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, mostly near remote rural villages. The infection can result in visual impairment and sometimes blindness. Additionally, onchocerciasis can cause skin disease, including intense itching, rashes, or nodules under the skin. 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: WHOexternal icon, DPDx, CDC