When a female blackfly bites an infected person during a blood meal, it also ingests microfilariae which develop further in the blackfly and are then transmitted to the next human host during subsequent bites.
Armed with biodegradable larvicides, insecticides that kill larvae, fleets of helicopters, small planes, and trucks launched an offensive against the blackfly, the carrier of the disease.
Between 1974 and 2002, disease caused by onchocerciasis was brought under control in West Africa through the work of the Onchocerciasis Control Programme (OCP), using mainly the spraying of insecticides against blackfly larvae (vector control) by helicopters and airplanes.