EN
The applicability of the polymerase chain reaction (PCR) for the detection of proviral DNA of BLV in newborn calves was tested. Out of 22 calves from BLV infected mothers, studied during first 3 weeks after birth, 13 were serologically positive by ELISA. However, only 3 calves were positive for BL V provirus in their blood leukocytes’ DNA. Since the serological test can not discriminate active infection from colostral immunity, detection of proviral DNA by PCR could be recommended for early diagnosis of BLV in newborn calves.