Onchocerciasis control in Benin: achievements and prospects after OCP

F! ONCHOCERCIASIS CONTROL IN BENIN Achievements and Prospects after OCP 2002 1 ,I INTRODUCTION 1.1 Onchocerciasis in West Africa before OCP ' Onchocerciasis prevails in Africa, America and in the Arabian peninsula. ' It was estimated that in the world: Approximately 122,9 million people are exposed to onchocerciasis. More than 17,7 million people were infected with the disease. More than270 000 people were blind and at least 500,000 had visual impairment cased by onchocerciasis. Africa is the continent most affected, with more than 16.9 million (95%) victims. West Africa was not only particularly affected but most of all it had the most significant foci of the most serious form of the disease. These foci were located particularly in the northem parts of Benin, Togo, COte d'Ivoire, Ghana, east of Mali, the south of Niger and were disseminated in the whole of Burkina Faso. It is in these areas known as the original area, covering 654,000km2 that the Onchocerciasis Control Programme in West Africa (OCP) was started. The Programme then extended to the foci south of C6te d'Ivoire, Benin, Togo and Ghana, then to the west of Mali, Guinea, Guinea-Bissau, Senegal and Sierra Leone. Today, the whole of the Programme area covers | 235 000 km2 with almost 40 million people. Before the beginning of the control operations, there existed more than 3 million onchocercal patients out of which approximately 135,000 were blind. Onchocerciasis is a parasitic disease. It is caused by a filarial (a worm) known as Onchocerca volvulus. The adult worrn which develops only in man produces microfilariae which is transmitted to other men by the bite of a tiny fly commonly called "simulie", the vector of the disease. Onchocerciasis prevails only in rural areas, in the settlements located along the rivers with fast flowing current. The simulie reproduces in these rivers, hence the name "river blindness" which is still interchanged with the name onchocerciasis. The most exposed communities are those located approximately ten kilometres on both sides of the rivers. Blindness, the nuissance and other consequences of onchocerciasis are factors for the deterioration of the living conditions of these communities and the cause of the abandonment of the fertile riverain lands by the villagers. I r I An agreement signed in 1973 between the participating governments and wHo defined the limits, the objectives, the of consultative structures and management of the Programme as well as the modalities for control operations and evaluation procedures. After approval of the mission report of the "support Programme to Governments" in January 1974, the budget necessary for the implementation of the onchocerciasis control programme in the Volta basin was voted. WHO was then designated as the Executing Agency. In a fit of international solidarity, 22 countries and institutions financed the activities of OCP for nearly three decades. 2 tr 1.2. Control Strateeies used The main strategy used is vector control to which ivermectin treatment was added in 1987. In certain areas, vector control was the method used and in others ivermectin treatment only. In some others on the other hand, the two strategies were combined. 1.3. Results obtained in the OCP area Onchocerciasis is now eliminated as a problem of public health in all the OCP area. In some limited foci however, there is the need to improve on the results achieved. Nearly 40 million people are protected today from onchocerciasis and more than 18 million children born since the beginning of the Programme have escaped the risk of onchocercal blindness. I 600,000 cases ofblindness have been prevented Presently, more than 25 million hectares of riverain lands have been redeemed and is being re-populated and developed. This will enable about 17 million people to be nourished. It is to be noted however that, at some points, the results need to be improved. These are the tributaries of the Oti in Togo, the Ou6m6 in Benin, the Pru in Ghana, the Mafou and the Tinkisso in Guinea. II ONCHOCERCIASIS IN BENIN 2.1 Onchocerciasis in Benin before OCP . Benin is one of the first seven countries of the Programme. . Before the launching of control activities, the country was a highly onchocerciasis endemic zone, especially in its northern part with prevalence varying from 25.5%o to 84.2% and the Community Microfilarial Load (CMFL) varying between 2.27 and 36.83 MF by biopsy. . Annual Potential Transmission (APT) was between 0 and 1,398 while the Annual Biting Rate (ABR) was between 8 and 29,205. UI. CONTROL STRATEGIES USED 3.1. Vector Control . It is based on rotational insecticide larviciding. . Control began in 1977 (phase III of OCP operations) and covered the basins north of the country, namely, Alibori, Sota, M6krou and Pendjari. . In February 1988 it was extended towards the south on the basins of the Ou6m6, the Okpara, the Zou and the Mono. r J ,\ 3.2. IvermectinTreatment ' Ivermectin was introduced in 1988 in the basins of Benin (K6ran, Perma, Yerpao, Kara, Ou6m6, Okpara, Zou, Kouffo and Mono). . From 1988 to 1997 treatment was done by mobiles teams (health workers). ' Since 1998 treatment is done by the communities themselves and has involved more than 2800 endemic villages. 