ONCHOCERCIASIS

Onchocerciasis is the result of infection by the filarial Onchocerca volvulus.The infection is conveyed by flies of the genus .The flies breed in rapid flowing, well-aerated water, the larvae being attached to rocks or crabs. Infective larvae are introduced in the skin by the bite of an infected Simulium fly. Innumerable microfilaria discharged by the female O.volvulus more actively in these nodules and in the adjacent tissues ,are widely distributed in the skin and may invade the skin. The infection may remain for months or years .The first symptom is usually itching, localized to one quadrant of the body and later becoming generalized and involving the eyes. This is difficult to see on the dark skin, in which the most common signs are chronic changes of a rough, thickened or inelastic skin. Eye disease is most common in highly endemic areas and in associated with chronic heavy infection and nodules on the head. Early manifestations like itching, lacrimation, conjunctival infection. The findings of nodules or characteristic lesions of the skin or eyes in a patient from an endemic area are suggestive. Filarial antibodies may be detected in up to 95 percent of patients, but antibody positivity can be lower in highly infected expatriates. Mass treatment in a single dose kills microfilariae and prevents their return for 9 months. Simulium can be destroyed in its larval stage by the application of insecticide to streams. Long trousers, skirts and sleeves discourage the fly from biting.