onchocercosis

onchocercosis

the diseases caused by infection with the nematodes Onchocerca spp. The presence of large numbers of microfilariae in the skin is associated with a severe, summer dermatitis called also wahi, kasen in cattle and summer mange or allergic dermatitis in horses. See also sweet itch.

An association is suspected between periodic ophthalmia in horses and onchocerciasis because of the finding of microfilariae in the eye and because Onchocerca volvulus is a known cause of blindness in humans.

The adult worms cause little problem to the animals but the hides and carcasses are damaged and reduced in value. The relationship between the worms and the occurrence of fistulous withers, poll evil and tendonitis is unproven. The lesions in the aorta caused by O. armillata are often extensive but appear to cause little clinical disease.