River blindness (Onchocerciasis) is a disease caused by infection with the parasitic worm Onchocerca volvulus. The parasite is spread by the bites of a black fly that lives near rivers and many bites are usually required for infection.

Signs and symptoms

Symptoms include severe itching, bumps under the skin, and blindness. Skin involvement typically consists of intense itching, swelling, and inflammation with severe rashes permanently damaging patches of skin.


Ivermectin (Mectizan®) is used to paralyse and kill microfilariae which relieves the intense skin itching and halting the progression towards blindness. It also prevents adult worms from reproducing for a few months following treatment and so reduces transmission. A single dose of ivermectin needs to be taken annually to be effective.