Health topics



Onchocerciasis – or “river blindness” – is a parasitic disease caused by the filarial worm Onchocerca volvulus transmitted to humans through repeated bites of infected blackflies (Simulium species). Onchocerciasis is an eye and skin disease. Symptoms include severe itching, disfiguring skin conditions and visual impairment, including permanent blindness.

There is no vaccine or medication to prevent infection with O. volvulus. WHO recommends treating onchocerciasis with ivermectin, an antiparasitic drug, at least once yearly for about 10 to 15 years. Where O. volvulus co-exists with Loa loa, another parasitic filarial worm that is endemic in Cameroon, Central African Republic, Congo, Democratic Republic of the Congo, Nigeria and South Sudan, it is recommended to follow the recommendations of the Mectizan Expert Committee (MEC) and African Programme for Onchocerciasis Control (APOC) for the management of severe adverse events that may occur.

Onchocerciasis occurs mainly in tropical areas. More than 99% of infected people live in 31 countries in sub-Saharan Africa. Onchocerciasis is also found in some countries of Latin America: Brazil, Guatemala, Mexico and the Bolivarian Republic of Venezuela. Efforts to control and ultimately eliminate the disease are ongoing in the African Region by APOC and in the Region of the Americas by the Onchocerciasis Elimination Program of the Americas (OEPA).

The disease is not endemic in the Western Pacific Region.