If the dam is immune to the exposing strain, the virus is eliminated and no infection occurs in the fetus. However, if the dam's immunity is insufficient to prevent fetal infection by a particular strain or if she happens to be persistently infected with the virus, then several things can happen. First 4 Months of Pregnancy A. Early embryonic death. Increased open cows and late calvers may occur. This is one of the least studied aspects of BVDV infection and the extent of the problem is not known.
More research is needed to identify the true impacts of early embryonic losses.
With BVDV, abortions can occur at any stage of pregnancy, even months after initial infection. The earlier in the course of gestation these infections occur, the greater the diagnostic challenge. Virus cultures may be negative simply because the virus has done damage but is no longer present for culturing. Calves may be delivered full term, either dead or weak. D. Persistently Infected Calves.