Onchocerciasis(redirected from Onchochersiasis)
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a chronic parasitic disease that is caused by nematodes of the genus Onchocerca. Onchocerciasis occurs universally and mainly affects ungulates; the greatest economic damage arises when cattle and horses are affected. The intermediate hosts of Onchocerca are simuliids and ceratopogonids, which are bloodsucking insects. The infestation is most prevalent in pastures during the swarming time of the intermediate hosts. The mature parasites concentrate in the tendons, ligaments, and connective tissue, causing inflammatory foci that are often aggravated by pyogenic microflora.
Onchocerciasis usually occurs without observable symptoms. Diagnosis in the living animal is based on the presence of Onchocerca larvae in skin biopsies and on the results of allergic skin tests. No specific treatment is available. Onchocerciasis is prevented by protecting animals from the bites of simuliids and ceratopogonids and by exterminating these insects during hatching time, from May to August.