Onchocerca Health Dictionary

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Onchocerca: From 1 Different Sources

n. a genus of parasitic worms (see filaria) occurring in central Africa and central America. The adult worms are found in fibrous nodules within the connective tissues beneath the skin and their presence causes disease (see onchocerciasis). Various species of black fly, in which Onchocerca undergoes part of its development, transmit the infective larvae to humans.
Health Source: Oxford | Concise Colour Medical Dictionary
Author: Jonathan Law, Elizabeth Martin

Onchocerciasis

(Syn. “river blindness”) A. disease caused by the parasitic filarial nematode Onchocerca volvulus. (See also filariasis).... onchocerciasis

Filariasis

The term used to describe several clinical entities caused by one or other of the nematode ?lariae; these include Wuchereria bancrofti/Brugia malayi, Onchocerca volvulus, Loa loa, Dracunculus medinensis (DRACONTIASIS or guinea-worm disease), Mansonella perstans, etc. These organisms have widely di?ering geographical distributions. Whereas lymphatic ?lariasis is present throughout much of the tropics and subtropics, ONCHOCERCIASIS (river-blindness) is largely con?ned to west and central Africa and southern America. Loaiasis is an infection of west and central Africa, and dracontiasis involves west and central Africa and western India only.

Clinically, the lymphatic ?lariases characteristically cause ELEPHANTIASIS (lymphoedema); onchocerciasis gives rise to ophthalmic complications (river-blindness), rashes and subcutaneous nodules; loaiasis causes subcutaneous ‘Calabar swellings’ and subconjunctival involvement; and dracontiasis predisposes to secondary bacterial infections (usually involving the lower limbs). Diagnosis is by ?nding the relevant ?larial nematode, either in blood (day and night ?lms should be examined), or in one or other of the body ?uids. An EOSINOPHILIA is often present in peripheral blood. Serological diagnosis is also of value. In onchocerciasis, skin-snips and the Mazotti reaction are valuable adjuncts to diagnosis.

The mainstay of chemotherapy consists of diethylcarbamazine (aimed predominantly at the larval stage of the parasite). However, ivermectin (not available in the UK) is e?ective in onchocerciasis, and metronidazole or one of the benzimidazole compounds have limited value in dracontiasis. Suramin has been used to kill adult ?larial worms. Prevention consists of eradication of the relevant insect vector.... filariasis

Filaria

n. (pl. filariae) any of the long threadlike nematode worms that, as adults, are parasites of human connective and lymphatic tissues capable of causing disease. They include the genera *Brugia, *Loa, *Onchocerca, and *Wuchereria. Filariae differ from the intestinal nematodes (see hookworm) in that they undergo part of their development in the body of a bloodsucking insect, e.g. a mosquito, on which they subsequently depend for their transmission to another human host. See also microfilaria. —filarial adj.... filaria

Nematode

(roundworm) n. any one of a large group of worms having an unsegmented cylindrical body, tapering at both ends. This distinguishes nematodes from other *helminths. Nematodes occur either as free-living forms in the sea, fresh water, and soil or as parasites of plants, animals, and humans. *Hookworms and *threadworms infest the alimentary canal. *Filariae are found in the lymphatic tissues. The *guinea worm and *Onchocerca affect connective tissue. Some nematodes (e.g. threadworms) are transmitted from host to host by the ingestion of eggs; others (e.g. *Wuchereria) by the bite of a bloodsucking insect.... nematode

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