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*In November 1999 the World Health Organisation announced that the parasite had been eliminated from a wide area of West Africa, preventing the potential infection of nearly 12 million children and saving 100,000 people at immediate risk of blindness. Over 1.25 million people have been cured of their onchocercal infection. Equally important, removing this threat has allowed the farming of 25 million hectares which had been abandoned because of the black fly. The complete programme will end about 2002.

Onchocerciasis, or "river blindness," is caused by the filarial nematode, Onchocerca volvulus. After lymphatic filariasis, it is the second commonest filarial infection in man. The clinical findings were first described in 1875 and the adult worms were reported at a meeting in 1891 (Leuckart). In 1904 Brumpt recognized that the infection occurred most commonly along river banks and that the microfilariae in the skin came from the deeper cutaneous nodules in which there were adult filariae. He also noted that there were no microfilariae in the blood. It was not until 1972 that Neafie gave a detailed description of the adult male and female worms. Onchocerciasis is perhaps even more devastating than other filariases since this chronic disease is a major cause of blindness worldwide.


River blindness. Whitewater disease. Blinding filarial disease. Sowda (Arabia). Galfilarienne and craw craw (Africa). Sp: Erisipela de la costa (Guatemala). Infermedad de Robles. Mal morado (Mexico). Ceguera de los rios (Africa). Fr: Onchocerque. Ger: Onchozerkafilarie. Krauelfilariae.


Onchocerciasis is a parasitic disease caused by the filarial worm Onchocerca volvulus.

Geographic Distribution

There are 15-20 million people throughout the world infected by 0. volvulus (Fig. 26.21). Like many other diseases in developing countries, accurate statistics on prevalence are difficult to obtain. The vast majority of cases, perhaps 96%, are from Africa in a band through the mid-equatorial region of the continent from west to east. West Africa has the largest burden of disease, about 30% of the global cases. In 1994 WHO estimated there were 1.2 million people infected in Uganda, 40 times more than the previous estimate made 7 years earlier. In equatorial Guinea there were 60,000 cases. But in the last few years the eradication program in West Africa has been so successful that it is hoped that this infection will disappear from that region in the next decade. Central America has the next greatest prevalence, with small foci in northern South America (Mexico, Guatemala, Venezuela, and Colombia). There is also infection in Saudi Arabia and Yemen. Onchocerciasis can be so devastating that fertile valleys are abandoned and the economic development of countries has been affected.

Fig. 26.21. The geographic distribution of onchecerciasis. It is hoped that this disease will decrease during the next decade, and perhaps even disappear.

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Copyright: Palmer and Reeder