Fetal infection with bovine leukemia virus in sheep.

Several sheep fetuses were thymectomized, and their tails were removed at 58 to 65 days of gestation for tissue culture. Bovine leukemia virus (BLV) antigens were detected in serial culture of tissues from fetuses whose dams and sires were both BLV positive. However, no BLV antigens were detected in serial cultures of tissues from fetuses whose dams were negative but whose sire was positive. Precolostral serums from 3 of 16 neonatal lambs, whose sire and dams were both BLV positive, were BLV antibody positive. Thus, BLV may be vertically transmitted from a positive dam to her lamb via the placenta and/or germinal cells but not from sire to lamb.