onchocerciasis /ong′kōsərkī″əsis, sī″əsis/ [Gk, onkos, swelling, kerkos, tail, osis, condition] , a form of filariasis common in Central and South America and Africa, characterized by subcutaneous nodules, pruritic rash, and eye lesions. It is transmitted by the bites of black flies that deposit Onchocerca volvulus microfilariae under the skin. Also called river blindness. ▪ OBSERVATIONS: The microfilariae migrate to the subcutaneous tissue and eyes, and fibrous nodules form around the developing adult worms. Hypersensitive reactions to the dying microfilariae include extreme pruritus, a cellulitis-like rash, lichenification, depigmentation, and rarely, elephantiasis. Involvement of the eye may include keratitis, iridocyclitis, and rarely, blindness from choroidoretinitis. Diagnosis is made by demonstrating microfilariae by skin biopsy or in the eye by slit lamp. ▪ INTERVENTIONS: Treatment is diethylcarbamazine for the microfilariae and surgical excision of nodules to remove adult worms. The broad-spectrum antiparasitic drug ivermectin is also used for treatment. ▪ PATIENT CARE CONSIDERATIONS: Protective clothing and control of black flies are the best preventives.
