Stephanofilaria stilesi

General Description: Small nematodes, up to 8.5mm in length.

Life Cycle: Unknown; thought to be indirect. The horn fly, Haematobia irritans, is the intermediate host of Stephanofilaria stilesi in the United States. In Australia the buffalo fly, Haematobia irritans exigua is believed to be the intermediate host.

Geographical Distribution: Distribution limited to North America, Hawaii, Canada, U.S.S.R, and tropical Australia.

Significance: Animals tend to rub lesions, making them worse. Skins of carcasses are unfit for sale.

Effect on Host: Worms live in outer layers of skin, causing inflammation and destruction of hair follicles and skin glands. Raised areas or papules develop, from which fluid and blood may ooze. Papules join to make large lesions which may reach 25cm in diameter. Itching causes the host to rub the lesions, aggravating them. Hair loss can result.

Diagnostic Information: Larvae or microfilariae may be found in tissue near the lesion.

Control: Controls horn flies and buffalo flies. Protect cattle from flies. Treat lesions with ointment.

Lesion on udder of cow caused by Stephanofilaria		Skin lesions – S. stilesi