Situation and trends
Onchocerciasis is caused by infection with a filarial nematode (Onchocerca volvulus) transmitted by infected blackflies (Simulium spp.) that breed in fast-flowing rivers and streams. The adult worms produce embryonic microfilarial larvae that migrate to the skin, eyes and other organs. Although most onchocerciasis cases occur in sub-Saharan Africa, the infection also occurs in Yemen and four out of six original endemic countries in Latin America (the Bolivarian Republic of Venezuela, Brazil, Guatemala and Mexico).
In Africa, the Onchocerciasis Control Programme in West Africa (OCP) operated from 1974 to 2002. The African Programme for Onchocerciasis Control (APOC) started in 1995 and targets endemic countries that were not covered by the OCP. During the year 2014, 22 countries reported that more than 112 million people were treated with ivermectin.
The Onchocerciasis Elimination Program of the Americas (OEPA) was launched in 1992 under the Pan American Health Organization (PAHO) Directing Council resolutions CD48.R12 and CD49.R19 with the goal of interrupting onchocerciasis transmission in six endemic countries in Latin America by 2015. Columbia and Ecuador have been verified by WHO and declared free of onchocerciasis by end of 2014. In 2014, Brazil and the Bolivarian Republic of Venezuela treated about 20 thousand people with ivermectin.