Molecular detection of pathogenic Leptospira spp. in mares with reproductive disorders enrolled in embryo transfer...

Equine genital leptospirosis (EGL) is associated with reproductive disorders in mares. However, its occurrence in embryo transfer (ET) programs remains poorly characterized.

Given the scarcity of data on the circulation of Leptospira spp. in mares enrolled in ET programs, this study aimed to investigate the serological and molecular occurrence of Leptospira spp. in mares with a history of reproductive disorders from 13 stud farms dedicated to embryo transfer in Brazil.

Serum and endometrial cytobrush samples (ECS) were collected from 70 unvaccinated mares. Serological analysis was performed using the microscopic agglutination test (MAT), and molecular detection was conducted by PCR targeting the lipL32 gene. Positive samples were subjected to sequencing.

In the MAT, 68.6% (48/70; 95% CI: 56.9-78.2) of mares were reactive at titers ≥ 1:100. PCR detected pathogenic Leptospira DNA in 45.7% (32/70; 95% CI: 34.5-57.4) of ECS, with at least one positive mare identified in 92.3% (12/13) of farms. Sequencing of one sample showed ≥ 99% nucleotide identity with Leptospira interrogans. Functional classification was significantly associated with PCR positivity, with recipient mares presenting higher odds of detection compared to donors (OR = 3.15; 95% CI: 1.05-9.43; p = 0.040).

These findings demonstrate high serological exposure and molecular evidence of infection in the reproductive tract of mares with reproductive disorders, reinforcing the importance of molecular investigation in breeding herds enrolled in ET programs.