Investigation of pregnancy losses in beef cattle herds associated with Neospora sp. infection.

There are many potential causes of abortion and fetal wastage in beef cattle; all can result in significant economic losses to the producer. Determination of the etiology is fundamental to developing recommendations regarding abortion control and prevention. Since it was first described as a cause of bovine abortion in New Mexico in 1987 (1), infection with Neospora sp. has emerged as a significant bovine reproductive disease. It is one of the most commonly diagnosed causes of bovine abortion in California (2), and has been identified worldwide (3). Although most reports of significant numbers of abortions due to Neospora have been associated with dairy cattle (1,2,4,5), Neospora congenital infections and abortions have also been documented in beef cattle (6). This report presents the epidemiological and clinical observations of 2 beef herds with outbreaks of pregnancy loss associated with Neospora sp. infection. The 2 herds involved were located in the Peace River district of British Columbia, but were separated by more than 100 km and had no contact with each other. Herd A consisted of approximately 100 commercial Simmental and Charolais cows, while herd B consisted of approximately 165 purebred and commercial Simmental cows. Both herds were vaccinated annually with a multivalent clostridial vaccine, a 4-way respiratory virus vaccine (Infectious Bovine Rhinotracheitis, Parainfluenza-3, Bovine Respiratory Syncytial Virus, Bovine Virus Diarrhea), and an Escherichia coli bacterin. Lasalocid sodium was included in the mineral salt as a coccidiostat from February to May. The owner of herd A had purchased 3 bred heifers in the fall of 1993 and 2 bulls in the spring of 1994, while there had been no recent additions to herd B. The 1994 calving season