Viruses, bacteria, and diet are all reasons for a cow to abort. BVD, or Bovine Virus Diarrhea, is a disease that is difficult to treat or prevent.
Vaccinations protect cows, but defending fetuses against infection is difficult.
Maintaining a closed herd is the best prevention. It is also important to keep submitting samples to get a diagnosis. The virus is very difficult to isolate. The placenta is the most important tissue to submit for diagnosis. If a sample lacks this important tissue, chances for diagnosis decrease by about 50 percent.