Cross-sectional investigation of pathogenic Leptospira at the wildlife-livestock interface in a Cerrado-Atlantic Forest ecotone, Brazil.

Leptospirosis is a globally distributed zoonosis affecting domestic and wild species, particularly prevalent in regions with high temperature and humidity that favor leptospiral survival in the environment. This study investigated the role of wildlife-livestock interactions in the transmission cycle of Leptospira spp. Serum samples (for Microscopic Agglutination Test - MAT, considering dilutions ≥ 1:100 with ≥ 50% agglutination as reactive) and kidney tissues (for lipL32 PCR) were collected from 28 small mammals, including 14 marsupials and 14 rodents. All samples were seronegative by MAT; however, 15/28 (53.6%) kidney samples were PCR-positive, including 9/14 (64.3%) marsupials and 6/14 (42.9%) rodents. Additionally, 66 bovine serum samples from a dairy farm in the same area were analyzed by MAT, with 60/66 (90.9%) testing seropositive revealing high antibody titers (800), predominantly against serogroup Icterohaemorrhagiae (10%), followed by Sejroe (1.6%). Serogroup Pomona showed 1.6% of titers at 400. These findings suggest that small mammals might have played a significant role in the transmission and maintenance of pathogenic leptospires in the studied area, potentially acting as reservoirs and contributing to cattle infection. However, the observed infection patterns may also reflect indirect transmission routes, such as environmental persistence of leptospires in soil and water, or the involvement of additional, uninvestigated reservoir hosts within the agroecosystem. Therefore, small mammals sharing habitats with livestock should be considered important in leptospirosis epidemiology. Further studies evaluating leptospiral survival in environmental substrates, applying molecular typing to identify circulating strains, and conducting broader host surveillance are necessary to better elucidate transmission dynamics.