2.L.4 Socio consequ ences of onchocerciasis in the savanna Many tropical diseases v*rich affect a large number of persons can influence the regional economy. In the case of onchocerciasis the scourge is accompanied by seri.ous demographic, social and economic disturbances: flight of young and healthy workers to the lower Ivory Coast, thus abandoning the agedto their sad fate; Upper Volta is losing its young people to the advantage of theforest areas of the Ivory Coast and Ghana; disturbed populat,ion balance: in a village in the Korhogo area there are more rromen than men (lOO women and 55 men); the persons encountered in the village are helplessinvalids (2O-W% of them are blind); it is a picture of desolation, ,itt nore o1dpeople than young ones; .t"r{"Ih:$o the concentration of the population on ttre plareau (So-160 inhabirants perkm') following the desertion of the fertile valleys is leading to the parcelling out and impoverishment of the arable land, which is over-exploited as a result of permanent cultivation, finally resulting in degradation of the soil. 1 - Progranrne fj-nanced by UNDP and carried out by WIto with the participar,ion of FAo and thecooPeration of IBRD. Regions of the Ivory Coast and of six other West African countries areincluded in this programme. oNcHo /wP / 7 5. 1 Page 4 Consequences. The yields are tradit,ionally low; the virlage fields amount to ress than two hectares Per Person. Moreover, productivity is very seriously impaired by the pitilessdrought that has continued for five successive years. The rural urarkets are less and 1essfrequented and traditional crops are disappearing. Travelling merchant,s are becoming rare since there is no longer any trade. A11 this is bringing about the economic death of a region becauseincome. The chief victims of onchocerciasis, i.e. the blind, come to charity. This is contrary to rvory coast tradition, and to alleviate of the blind the state is at presenE constructing, with the aid of the national institute for education of the blind. of the farmersr lack of the south to ask for the difficult situation Swiss Government, a 2.L.5 ,The area affected by onchocerciasis in the Ivory Coast covers nearly 80 OOO kmz with more than a million-and-a-ha1f inhabitants. Income per head is the lowest in the Ivory Coast, varying from 2OOO to SOOO francs CFA or nine to 37 US$ (annual net monetary income). It is thus comparable to that of the neighbouring countries covered by the progranme for oncho- cerciasis control in the Volta River Basin area. This area is one that is potentially rich from the agricultural viewpoint but poor because of lack of development. As concerns EheLraditional crops iE is estimated that the loss of earnings suffered by the peasants in the northern region amounts to more than five million us dollars per year. ![hat socioeconomic advantages can the Ivory Coast hope from the onchocerciasis control plgrgramre? Apart from interruPtion of the disease, which alone is sufficient to justify Ehe prograure,blackfly control will render better socioeconomic development of the north of the Ivory Coastpossible. Ihe development of this part of the counrry ca11s for preliminary destruction of the vector agent of onchocerciasis. Ihe disappearance of the blackfly from the river valleys will have considerable repercussions on a number of development projects already underway in the north. These projects, such as sugar cane production at Ferkess6dougou, irrigated rice fields in the neighbourhood of Korhogo (visited by participants in the Conference of the Joint Coordinating Cormittee in Abidjan) will be rescued and successfully completed. If no action had been planned against Simulium the great sugar-producing project in the region would certainly not have come about. These projects were developed following the sur,aIl scale FED-OCCGE onchocerciasis control campaign. In the absence of the present regional prograEme, entomologists forecast that workers in the sugar cane fields would stay there for not rnore than 10 years before deserting the Ferkess6dougou area because of the invasion of blackflies and the appearance of initial eye sympEoms, and this would sive rise to a manpoT^7er criSiS with the closing of the factory and all its sociaL and economic consequences. Generally speaking, this anti-blackfly campaign will free nearly a quarter of the national territory from the grip of Simulium and lead to the reclaiming of fertile land for cultivation, pasturage and reforestation, in brief, for implementing agropastoral or agroindustrial projects evaluated at 7fr roillion US$, 275 millions of which are already earmarked for the development of the Korhogo, Ferkess6dougou, Katiola and Odienne regions. The Ministry of the Plan estimates the area which can be used for traditional crops to be lOO OOO hectares, for the west bank of the White Bandama and the banks of the Bou, which are practically uninhabited, could take 11 OOO Senufo peasant families from the Korhogo area. Seventy-five settlement villages are envisaged and this will lead to an extension of the social infrasLructure, i1e. roads, health cent,res, and 25O wells for drinking water supply. oNcrlo /wP/75. 1 Page 5 In the Niankaramandougou area (valley of the White fi,andama) nearly 5OO families can be settled. Sociological studies show that the Senufo population would be willing to emigrate to this uninhabited area where 5OO OO0 hectares of fertile land could be oade available to Ehem. As can be seen, the economic recovery of the area will be rapid. Already an Ivory Coast I'linistry of Agriculture has been set upr 4 National Directorate for the coordination of State development societies and of regional socioeconomic development directorates. The emigration of Senufo population groups will be semi-directed and carefully prepared, but non-compulsory. In this connexi.on the Ministry of the Plan has just set up an independent society, the Rural Promotion Office, with a view to encouraging emigration to new green spaces in the prograune area, nrmely San Pedro and Kossou. 