Leptospirosis: An important infectious disease in North American horses.
Authors: Divers T J, Chang Y-F, Irby N L, Smith J L, Carter C N
Journal: Equine veterinary journal
Summary
Leptospira Pomona type kennewicki, rather than the more commonly detected Leptospira Bratislava, is the primary pathogenic serovar affecting North American horses, causing reproductive failure in mares, acute renal disease in younger animals, and recurrent uveitis in adults. Whilst the research team reviewed existing evidence across multiple clinical syndromes, they emphasise that diagnostic protocols combining antigen and antibody detection methods are essential, particularly given that infected mares may shed organisms in urine for weeks post-abortion without displaying obvious clinical signs. Acute renal failure responds well to antimicrobial therapy with supportive care, yet antibiotic efficacy for reducing leptospiral shedding and preventing abortion remains poorly documented, and systemic antimicrobials have proven ineffective for Leptospira-associated uveitis despite chronic intraocular infection. The recent availability of an equine-approved Leptospira Pomona kennewicki vaccine offers a significant advance in prevention strategies, though practitioners should remain vigilant about diagnostic testing in pregnant mares and young horses presenting with renal dysfunction or recurrent eye disease. For stud farms and breeding operations particularly, understanding the asymptomatic shedding risk and lack of proven prophylactic protocols underscores the value of vaccination and careful management of potentially exposed animals.
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Practical Takeaways
- •Screen and vaccinate breeding mares against Leptospira Pomona type kennewicki to prevent abortion and neonatal disease; infected mares may shed organisms in urine for weeks post-abortion without other clinical signs.
- •Recognize recurrent uveitis in adult horses as a potential sequela of prior leptospiral infection months or years earlier; systemic antibiotics are ineffective for ocular disease despite intraocular infection.
- •Treat acute renal failure from leptospirosis aggressively with antibiotics and supportive care, as this syndrome responds well to intervention in younger horses.
Key Findings
- •Leptospira Pomona type kennewicki is the primary cause of clinical leptospirosis in North American horses, while Leptospira Bratislava is most commonly exposed but has not been confirmed to cause clinical disease.
- •Leptospirosis manifests as three distinct clinical syndromes: abortion and neonatal disease in pregnant mares, acute renal failure in younger horses, and recurrent uveitis in adult horses often developing months or years post-infection.
- •Antibiotic efficacy for leptospirosis treatment is inconsistent; systemic antimicrobial therapy has not been effective for ocular leptospirosis despite chronic intraocular infection, though antibiotics with supportive care can successfully treat acute renal failure.
- •An equine-approved Leptospira Pomona type kennewicki vaccine is now available in North America for prevention.