Leptospirosis prevalence and vaccination practices in South-West Victorian dairy herds

© 2019 Elke ErreggerWhile previous studies of Leptospira Hardjo in Victoria demonstrated a relatively high prevalence of exposure in both cattle (40%; Milner et al. 1980) and humans (22%; Sutherland 1988) these estimates need to be revised since they were made more than 30 years ago and leptospirosis vaccination programmes are now commonplace on Victorian dairy farms. This was a cross-sectional study to estimate the prevalence of Leptospira borgpetersenii sv Hardjo and Leptospira interrogans sv Pomona in dairy herds in South-Western Victoria. Fifty-three herds were enrolled into the study. Herd managers were asked to present 15 late-lactation cows that had fertility issues (cows that had not conceived or had delayed calving to conception intervals). Furosemide 500 mg was injected into the tail vein of eligible cows and a mid-stream urine sample of the second voiding collected to increase the likelihood of sampling leptospira .At the time of each herd visit a questionnaire was administered to herd managers asking them to provide details of methods used for controlling leptospirosis, including vaccination. Urine samples were pooled at the herd level and tested for leptospira spp. using qPCR. Pooled samples were then tested individually and samples that were positive, were tested for Leptospira Hardjo and Leptospira Pomona using qPCR. Three of the 53 pooled urine samples returned a positive result. The leptospira positive pools returned a minimum of three positive individual cow urine samples. Testing of individual cow urine samples identified an additional positive herd (with one weak positive and one inconclusive result), giving an apparent prevalence of approximately 8 (95% CI 1 to 13) leptospira-positive herds per 100 herds at risk. Based on the 53 completed questionnaires, leptospirosis vaccination programs were non-compliant with label directions in 35 out of 52 vaccinated herds: 67 (95% CI 54 to 78) out of 100 herds that routinely vaccinate for leptospirosis were doing so incorrectly. Of the 53 herds that took part in this study, only one herd was completely unvaccinated. Based on the findings from this study, and assuming the herds that took part in this study were an unbiased sample of the dairy herd population at risk, we estimate that close to one out of 10 dairy farms in South-Western Victoria are leptospirosis positive. While most herds are vaccinating for leptospirosis, most are doing so incorrectly. We conclude that herd managers need to be better educated regarding leptospirosis vaccination programs