Seroepidemiological evidence for horizontal transmission of bovine C-type virus

Thirty colostrum-deprived calves from leukemia-free herds were foster nursed for 10 weeks on cows infected with bovine C-type virus (BLV) from multiple-case herds or on cows from leukemia-free herds. After weaning, the calves were raised in continuous contact with BLV-infected animals of approximately the same ages. Sera collected at 6 to 18 and 43 to 48 months of age were examined for the presence of antibodies to BLV by the immunofluorescent antibody test. At 6 to 18 months of age, only 1 of the 30 calves from leukemia-free herds had a detectable antibody response to BLV. By 43 to 48 months of age the number of antibody-positive animals had risen to 17. The foster dam's herd of origin did not significantly affect the rate of BLV infection. These results indicate that BLV can be horizontally transmitted from infected to noninfected animals.