What organism causes river blindness?

The organism that causes river blindness is Onchocerca volvulus. This parasitic worm is transmitted to humans through the bites of blackflies from the genus Simulium. Once inside the host, the adult worms reside in subcutaneous nodules known as onchocercomas, where they can live for many years. The disease, known as onchocerciasis, can lead to severe itching, skin lesions, and ultimately, vision impairment or blindness due to the inflammatory response triggered by the worm's microfilariae migrating through the eye.

In contrast, the other organisms listed cause different diseases. Wuchereria bancrofti is responsible for lymphatic filariasis, Trypanosoma brucei is the causative agent of African sleeping sickness, and Plasmodium falciparum leads to malaria. Each of these parasites has its unique transmission route, life cycle, and clinical manifestations, which distinctly separate them from the pathogenesis associated with Onchocerca volvulus and river blindness.