Abstract:
BACKGROUND : Reports of leptospirosis in horses are limited.
OBJECTIVES : To describe the clinical and diagnostic findings of acute systemic leptospirosis
in horses.
ANIMALS : Eleven client-owned horses presented to an equine hospital because of
acute onset of disease between 2015 and 2023.
METHODS : Retrospective case series. Horses diagnosed with leptospirosis by 1 or more
of urine PCR, serologic microscopic agglutination test (MAT), and histopathology.
RESULTS : Common clinical signs included lethargy (10), anorexia (10), fever (9), tachypnea
(9), abnormal lung sounds (9), and epistaxis (6). Acute kidney injury was present
in all cases. Evidence of pulmonary hemorrhage and liver disease was found in
8 (73%) and 6 (55%) horses, respectively. In 6 (55%) horses, kidneys, lungs, and liver
were affected. Urine quantitative polymerase chain reaction for detection of pathogenic
Leptospira spp. was positive in 6 (55%) cases. On serology Leptospira interrogans
serovar Australis, Autumnalis, and Bratislava accounted for 86% of all titers ≥1 : 800.
Overall case fatality rate was 4/11 (36%). Main findings on necropsy were tubular
necrosis, interstitial nephritis, hemorrhage in the alveoli, pulmonary edema, periportal
hepatitis and necrosis, cholestasis, and cholangitis.
CONCLUSIONS AND CLINICAL IMPORTANCE : Leptospirosis should be considered as a
differential diagnosis in horses with evidence of acute systemic inflammation and acute renal injury, epistaxis, or hepatic disease. For increased likelihood of identifying
positive cases, both MAT serology and urine PCR should be performed.
