Bovine Leukemia Virus In Michigan Beef Bulls

Abstract

Bovine leukemia virus (BLV) is a contagious retrovirus of cattle. Little is known about the prevalence, risk factors, or potential health impact of BLV in beef cattle. Michigan beef bulls receiving breeding soundness examinations (BSE) were tested for BLV antibodies in serum using ELISA to determine the crude and age-specific prevalence of BLV in Michigan beef bulls. Our main objective was to measure the association between BSE results and BLV seropositivity. Additionally, management surveys were administered to the bull owners to identify potential risk factors for BLV infection. The crude BLV prevalence was 24.7% with an age-specific prevalence increasing with age from 1.5% to 67%. This indicates that these animals have a very low rate of BLV infection before they reach breeding age and then experience a very high rate of new infections once they begin natural breeding. Fertility, as measured by a BSE, did not appear to be affected by BLV infection. Scrotal circumference was the only measured BSE component that was associated with BLV infection. Exposure to cows through natural breeding and the frequency of changing hypodermic needles were the only management risk factors associated with BLV infection. The significant association between BLV infection and the reuse of hypodermic needles supports the findings of others in suggesting that needle reuse may be an important means of BLV transmission.