- STEPHANOFILARIA STILESI
- Armed Forces Institute of Pathology
- This classic lesion of cattle of the Southern US is more about the vector than the filarid parasite. The vector is the horn fly, a fly whose large numbers that feed on the underside of the cattle in huge numbers. The horn fly causes millions if not billions of dollars in ecnomic loss due to the irritation, lost wieight gain, milk etc. it causes in cattle across the US. It also is the vector of Stephanofilarisis. These lesions on the underside of cattle, often near the umbilicus is the result of mild dermatitis and exudation which draws the flies. Females live in cystic hair follicles, and larvae live in the dermis (where they can easily be ingested by horn flies during a blood meal.) Both cause minimal inflamamtion, but if the adults move into the dermis, a significant eosinophilic reaction results, and the horn flies like the areas of inflamed, alopecic flesh. Over time, repeated bites in this area cause plaque-like areas of granulation tissue, and ultimately fibrosis in older cattle.