2.2 0nchocerciasis in the forest zone: a redoubtable economj.c scourge 2.2.L 1964 epidemiological survey In 1964 an epidemiological survey made by the National },l.ajor Enderoic Dj-seases Service all over the country revealed for the first time the presence of onchocerciasis in the forest zone, along the following rivers and their tributaries: Como6, llhite Bandarna, NZi, Red Bandama, Sassandra and Cavally. Findings: (a) no onchocerciasis in dense forest; example: south-west of the country, San Pedro region (Lower Cavalty - Lower Sassandra); (b) high endemicity all along the Como6 River, except at the coast; (c) no onchocerciasis on the coast, i.e. to the south of the rivers; (d) presence of onchocerciasis in industrial crop areas; (e) forest onchocerciasis is not as serious as in the northern savanna region; in the Tiassal6 and Abengourou region, there is massj-ve infection with a prevalence rate of 8O%in adults atd 20% in children; although prevalence is high from the microfilarial viewpoint, clinical signs with eye symptoms are rare (very few blind persons); (f) the blackfly nuisance is considerable, particularly during the rainy season wtren the number of bites per man and per day may exceed 5OOO, which seriously handicaps any human activity; examples: economic death of Tiassal6 (I{hite Band"-a) and Bettie (lower Cono6); Present difficulties in completing the work on the Tiassal6-Taabo dam on the White Bandrme because of the rrassive invasion of the work area by blackflies, so that the responsible officials of the rrBandama Valley Authorityr' (BVA) have asked for the assistance of IfIIO(meeting held on 2O June 1975 in Bouake, with the entomologists of the Ouagadougou Regional Programe). 2.2.2 Onchocerciasis and exploitation of the forests A11 entomologists are unanimous in stating that the forest represents a fuI obstacle against the propasation and long distance flight of blackflies. Thus the forest is an imPortant factor acting against the presence of Simulium. An example which may be given is that surveys in the lower Caval1y, lower Sassandra and the San Pedro area, in brief all the south-wesE, have not revealed any breeding places or blackfly larvae. This zone is sti1lfree from any sign of onchocerciasis. On the other hand, to Ehe north and in the centre of these waLercours high endemicity. es where the forest has given way to coffee or cacao planta tions. there is 0NcH0/wP/75.1 Page 6 In the case of the Cono6 and the Bia where there are no longer any forests (cacao plantation and timber exploitation for nearly 5O years) the disease is found from Ayam6 and A16p6 right to the north, with more than 5O% endemicity in the Bettie region. The same applies at Tiassa16, where there is no longer any forest. The fate of Tiassal6 is now the same as that of Bettie: economic death. The coastal regions would be affected if the seaweeds did not prevent the spread of theblackfly towards Lhe coast. Conclusion. Forests must therefore be protected, particularly the scheduled ones which act as a barrier to the development of onchocerciasis. If this warning is not heeded in the south of the country then, before the commencement of the nexE century, there is a risk that Ivory Coast agriculture will have died. The blackfly nuisance in forest areas near rivers wiIl be such that all human activities will become impossible. 2.3 Role of dams in the po.ssible spread of onchoc erciasis in the lvory Coast The construcLion of dams for the development of certain areas, particularly dams for agricultural PurPoses in the tropics, has seriously upset ecological conditions. In some countries dams have helped to bring about diseases such as trypanosomiasis, malaria, schistosomiasis, onchocerciasis, etc. In the Ivory Coast there are two dams which give rise to some concern as regards the spread of onchocerciasis: (a) The Ayam6 dam on the Bia was put into service in 1959. Ihe riverine population of the Bia, particularly downstream from the dam, who previously seemed to be unaffected, now have an infection rate of 15%. (b) The Kossou dam this dam with a large impounding reservoir measuring several km2, will gradually drown the blackfly breeding places upstream. In other words the siEuation upstream from Lhe dam will improve considerably all along the reservoir, with the di earance of and I term cure of onchocerciasis sufferers since they will no longer be reinfected (Beoumi On the contrary, downstream from the dam, from thejunction of the two Bandamas (White and Red) as far as Tiassal6, breeding places have developed and the situation i-s worse (example: blackfly invasion in Tiassal6). The Presence of ur,any breeding places irmnediately after the dam has already been reported. Consequences: (1) Upstream large dams create a large lake which drowns the breeding places but downstream they produce a rapid spillway which promotes the development of blackfly larvae. (2) Smal1 locaI dams for agricultural purposes do not slow dom the current sufficiently uPstream and accelerate it downstream. The result is multiplication of blackfly breeding places and abandonment of the land by the peasants (exarnple: Ayam6). Consequently engineers and economists are no Ionger entitled to ignore these facts and should consult an epidemiologist before erecting a dam. 3. CONCLUSION Because of its socioeconomic consequences, onchocerciasis plays an important part in the development of the African countries and handicaps our progress. It takes over large expanses of fertile land useful for human activities and disorganizes social life in northern Ivory coast where it gives rise to serious clinical s)rmptoms, with blindness. In forest regions the blackfly nuisance prevents any human activity. It has already brought about the economic death of the Tiassal6 and Bettie DepartmenLs - regions where theforest has been completely devastated by forestry undertakings and cacao and coffee planters since 1924. oNcrro/}IP/75.1 Page 7 Onchocerciasis is definitely a redoubtable social and economic scourge for the young countries south of the Sahara. ST'MMARY The author shows in his paper that public health is now a factor in the development of the young countries of Africa, the Americas and Asia. It is for Ehis reason that, economists and the World Bank are interested in onchocerciasis control in the Volta River Basin area. The author is an Ivory Coast citizen and describes the social and economic consequences of river blindness in his country - the Ivory Coast: (a) In the savanna i.e. the north of the country, onchocerciasis is very serious, with unny victims who are blind. The plains have been abandoned for Ehe plateaux, the river banks are deserted, the north is emigrating to the south. (b) In the forest i.e. the south, there are very few clinical symptoms. Cases of blindness are rare, but blackfly bites prevent any human activity (5000-6000 bites per dayper man). Deforestation and exploitation of the forest favour blackfly invasion. The forest is an obstacle to the propagation of these insecEs. * , ) ri 't r '}i i i t