Single-use hypodermic needles and obstetric sleeves failed to reduce bovine leukemia virus transmission in three dairy herds

The objective of this study was to determine the utility of single-use hypodermic needles and reproductive examination sleeves in reducing the transmission of bovine leukemia virus (BLV) in dairy herds. Numerous epidemiological studies have identified re-use of needles and exam sleeves as significant risk factors for BLV, therefore adopting a practice of single-use needles and sleeves is a commonly suggested management change for reducing BLV transmission. We conducted a field trial on 3 midwestern commercial dairy herds that had not been employing single use of needles or sleeves as part of their herd health protocol. Additionally, each of the herds had a BLV prevalence among adult cows of at least 20%. BLV milk-ELISA negative cows were randomly assigned to always receive a new single-use needle and new exam sleeve (intervention group). We also monitored and tested BLV milk-ELISA negative cows that received the standard management practice of needles and sleeves that were shared with ELISA-positive herd mates (controls). Cumulative incidence of new infections was determined by semiannual BLV milk-ELISA testing. The cumulative incidence of new BLV infections was not statistically different between the 2 groups. Medical hygiene to prevent bloodborne transmission is still recommended, but in these 3 herds, re-use of needles and sleeves did not appear to be a major route of BLV transmission.