Loiasis is a disease caused by the filarial parasite Loa loa. It is characterized by transient localized swelling as the adult worm migrates in the subcutaneous tissues. The worms may also transit the eye beneath the conjunctiva. Humans and monkeys may be common hosts to certain species of the parasite.
Loiasis is highly endemic in tropical (equatorial) west and central Africa. It is limited in distribution to forest areas in Central Africa from eastern Nigeria to Angola, extending into Congo, Zaire, Uganda and the Sudan. In Ethiopia a similar disease is called Kampala eye worm. In the Congo River basin, in particular, up to 90 percent of villagers in some areas are infected. In total it is believed that loiasis affects about one million people.