Onchocerciasis Onchocerciasis, commonly known as “river blindness”, is caused by the parasitic worm Onchocerca volvulus. The parasite is spread and transmitted to humans by the repeated bites of infected blackflies that breed in rapidly flowing rivers. Symptoms include severe itching, disfiguring skin conditions, and visual impairment, including permanent blindness. The disease primarily affects rural populations in sub-Saharan Africa, and Yemen, with smaller endemic areas foci found in parts of