Effect of bluetongue virus on reproduction in sheep and cattle.

Bluetongue virus (BTV) has been shown to be arbortigenic and teratogenic. After transmission of BTV under natural and experimental conditions the consequences of vertical transmission in pregnant sheep or cattle are variable. Factors that influence reproductive consequences are the stage of gestation, characteristics of the virus, source and concentration of virus inoculum, placentation, season and the method and route of infection. Reproductive consequences vary greatly in degree but in general include infertility, abortion, mummification of the fetus, stillbirths and congenital anomalies and dysfunctions in the live offspring. Immunological unresponsiveness, sporadic viremia and development of "late disease" were consequences of vertical transmission in offspring of infected cattle. Perpetuation of BTV through 3 generations in cattle was documented. The presence of BTV in semen of infected bulls has been demonstrated.