An outbreak of abortion in mares associated with Salmonella abortusequi infection.

An abortion outbreak occurred in a herd of 38 horses, 26 of which were pregnant mares. Twenty-one mares aborted between 5-10 months of gestation. In no case were there indications of impending abortion. Pathoanatomical, histopathological, virological and bacteriological examinations were carried out on 4 aborted fetuses. Histopathology identified Gram-negative bacteria compatible with salmonella in all 4 placentae. By subsequent bacteriological examination Salmonella abortusequi was isolated as the single causative agent in each case. Nonmotile Salmonella abortusequi with antigenic formula 4,12:-:- was isolated from one of the 4 fetuses. The described episode of equine abortion clearly indicates that Salmonella abortusequi has not been eradicated from Europe as previously thought.