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infection with worms of the genus Onchocerca. Human infection is caused by O. volvulus, with heavy infestations usually being characterized by subcutaneous nodules (onchocercomas) containing tangled masses of adult worms, a persistent dermatitis, lymphadenitis, and ocular lesions related to the invasion and death of microfilariae, which may progress to optic neuritis, optic atrophy, and blindness. The condition is also known by many local and regional names (craw-craw, Robles' disease) and by various names descriptive of the manifestations of the disease (coast erysipelas, river blindness, blinding filarial disease).
Infection with Onchocerca (especially O. volvulus, a filarial nematode transmitted from person to person by black flies of the genus Simulium), marked by nodular swellings forming a fibrous cyst enveloping the coiled parasites (onchocercoma); microfilariae move freely out of the nodule and escape into the intercellular lymph in the dermis. Dermatologic changes often develop in those affected, especially in patients in Africa, resulting in intense pruritus, scaly or lichenoid skin, depigmentation, and destruction of elastic fibers. Most important are the ocular complications that may develop after a long chronic course, with blindness frequently occurring in advanced cases, caused by the presence of living or dead microfilariae seen by slitlamp biomicroscopy.
onchocerciasis/on·cho·cer·ci·a·sis/ (-ser-ki´ah-sis) infection by nematodes of the genus Onchocerca. Parasites invade the skin, subcutaneous tissues, and other parts of the body, producing fibrous nodules; blindness occurs after ocular invasion.
Any of several diseases caused by infestation with filarial worms of the genus Onchocerca, especially a disease of humans caused by O. volvulus and characterized by nodular swellings on the skin and eye lesions that can result in blindness. Transmitted by black flies of the genus Simulium, the disease occurs in tropical regions of Africa and Central and South America. Also called river blindness.
Etymology: 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. 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. Treatment is diethylcarbamazine for the microfilariae and surgical excision of nodules to remove adult worms. Protective clothing and control of black flies with DDT are the best preventives. Ivermectin is used to treat this condition. Also called river blindness.
onchocerciasis(ong?ko-ser?ki'a-sis) (-sez?) plural.onchocerciases [ Onchocerca + -iasis]
Infection with Onchocerca volvulus.Synonym: onchocercosis; river blindness See: illustrationillustration
onchocerciasisA tropical parasitic disease, mainly of West Africa, caused by the microfilarial worm Onchocerca volvulus . The filarial forms of the worm are spread by the biting blackfly Simulium damnosum , which breeds only in turbulent rivers-hence the alternative term river blindness. Onchocerciasis causes lumps or nodules under the skin, each containing at least one male and one female adult worm. After impregnation, the female worm releases millions of microscopic microfilaria which migrate under the skin and enter the eyes where, on dying they set up a severe and destructive inflammation that leads to irremediable blindness. The microfilaria also often block lymph channels and cause ELEPHANTIASIS. Treatment is with drugs such as diethylcarbamazine and suramin to kill the worms. This may cause severe reactions.
Parasitic infestation caused by filamentous worms of the genus Onchocerca, especially O. volvulus, that is found in tropical America and is transmitted by several types of blackflies.
Mentioned in: Antihelminthic Drugs
A disease caused by infestation with the filarial worm (Onchocerca volvulus) spread by blackflies. It is common in tropical Africa and Central America, especially in areas near rivers. Large numbers of microfilariae are present on the skin and often enter the eye. The patient initially complains of itching, but blindness occurs as a result of chorioretinitis and optic neuritis. The disease is treated successfully with ivermectin. Syn. onchocercosis; river blindness.
infestation by the filarioid worm Onchocerca spp.; can cause a variety of diseases listed generally under the heading of onchocercosis.