Once a person is infected, the parasite migrates to all internal tissue of the eye except the lens, causing eye inflammation, bleeding, and other complications that lead to blindness.

How does onchocerciasis cause blindness?

You can develop river blindness if you're bitten repeatedly by infected female blackflies. The blackfly passes the larvae of the worm Onchocercidae through the bite. The larvae move to the subcutaneous tissue of your skin, and mature into adult worms over 6 to 12 months.

How is river blindness caused?

Onchocerciasis is an infection caused by the parasitic worm Onchocerca volvulus, spread by the bite of an infected Simulium blackfly. It is also called river blindness because the fly that transmits infection breeds in rapidly flowing streams, mostly near remote rural villages, and the disease that is caused by O.