Impact of bovine viral diarrhea virus on reproductive performance in cattle.

The major economic impact of BVDV infections is in producing reproductive dysfunctions. The virus can have a detrimental impact on the developing fetus at all stages, but the most severe consequences occur early in gestation. The virus is maintained in the bovine population through the production of PI offspring. Only the NCB biotype of the virus can produce PI calves. The NCB biotypes is the one that produces the vast majority of BVDV infections and, as a consequence, the greatest economic losses. Biotype and antigenic variation are two independent variables and vaccines should emphasise antigenic composition, not biotype. A BVDV control program that does not emphasize heifers is doomed to failure.