Etiologic agents detected in a 10-year study of bovine abortions and stillbirths.

During a 10-year period, specimens from 8,995 bovine abortions were submitted to the South Dakota Animal Disease Research and Diagnostic Laboratory; 8,962 of these specimens were suitable for examination. A supportable diagnosis was made in 2,942 (32.82%) of the abortions examined. An infectious cause was determined for 2,723 (30.38%) and a noninfectious cause for 219 (2.44%). Bacteria caused 1,299 (14.49%), viruses caused 948 (10.57%), and fungi caused 476 (5.31%). The infectious bovine rhinotracheitis virus was associated with 485 (5.41%) and the bovine viral diarrhea virus with 407 (4.54%). The most common noninfectious causes of abortion or stillbirth were anomalous development, 112 (1.25%); dystocia, 56 (0.62%); and twinning, 37 (0.41%). The cause of 6,020 (67.17%) abortions was not determined. Lesions, many suggesting the presence of infection, were present in 1,554 (17.34%) fetuses or placentas in which no infectious agent could be demonstrated.