Onchocerciasis (river blindness) is a parasitic disease caused by infection with the nematode Onchocerca volvulus. This disease is the world’s second-leading infectious cause of blindness. Transmitted to humans through the bite of a black fly of the genus Simulium, the larval nematodes spread throughout the body. When the worms die, their Wolbachia symbionts are released, triggering a host immune system response that can cause severe itching, and can destroy the optical tissue in the eye.
Onchocerciasis can be controlled through spraying blackfly breeding sites with insecticide and community-wide mass drug administration of Ivermectinin in affected areas. When treated early, blindness can be avoided.