Onchocerciasis, or River Blindness, is caused by the parasitic worm Onchocerca volvulus. It is transmitted through repeated bites by blackflies of the genus Simulium. The disease is called River Blindness because the blackfly that transmits the infection lives and breeds near fast-flowing streams and rivers and the infection can result in permanent blindness. In addition to visual impairment or blindness, onchocerciasis causes skin disease, including nodules under the skin causing constant, severe itching. Worldwide, onchocerciasis is second only to trachoma as an infectious cause of blindness. WHO expert committee on onchocerciasis estimates that at least 25 million people are infected and 123 million people live in areas that put them at risk of infection.
The fight against river blindness relies on mass administration of over 100 million annual doses of ivermectin, a de-worming drug with an exceptional safety record, except in the case of co-infection with Loa loa, where the necrotic embryos can lead to a life-threatening inflammatory response. The international community, including governments, NGOs, and leading pharmaceutical companies, has launched an extraordinary public health program to combat onchocerciasis and its causative pathogen, Onchocerca volvulus.