Onchocerciasis Control Programme (OCP): Success of 28 years of disease control in West Africa

December 04, 2002

Onchocerciasis - "river blindness"
Before the OCP got under way, onchocerciasis was the second cause of infection-induced blindness in the world. It was affecting 36 countries in Africa, the Yemen and, very locally, Latin America. But the most severely hit was Africa where it was a debilitating obstacle to settlement and economic and social development.

The disease is called "river blindness" because of the damage it causes in its most severe stages and because its vector, a blackfly (Simulium species complex) of the simulid family, develops in swift-flowing rivers. It is brought on by a parasitic nematode worm, whose larvae (microfilarians) seriously damage eyes and skin in humans. About 120 million people were at risk from river blindness, 96 % of them in Africa. As many as 18 million people were suffering and had skin lesions, 99 % of them in Africa. Six and a half million people infected suffered from severe itching or dermatitis and 270 000 lost their sight. (Source: WHO)

The Onchocerciasis Control Program in West Africa (OCP)
The OCP, the first far-reaching programme to be set up to fight onchocerciasis, will cease its operations this month, December 2002. Launched in 1974, it was sponsored by the WHO, responsible for its implementation, the World Bank, charged with mobilizing and administering funds, the UNDP and the FAO. It benefited from the support of 22 countries (including France) and donor organizations.

No applicable medicine was available for mass control campaigns at first. The OCP's initial method consisted in interrupting the cycle of transmission and eliminating the blackfly larvae -by aerial spraying of biodegradable insecticides into fast-flowing reaches of rivers in 11 West African countries. In 1987 an additional weapon, the drug ivermectin, began to be administered. It destroys the microfilarians and inhibits reproduction in adult filarian worms. Up to 50 000 km of rivers irrigating 1.3 million km2 were treated every week.

The OCP has achieved its goal. River blindness has been practically eliminated from the areas covered, where it is no longer either a public health problem or an obstacle to economic and social development. In this way, 300 000 cases of blindness have been avoided and 11 million children born in this area since the OCP's launch have been spared the risk. Fertile land bordering rivers, amounting to 25 million hectares, has been given over to cultivation and pastoral agriculture. And the ecological outcome is reassuring. Hydrobiologists found that the insecticides deployed have never had any irreversible effects on aquatic ecosystems (scientific bulletin n°137, 2001) or -of particular concern for their economic significance- on fish.

The OCP has moreover been a catalyst in the training and setting-up of national teams of specialists who are maintaining and will maintain both onchocerciasis surveillance and control and monitoring of the aquatic ecosystem in their countries.

IRD and river blindness control
From 1956, medical entomologists from the IRD (ORSTOM at the time) have conducted studies on the life-cycle and ecology of the parasite's vector in West Africa. Then, from 1961, they successfully carried out insecticide-spraying campaigns against it. That work gathered substantial amounts of key entomological and epidemiological data. These proved crucial for determining the principles of strategy and defining the measures to be adopted for vector control, the only feasible method at the time for fighting the disease.

The results attained enabled researchers to propose a regional-scale control project and to play a decisive role in devising the OCP, in designing its operational and evaluation structures, and in promoting awareness among the funding organizations.

IRD entomologists worked in relays, practically without interruption, to run the OCP vector control campaigns . This they did from 1974 to 1998, the year they handed over to one of their African colleagues who trained with the OCP.

The entomologists from the IRD (ORSTOM at the time) of the Institut Pierre Richet at Bouaké worked, until the end of the 1980s, on the genetic characterization of the vector species complex. They improved knowledge about their life-cycle and ecology, methods for monitoring the effectiveness of the insecticides and entomological and epidemiological assessment methods. Their action was decisive in studying and preventing any reinvasion of the areas that had been disinfected, and for detecting and dealing with cases of insecticide resistance.

At the same time, a sizeable team of IRD hydrobiologists, based at Bouaké for ten years, then at Bamako, collected a wealth of fundamental original data on ecological communities of water courses in Africa. They defined the methods and standards to be adopted for surveillance of West-African aquatic ecosystems and organized a system involving a network of national technicians trained by them.

The hydrologists from the IRD also played an important role. They helped develop and renovate national networks for river-flow measurement, essential for gauging the right insecticide doses.

Medical parasitologists contributed in effecting epidemiological surveys to delimit the OCP zones to be treated, They also took part in defining the tools to be used and the standards to be adopted for epidemiological surveillance. Finally they participated in the evaluation of ivermectin for mass campaigns and in follow-up impact assessment of this agent in the area of the APOC programme which was on the point of being set up (African Programme for Onchocerciasis Control) (scientific bulletin n°6, 1996).

Demographers and geographers have contributed to establishing the relations between human settlement patterns and the degree of gravity of the disease. They originated the first calculations which gave evidence of the economic benefit of the first years of treatment. A team of social sciences researchers accomplished a multidisciplinary enquiry which produced economic justification for extending the zone covered by the OCP at the beginning of the 1980s.

A former director-general of the IRD (ORSTOM at the time), Professor Guy Camus, was Chairman of the OCP's Scientific Council, Jean Mouchet chaired the Expert Advisory Committee for many years and several IRD researchers have successively been members of that committee, of the APOC equivalent and of the OCP Ecology Group, chaired for a long period by Christian Lévêque.

Two films on the disease and the campaign have also come from the IRD, who co-produced them with the French Ministry of Overseas Development and WHO. Entitled, Mara, le Regard du Lion, 1985 and Les Yeux de l'Espoir, 1997, they were intended to draw the attention of funding organizations.

From OCP to APOC (African Programme for Onchocerciasis Control), the fight goes on The remarkable success the OCP had had in 11 African countries, for public health, the economy and development, served to justify the launch of a new programme, APOC: the African Programme for Onchocerciasis Control. Started in 1995 for a planned duration of 12 years, its objective is to put in place sustainable systems for distributing ivermectin (by local communities themselves) to 50 million people in 19 countries which were not covered by the OCP. Finally, APOC has an additional feature over the already well-performing OCP; it demonstrates that this kind of partnership can bring a lasting solution to a problem which is simultaneously one of public health and of development.

Institut de recherche pour le développement

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