PRESENCE OF BOVINE LEUKEMIA VIRUS IN COLOSTRUM SAMPLES AND ITS POTENTIAL TO INFECT NEWBORN CALVES

Abstract

Bovine leukemia virus (BLV) is a retroviral agent that primarily affects dairy cattle. Colostrum is the main source of immunoglobulins for calves; however, it is also a vehicle for the vertical transmission of BLV. The aim of this work was to determine the presence of BLV in colostrum and its potential to infect newborn calves. Seven mothers and their seven daughter calves were evaluated. Blood, colostrum, and milk samples were taken. An ELISA was performed to detect BLV in blood, colostrum and milk serums. Furthermore, a PCR test (env gene) was used for BLV detection in blood and colostrum. An identity analysis was used (phylogeny) to verify the origin of the sequences obtained from the DNA of mothers, calves, and colostrum. Six of the seven cows were positive for BLV by ELISA, while five of them were positive by PCR. None of the calves was positive by PCR at birth. However, the BLV provirus was found in two calves on day 15 and in one calf on day 30. The identity of the sequences was confirmed as BLV. Colostrum and milk are vehicles for the vertical transmission of BLV, which explains that three of the seven calves evaluated showed BLV infection during the early postpartum period.