Causes of bovine abortion in the North-Central United States

Abstract

During 1983-2001, a total of 1618 aborted fetuses from farms with multiple abortions were examined to determine the cause. A specific cause was determined in 592 (36.59%) cases. Infectious agents associated with inflammatory reaction were detected in 435 (26.88%) cases. Bacterial abortions were identified as the most common infectious cause of abortion, 265 (16.38%) cases, with Arcanobacterium pyogenes being the most frequently isolated bacterium. Viral causes of abortion were diagnosed in 77 (4.76%) cases, protozoal in 55 (3.39%) cases, and 38 (2.34%) of the cases were diagnosed as mycotic abortion. There were also 65 (4.01%) cases of congenital myopathy and/or cardiomyopathy, 12 (0.74%) cases of congenital renal oxalosis and 38 (2.34%) cases of multiple congenital malformations. Lesions suggestive of infection were present in 157 (9.70%) fetuses or placentas in which no infectious organisms were identified. The cause of 873 (53.96%) abortions was not determined. Serological examination of 590 single or paired serum samples from aborting dams was of little diagnostic value for bovine viral diarrhoea (BVD), infectious bovine rhinotracheitis (IBR) and leptospiral abortions. Five serum samples from aborting dams (38 examined) had high Neospora caninum antibody titres (800-12?800). Aborted fetuses from these dams had encephalitis and myocarditis. Serological examination of thoracic fluid from 80 fetuses was of little diagnostic value for IBR, BVD, Neospora sp., Toxoplasma sp. and leptospiral abortions.