Onchocerciasis, or River Blindness, is a Neglected Tropical Disease (NTD) 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 blindness. In addition to visual impairment or blindness, onchocerciasis causes skin disease, including nodules under the skin or debilitating itching. Worldwide onchocerciasis is second only to trachoma as an infectious cause of blindness.
Image: Left/Right: Blackflies, the vector of onchocerciasis. Center: Microfilariae of O. volvulus from a skin nodule of a patient from Zambia, stained with H&E. Image taken at 1000x oil magnification. Credit: WHO, DPDx, CDC