2022 Volume 75 Issue 6 Pages e114-e121
The eradication of bovine leukemia virus (BLV) in a dairy farm with high prevalence was demonstrated. The risk of BLV transmission was classified based on the proviral load (PVL) in peripheral blood and the bovine MHC (BoLA) class II DRB3 alleles of infected cows, and cows with high PVL were preferentially removed. In addition, to reduce the frequency of intrauterine infection, in principle, female sexed semen was artificially inseminated into uninfected cows. Furthermore, release milking cows into the paddock was discontinued, and infected milking cows in the dairy barn were absolutely segregated with infected cows with resistance-related alleles placed at the border with the uninfected cows. Five of the calves born to 11 infected cows were infected, and the frequency was higher in high PVL cows. October 2015, when the BLV prevalence in the milking herd was the highest at 82.8%, measures against BLV were initiated, and eradication was finally achieved in May 2020. In combination with control of intrauterine infection, the removal of high PVL cattle and the segregation of infected cattle, it is possible to eradicate BLV even in farms where it is highly prevalent.
