Bovine Virus Diarrhea Virus (BVDV) infection in cattle herds can result in major economic loss from poor reproductive performance (reduced percent pregnant, increased abortion and stillbirth) or poor calf performance (increased calf sickness and death loss). Cattle persistently infected with BVDV (BVD-PI) are the primary reservoir for BVDV infection in cattle herds, and thus are the major focus of control programs.
Most BVDV infection problems in cattle herds go unnoticed since 70-90% of BVD infections do not result in observable disease. When present, the most common disease caused by BVD virus infection in cattle herds is
poor reproductive performance including, abortions, poor conception rates, stillbirths, and weak calves. In addition, BVD virus infection causes suppression of the bovine immune system resulting in increased susceptibility to other infectious diseases. In cow-calf herds the immunosuppressive effect of BVD is normally noticed as increased calf death loss (from scours and pneumonia) and poor weaning weight. In feedlot animals this is noticed primarily as increased death loss and incidence of respiratory disease (pneumonia). Lastly, BVD virus infection alone can cause diarrhea with oral ulcers and bleeding disorders.
Note that a cow can be PI, but NEVER show signs! They even suggest testing cows that lose a calf, if the calf did not get tested when born dead. This stuff is not something to mess with.
Not saying this is what is going on, just doing a public service announcement since someone else brought it up
