Seroprevalence of equine leptospirosis in Connecticut, US.

Authors

Camila Hamond, Candace L Kangas, Vivianne W Lee, Anayah Fanfan, Jarlath E Nally, Holly McGinnis, Maureen Sims, Guillermo R Risatti, Elsio Augusto Wunder

Published in

BMC veterinary research. Volume 22. Issue 1. Aug 01, 2026. Epub Aug 01, 2026.

Abstract

Leptospirosis is a geographically widespread neglected zoonotic disease caused by pathogenic spirochetes of the Leptospira genus. Horses can act as subclinical reservoir hosts, which are characterized as asymptomatic carriers that persistently excrete leptospires through their urine and transmit the disease. Horses play an important role in the lives of Connecticut (CT) residents in the form of leisure pursuits and related business activities. Nevertheless, there is a limited understanding of horse exposure to Leptospira in CT. This investigation sought to determine the prevalence of anti-Leptospira antibodies in horses in Connecticut, US. A total of 397 sera were tested by the microscopic agglutination test (MAT). The antigen panel included 40 strains representing 26 serogroups and four autochthonous isolates (not determined serogroup).
The overall horse seropositivity (established as a titer ≥ 1:100) was 61.5% (244/397). The most detected serogroups were Djasiman, Grippotyphosa, Australis, Pomona, Icterohaemorrhagiae, and serovar Room22 strain GWTS1. Cross reaction for more than one serogroup was found in 80/244 (32.8%). As a limitation, the MAT does not differentiate between natural exposure and vaccination. However, Leptospira bacterin for horses includes only serogroup Pomona in the U.S. Therefore, after eliminating Pomona results to reduce potential vaccination bias, the seroprevalence was 204/397 (51.4%).
Our results showed a high seroprevalence of leptospirosis in Connecticut and strong evidence that animals were potentially exposed to serogroups/serovars not included in commercial bacterins. Further studies to attempt isolation and genotyping of the pathogen from horses are necessary to better understand the role of horses in the epidemiology of leptospirosis. This information will support diagnostic strategies, vaccine recommendations, risk assessment, and public health actions that can reduce spillover transmission and the impact of this important zoonotic disease.

PMID:
42958252
Bibliographic data and abstract were imported from PubMed on 30 Oct 2026.

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