A Study on Preventing Enzootic Bovine Leukosis Using Nested-PCR for Identification of Infected Calves on a Dairy Farm

Abstract

To prevent bovine leukemia virus (BLV) infection among cattle on a dairy farm, we identified calves that were infected with BLV using nested-PCR from May 2015 to December 2016. Twenty-five calves born from BLV-infected cows were examined during the birth month and the following month. Among these, 2 calves were identified as being infected with BLV. All calves under 6 months of age were examined 3 times for periodic surveillance of BLV infection, and 2 of 35 calves were identified as being infected. The 4 calves infected with BLV, with ages ranging from 19 days to 5 months, were culled from the farm. We implemented precautionary measures to avoid horizontal transmission of BLV in the herd of growing cattle on the dairy farm from May 2015. We evaluated the rate of conversion from seronegative to seropositive in the herd from June 2014 to May 2015 and from May 2015 to April 2016. The rate of conversion decreased from 64.7% to 12.5% (P＜0.05). The seroprevalence rate in the herd decreased to 0% in December 2015. Our study results indicate that identification of BLV-infected calves using nested-PCR can be a useful approach to prevent BLV infection on dairy farms and reduce breeding costs for growing calves.