An Electron Microscopic Investigation of Bovine Abortion

Bovine abortion continues to cause economic loss to farmers and ranchers. In South Dakota, monetary loss from bovine abortion has been estimated at 4 to 4.8 million dollars annually. (31) Brucellosis was once considered the major cause of bovine abortion. Since the prevalence of brucellosis has been reduced to less than 1% of the total United States cattle population, there has been an increase in demand for laboratory assistance in the diagnosis of the causes of bovine abortion. With the present day technology in microbiology, histology, and serology, a confirmed identification of the causative agent of bovine abortion can be made in only 30%-40% of cases examined. Results of serologic and histologic examinations seem to indicate infection occurs in numerous cases in which no etiologic agent can be identified. The search continues for methods which would increase the accuracy of laboratory diagnosis of the causes of bovine abortion. Negative stain electron microscopy (EM) has been used to demonstrate viral structures in infected cell cultures, feces, and other clinical material. This technique was applied to lung and liver tissue extracts obtained from 500 aborted or stillborn calves submitted for diagnostic purposes to the South Dakota Animal Disease Research and Diagnostic Laboratory. The following goals were set for the project: 1. To determine if this technique can be used on fetal tissue to identify known etiologic agents of bovine abortion and compare results with those obtained by conventional techniques. 2. To determine if viral agents not detected by conventional means are present in tissues of aborted calves. 3. To attempt to isolate and identify any agents found, and 4. to determine if this technique has application in the routine diagnosis of bovine abortion