Vaccination practices for Leptospira spp. on New Zealand dairy farms
To describe leptospiral vaccination practices in dairy herds in New Zealand and evaluate conformity with best practice guidelines issued by the New Zealand Veterinary Association using data from a questionnaire administered by participating veterinary practices.
A cross-sectional study of 200 randomly selected dairy farms stratified by herd size and region throughout New Zealand was conducted from January to April 2016 to investigate leptospiral vaccination practices in dairy herds in New Zealand. Using a pre-tested questionnaire administered during a face-to-face interview, vaccination practice details such as vaccine types, time, and age of vaccination and whether vaccines were administered by veterinary or farm staff, were collected.
Leptospiral vaccination programmes had been implemented on 199/200 (99.5 (95% CI = 97.2–99.9)%) farms, and on 178 (89.4%) of those, programmes had been running for ≥5 years. Most farmers used bivalent vaccines containing antigens for leptospiral serovars Pomona and Hardjo (144/179 (80.4%) in calves, 112/167 (60.7%) in heifers, and 112/163 (68.7%) in cows), rather than trivalent vaccines which also include antigens for L. interrogans serovar Copenhageni. In total, 123/200 (61.5%) of farmers purchased only vaccinated animals but 51/199 (25.6%) were unsure of the vaccination status of purchased cattle. Sixty-one percent (105/172) of farmers had other livestock on their farms and of them, 78/186 (42%) vaccinated some or all for Leptospira spp. Leptospiral vaccines were administered always or sometimes with other animal remedies on 30/190 (15.8%) and 91/190 (47.9%) of farms, respectively. Most farmers had not made changes to their vaccination programme in the previous 5 years. Timing of first vaccination of calves ranged from 2 weeks to 10 months of age, with 112/189 (59.3%) vaccinating by 4 months of age. Approximately half of the farms followed the best practice guideline for the timing of vaccinations for calves (high-risk farms; 67/162; 41.4%) heifers (72/165, 43.6%), and cows (171/184; 92.9%).
The results of this survey suggest that there is almost universal adoption of leptospiral vaccination for dairy cattle in New Zealand. However, there remain areas for improvement regarding the proportion of farmers following best practice guidelines and refinement of vaccination programmes, particularly with respect to timing of vaccination in calves.