Dermatology and Internal Medicine, Wilford Hall Medical Center, Lackland AFB, Texas, USA.
Onchocerciasis is a common, chronic multisystem disease with dermatologic, ocular, and systemic manifestations. Although the disease is endemic in Africa, Latin America, and Yemen, imported cases have been described in the United States. The causative organism, Onchocerca volvulus, is transmitted by the bite of a black fly of the genus Simulium. There are a number of cutaneous manifestations of the disease, including onchocercomas, which are subcutaneous bundles of worms. The antiparasitic agent ivermectin is the drug of choice for both prophylaxis and treatment of active disease.