3.3. Training To ensure the maintenance of the achievements of the Programme by the Participating Countries, OCP undertook the academic and on-the-job training of the nationals particularly in control strategies. 3.4. Other stratesies Information, Education and Communication (IEC), epidemiological and entomological surveillance also constitute strategies for the control of the disease. IV. RESULTS IN 2OO2 4.1. On the epidemioloeical level The results are very satisfactory in all the basins. In2002 out of 60 villages evaluated 52 (87 %) had prevalences of between 0 and 5 % (objective < to 5 %). The prevalence passed from 59 to 1,1 oZ on the Niger and its tributaries, from 70 to ll o/o on the Okpara, 72,4 to 1,8 o/o on the Zou. On the Mono and the Ou6m6 in spite of prevalences of around 20 to 30 % in certain villages one notes a tendency of regression. The Community Microfilarial Loads (CMFL) are quasi nil everywhere (standard < 1). 4.2. On the entomolosical level The Annual Transmission Potential (ATP) passed from 2313 to 107 at the Alibori capturing point in Alibori, from712 to 57 in K6r6mou in M6krou and from 538 to 0 in F6r6kire in Sota. (objective < 100). Some minor pockets of transmission persist: M'B6t6koukou on the Ou6m6 where the Annual Transmission Potential passed from 5206 to 867 between 1988 and 2001 and of Atch6rigb6 where it passed from 6147 to 72 during the same period. 4.3. Ivermectin Treatment (CDTI) The objective is to treat 100% of the villages and at least 65Yo of the population of each eligible village. In 2001, the geographic coverage was 81,3o/o (2594 villages treated out of 3194) and the therapeutic coverage 77,7oh (l 017 867 people treated out of 1 310 661 listed). It should be noted that the coverage rates are improving year by year. 4 4.4. In the field of training On the whole 60 people in Benin underwent training through OCP sponsorship, namely, 12 in entomology, 13 in public health, 12 in ophthalmology, 12 in management of the health services, 04 in epidemiology, 04 in parasitology and 03 in hydrobiology. The doctors, nurses just as the Community distributors of the endemic zones were trained in onchocerciasis control strategies. V OBSERVATIONS Strengths Significant reduction in the prevalence, the incidence, the CMFL, the number of blind and finally of the annual transmission potential. National executives trained in various fields: public health, epidemiology, entomology, management etc... Obvious political commitment and a clear implication of the communities in the control of onchocerciasis. The future Multidisease Surveillance Centre (MDSC) in Ouagadougou could be an operational structure of concertation among the Participating Countries after 2002. Weaknesses Persistence of some capturing points in the Ou6m6 basin presenting completely unsatisfactory results. CDTI Geographic coverage remains lower than the objective set in certain villages and health centres. Insufficient financing and materials for the decentralised structures, for the implementation and follow-up of activities, particularly for health centres of the sub-prefectures. vI. CONDITIONS TO SUSTAIN AND IMPROVE ACHIEVEMENTS To have an effective supply system of the needed quantities of ivermectin (given freely by MDP) for the endemic villages To treat 100% of the endemic villages regularly and at least 65% of the population in each village by continuing the CDTI reinforcement actions already undertaken and also by the implementation of the stringent measures. Making available to the decentralised structures financial and material means sufficient for their activities. Regular monitoring of the activities, continuation and intensification of the sensitisation of the populations in order to guarantee their best involvement. Epidemiological and entomological surveillance aimed at monitoring the evolution of trends and to detect a possible recrudescence of the disease. With this intention, the national prograrnme of onchocerciasis control in Benin must have the trained personnel as well as the adequate material and financial means. 5