River blindness

Onchocerciasis (river blindness) is caused by infection with the fi larial parasite Onchocerca volvulus, which is transmitted by the blackfly species. The vast majority of the 37 million infected people live in West, Central and East Africa, with smaller foci in Latin America and Yemen. In addition to eye disease and blindness, onchocerciasis also causes a range of skin diseases and other systemic conditions. Currently, about 300 000 people are blind from onchocerciasis. Control measures entail larvicide spraying of blackfly breeding sites and treatment of endemic communities with the microfi laricide Mectizan® (ivermectin).

The WHO Onchocerciasis Control Programme, which operated between 1974 and 2002, covered 11 countries in West Africa (Benin, Burkina Faso, Côte d’Ivoire, Ghana, Guinea, Guinea-Bissau, Mali, Niger, Senegal, Sierra Leone and Togo). The Programme was highly effective, as by 2002 onchocerciasis was no longer a public health problem, except in Sierra Leone and some areas of Benin, Ghana, Guinea and Togo. Intense control activities will continue in these areas until the end of 2007, and surveillance is continuing in all the countries formerly covered by the Programme. Owing to civil confl ict, the status of onchocerciasis has deteriorated in Côte d’Ivoire, Guinea-Bissau and Sierra Leone.
Distribution of Mectizan® was begun in six Latin American countries in 1992 (Brazil, Colombia, Ecuador, Guatemala, Mexico and Venezuela) and in 19 African countries that had not been included in the Onchocerciasis Control Programme in 1995 (Angola, Burundi, Cameroon, Central African Republic, Chad, Congo, Democratic Republic of the Congo, Equatorial Guinea, Ethiopia, Gabon, Kenya, Liberia, Malawi, Mozambique, Nigeria, Rwanda, Sudan, Uganda and the United Republic of Tanzania). Both programmes involve partnerships between governments, nongovernmental organizations, United Nations agencies, industry and others. Mass distribution at community level is being undertaken by trained volunteers in all affected areas, except where the disease is hypoendemic (Kenya, Mozambique and Rwanda). Progress has been made in reaching the ultimate treatment goal in most of these countries, apart from Angola, Burundi, Central African Republic, Democratic Republic of the Congo and Sudan, where the therapeutic coverage is below the threshold of 65%, due mainly to political unrest. In 2006, all 13 foci in Latin America had reached a therapeutic coverage of at least 85% for the first time. To achieve therapeutic goals worldwide, distribution of Mectizan® will have to continue for longer than originally envisaged; however, the manufacturers have pledged to continue their donation of the drug for as long as it is needed.

Current situation
The disease is endemic in:

• 30 countries of Africa (Angola, Benin, Burkina Faso, Burundi, Cameroon, Central African Republic, Chad, Congo, Côte d’Ivoire, Democratic Republic of the Congo, Equatorial Guinea, Ethiopia, Gabon, Ghana, Guinea, Guinea-Bissau, Kenya, Liberia, Malawi, Mali, Mozambique, Niger, Nigeria, Rwanda, Senegal, Sierra Leone, Sudan, Togo, Uganda and the United Republic of Tanzania);
• 13 foci scattered in six Latin American countries (Brazil, Colombia, Ecuador, Guatemala, Mexico and Venezuela)
• Yemen (although ivermectin is being distributed in a few communities, technical assistance is needed to determine the current epidemiological status of the disease so that it can be controlled).