Onchocerciasis, also known as river blindness, is a disease caused by a parasitic worm called Onchocerca volvulus. This worm is transmitted to humans through the bites of infected blackflies, which are commonly found near fast-flowing rivers. The infection can lead to severe itching, skin rashes, and in some cases, vision loss or blindness. The disease is most prevalent in certain regions of Africa, Latin America, and Yemen. Efforts to control onchocerciasis include the use of medications like ivermectin, which help reduce the number of worms in the body. Community health programs also play a crucial role in raising awareness and preventing the spread of the disease.