Seroprevalence of Leptospira in Lavradeiro horses, a semi-feral ecotype from the Northern Brazilian Amazon

Leptospirosis is a neglected zoonosis with significant impact on public and veterinary health, with equines acting as potential maintenance hosts of infection. This study aimed to investigate the seroprevalence of Leptospira in Lavradeiro horses under semi-feral conditions in Indigenous communities in the state of Roraima, Brazil. A total of 387 serum samples were subjected to the microscopic agglutination test (MAT), using antigens of Leptospira spp. from 18 serogroups. The overall prevalence was 15.8% (95% CI: 12.3-19.8%), with the most frequent serogroups being Australis, Tarassovi, Autumnalis, and Pomona. Seropositivity was higher among adult animals (17.6%) than foals (9.8%), although not statistically significant. Between sexes, there was no significant difference in positive females (16.8%) and males (14.7%). Horses that lived in areas that were likely to flood had a higher seroprevalence (23.6%). Titers of 800 or higher were found in 23 animals, most of which were from the municipality of Pacaraima. The Australis serogroup was the most common in this group. This study reports the first evidence of Leptospira exposure in Lavradeiro horses, with higher seroprevalence in flood-prone areas and reactivity to uncommon serovars. Our findings highlight pathogen circulation in equine under semi-feral conditions and the need for integrated surveillance and conservation of the Lavradeiro horse in the Northern Brazilian Amazon.