Histopathological and Immunofluorescent Studies on the Uterus of Aborted Mares Experimentally Infectedwith Equine Arteritis Virus

Two pregnant mares, at 5 and 6 months gestation were inoculated intranasally with the Bucyrus strain of equine arteritis virus (EAV). Both mares aborted at 1 1 days after the inoculation. Multi focal and necrotizing myometritis was found histopathologically in the uterus. Large numbers o f mononuclear cells had infiltrated the smooth muscle and interstitium o f the myometrium. The smooth muscle cells showed signs o f degeneration with sarcoplasmic vacuolation, and necrosis with acidophilic sarcoplasm and pyknosis or karyorrhexis. EAV antigens were detected in the smooth muscle cells o f the myometrium. These findings suggested that a replication o f EAV had occurred in the smooth muscle cells o f the uterus, resulting in the myometritis.