Progress towards eliminating onchocerciasis in the WHO Region of the Americas: elimination of transmission in the north-east focus of the Bolivarian Republic of Venezuela.

Onchocerciasis (river blindness) is caused by the parasitic worm Onchocerca volvulus, which is transmitted by Simulium species black flies that breed in fast-flowing rivers and streams. In the human host, adult male and female O. volvulus worms become encapsulated in subcutaneous fibrous “nodules” and fertilized females produce embryonic microfilariae (mf) that migrate to the skin, where they are ingested by the black fly vectors during a blood-meal. In the vector, the microfilariae develop into the infectious L3 stage, at which time they can be transmitted to the next human host via subsequent bites. The parasite has no environmental reservoir or nonhuman hosts. Microfilariae cause severe itching and disfiguring skin disease, and may enter the eye, Progrès vers l’élimination de l’onchocercose dans la Région OMS des Amériques: élimination de la transmission dans le foyer du nord-est de la République bolivarienne du Venezuela