Bovine viral diarrhea virus (BVD) infection is responsible for a variety of economically important syndromes in beef herds. The economic losses from BVD infection will vary between herds based on herd immunity and stage of gestation at the time of exposure, the virulence of the BVD strain and other factors.
BVD CONSULT provides bovine veterinarians with an opportunity to consult with their clients and develop BVD prevention and control programs for any cow-calf herd. The virus is known to cause immune suppression, respiratory disease, infertility and fetal infection. Fetal infection (infection of the fetus during pregnancy) can lead to early embryonic death, abortion, birth defects, stunting, or the birth of persistently infected (PI) calves. Persistently infected cattle can result when susceptible pregnant cows are exposed to BVD virus during the first half of gestation and the virus passes from the dam to the fetus. Many times infected fetuses are aborted, but if a PI fetus survives to term, it will always have a tremendous amount of the virus in its body and cannot mount an immune response to clear the virus. A PI animal will secrete BVD virus throughout its life; in contrast to animals that become infected after birth that secrete the virus and are contagious for a few days to two weeks. These PI calves constitute the main reservoir and source of BVD virus for spread within the herd and to other herds of cattle.
Cattle persistently infected with BVD virus can be identified by a number of laboratory tests. Based on the NAHMS 2007-08 Beef Cow-calf study, while only 8.8% of U.S. cow-calf ranches had one or more PI animals identified; this means that one in every 11 to 12 herds have PI calves and most are not aware of their presence.
Vaccination programs can provide fairly good protection against BVD-induced disease when the exposure is from non-PI animals that are transiently infected with BVD. Vaccination programs offer some (but decreased) protection against BVD-induced disease when the exposure is from PI animals because of the tremendous amount of virus excreted by PI animals. Vaccination programs are an important component in BVD control, but will only offer a high level of protection if herd contact with PI animals is eliminated.
The cattle industry has made significant efforts in recent years to control BVD based on research that has provided a more complete understanding of the epidemiology of BVD, enhanced availability of diagnostic tests for detecting animals PI cattle, and a better idea of the economic impact BVD has on cattle herds. Our current knowledge of the epidemiology of BVD, the availability of efficacious vaccines, and the improvement in diagnostic tools have made the control of BVD feasible.