What Is River Blindness?

River blindness is an eye and skin disease caused by a tiny worm called onchocerca volvulus, which is spread by the bite of an infected blackfly. These flies breed in fast-flowing streams and rivers, hence the name river blindness. People with severe infections will usually have dermatitis, eye lesions, and/or subcutaneous nodules. Blindness is almost always inevitable for those with severe infections. The disease spreads from person to person by the bite of a blackfly. When a blackfly bites a person who has river blindness, microscopic worms (called microfilariae) in the infected person's skin infect the blackfly. The microfilariae develop over two weeks to a stage where they are infectious to humans. When an infectious blackfly goes on to bite another person, it will typically inject one or two larvae along with its bite, thus transmitting the disease to the person. Since the worms can only increase their numbers in humans by first mating and then cycling their microfilariae ...