Acute leptospirosis in horses: A retrospective study of 11 cases (2015-2023).

The research article explores the signs, diagnostic methods, and clinical findings of leptospirosis in horses, based on the analysis of 11 cases. Through various diagnostic tests, the study discovered common symptoms and potential indicators of acute leptospirosis, identified the Leptospira strains most frequently involved, and highlighted the importance of using both serology and urine PCR tests for diagnosis.

Purpose and Methodology

• The research aimed to document and analyze clinical and diagnostic presentations of acute systemic leptospirosis in horses. The basis for this was the limited availability of studies evaluating this disease in horses.
• The researchers conducted a retrospective case study involving 11 client-owned horses, which were admitted to an equine hospital between 2015 and 2023 due to acute-onset illness.
• These horses were diagnosed with leptospirosis through one or more methods: urine PCR, serologic microscopic agglutination test (MAT), and histopathology.

Clinical Findings

• The most frequent symptoms of the disease included lethargy, anorexia, fever, tachypnea (rapid breathing), abnormal lung sounds, and epistaxis (nosebleed).
• All 11 horses exhibited acute kidney injury, signifying renal damage is a consistent feature of leptospirosis in horses.
• Pulmonary hemorrhage and liver disease were also prevalent, detected in 73% and 55% of the horses, respectively. More than half of the horses showed affliction in the kidneys, lungs, and liver simultaneously.

Diagnostic Findings

• The urine PCR test was successful in identifying pathogenic Leptospira spp, an organism responsible for leptospirosis, in 6 (55%) cases.
• The serology detected Leptospira interrogans serovar Australis, Autumnalis, and Bratislava as the most prevalent strains, responsible for 86% of all titers with a count greater than or equal to 1:800.

Case Fatality and Necropsy Findings

• The study observed a case fatality rate of 36%, with 4 out of 11 horses succumbing to the disease.
• Post-mortem examinations revealed tubular necrosis, interstitial nephritis (kidney inflammation), alveoli hemorrhage (lung bleeding), pulmonary edema (fluid in the lungs), periportal hepatitis (liver inflammation) and necrosis, cholestasis (bile flow disruption), and cholangitis (bile duct inflammation).

Conclusions

• The findings suggest that leptospirosis should be considered as a differential diagnosis for horses exhibiting acute systemic inflammation, acute kidney injury, epistaxis, or liver disease.
• The research indicates that both MAT serology and urine PCR should be performed for a higher likelihood of identifying positive leptospirosis cases.