EQUINE VIRAL ARTERITIS IN NEWBORN FOALS - CLINICAL, PATHOLOGICAL, SEROLOGICAL, MICROBIOLOGICAL AND IMMUNOHISTOCHEMICAL OBSERVATIONS

Clinical, pathological, immunohistochemical, serological and microbiol ogical findings are described for 2 geographically and temporally dist inct equine arteritis virus (EAV) epidemics in newborn foals. Outbreak ii occurred at a commercial Standardbred breeding facility; Outbreak B began in a group of research animals. Clinical signs were severe and primarily referrable to the respiratory tract. Fever and leucopenia a nd/or thrombocytopenia were observed in foals surviving for more than 24 h. The most common gross pathological findings were limited to the respiratory tract. Common histopathological findings included intersti tial pneumonia, lymphocytic arteritis and periarteritis with fibrinoid necrosis of the tunica media. Renal tubular necrosis was noted in 2 f oals. Immunoperoxidase histochemistry combined with virus isolation wa s diagnostic in all cases.