Authors: Bolwell Charlotte F, Rogers Chris W, Benschop Jackie, Collins-Emerson Julie M, Adams Brooke, Scarfe Katherine R, Gee Erica K
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Leptospira Seroprevalence in New Zealand Thoroughbreds A quarter of Thoroughbred horses surveyed across 25 North Island properties in New Zealand showed serological evidence of Leptospira exposure, with 124 of 499 animals testing positive (25%, 95% CI 21–29%) to at least one of five serovars—Ballum, Copenhageni, Hardjo (bovis), Pomona, and Tarassovi each affecting 5–9% of the cohort individually. This cross-sectional study combined serological testing via microscopic agglutination with detailed questionnaires on grazing practices, pest management, waterway access, and wildlife contact to identify exposure routes through logistic regression analysis. Broodmares carried significantly higher odds of infection than racehorses, whilst concurrent grazing with sheep or cattle proved pivotal to serovar-specific risk: sheep grazing increased Ballum and Hardjo (bovis) exposure, and alternate cattle grazing elevated Hardjo (bovis) specifically. The findings reinforce that leptospiral exposure in pastured horses occurs primarily through environmental contamination rather than direct animal contact, implicating rodent reservoirs and shared grazing management as key epidemiological factors. For practitioners, this suggests that breeding operations and properties with mixed livestock warrant enhanced biosecurity protocols, rodent control measures, and consideration of waterway contamination risk when investigating reproductive losses, renal disease, or uveitis in affected herds.
Read the full abstract on PubMed
Practical Takeaways
- •Leptospira exposure is common in New Zealand Thoroughbreds (1 in 4 horses), particularly in breeding operations—test breeding stock and manage pasture contacts accordingly
- •Management practices matter: minimize co-grazing with other livestock and implement rodent control to reduce pasture-based transmission risk
- •Broodmares warrant particular attention for Leptospira surveillance given their elevated exposure risk compared to racing stock
Key Findings
- •25% (124/499) of Thoroughbred horses had positive antibody titres to at least one Leptospira serovar
- •Individual serovar seroprevalence ranged from 5-9%, with Copenhageni being most prevalent at 9%
- •Broodmares had significantly higher odds of exposure to any serovar compared to racehorses
- •Co-grazing with sheep and cattle increased odds of exposure to specific serovars (Ballum and Hardjo bovis respectively)