Whether or not BVDV has a role in bovine respiratory disease has been controversial, but the majority of evidence suggests that BVDV contributes to bovine respiratory disease through its immunosuppressive effects on the host. Although there have been conflicting findings, it does appear under some circumstances that venereal infections with BVDV transiently decrease conception rates. The adverse effect on conception has been attributed to fertilization failure. BVDV Infection in Immunocompetent, Pregnant Cattle BVDV infections in immunocompetent, pregnant cattle result in clinical manifestations in the dam similar to those previously described. An additional outcome of BVDV infection in pregnant cattle is the potential for transplacental spread of the virus to the fetus.
Transplacental infection is common and occurs with high efficiency.
The principle determinant of the outcome of fetal infection is gestational age of the fetus at the time transplacental infection occurs. Embryonic Death, Abortions and Stillbirths. BVDV infection after insemination can result in significant embryo-fetal loss because such infections are detrimental to early embryonic development. Trans- placental infection of the fetus between 50 and 100 days of gestation may result in fetal death. Expulsion of the fetus may occur from days up to several months after fetal infection.