Acute leptospirosis in horses: A retrospective study of 11 cases (2015-2023).
Authors: Ramsay Lynette, Eberhardt Christina, Schoster Angelika
Journal: Journal of veterinary internal medicine
Summary
# Acute Leptospirosis in Horses: Clinical and Diagnostic Insights from 11 Cases (2015–2023) Leptospirosis remains an underrecognised disease in equine practice, with limited clinical data available to guide diagnosis and management. This retrospective case series examined 11 horses presenting with acute systemic leptospirosis over an eight-year period, identified through urine PCR, microscopic agglutination testing (MAT), or histopathology. Clinical presentations were remarkably consistent: lethargy and anorexia occurred in 10 cases each, whilst fever, tachypnoea and abnormal lung sounds were present in 9 cases, with epistaxis noted in 6 animals; critically, all 11 horses developed acute kidney injury, and approximately three-quarters (73%) showed evidence of pulmonary haemorrhage alongside hepatic involvement in 55% of cases. Urine quantitative PCR detected leptospiral DNA in just over half the cases (55%), whilst serological testing revealed that *Leptospira interrogans* serovars Australis, Autumnalis and Bratislava accounted for 86% of significant titres (≥1:800). The overall case fatality rate was 36% (4/11), with necropsy findings confirming tubular necrosis, interstitial nephritis, alveolar haemorrhage, and multi-organ involvement. Equine practitioners should maintain a high index of suspicion for leptospirosis in cases presenting with acute systemic inflammation, renal injury, epistaxis or unexplained hepatic disease—and paired testing using both MAT serology and urine PCR substantially increases diagnostic yield.
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Practical Takeaways
- •Include leptospirosis in your differential diagnosis for horses presenting with acute systemic inflammation, acute renal failure, epistaxis, or hepatic disease, even though cases are rare
- •Perform both urine PCR and MAT serology together to maximize detection; urine PCR alone was positive in only 55% of confirmed cases
- •Be aware that affected horses commonly show multi-organ involvement (kidney, lung, liver); expect high mortality risk with approximately 1 in 3 cases fatal
Key Findings
- •All 11 horses with acute leptospirosis presented with acute kidney injury; common signs included lethargy, anorexia, fever, tachypnea, and abnormal lung sounds
- •Pulmonary hemorrhage occurred in 73% of cases and liver disease in 55%; 55% had concurrent kidney, lung, and liver involvement
- •Leptospira interrogans serovars Australis, Autumnalis, and Bratislava accounted for 86% of serologic titers ≥1:800
- •Case fatality rate was 36% (4/11 horses); both urine PCR and MAT serology should be performed for optimal diagnosis