Predominance of Leptospira interrogans serovar Bratislava DNA in vaginal fluid of mares suggests sexual transmission of leptospirosis

• Presence of DNA of pathogenic Leptospira sp. in vaginal fluid of mares.
• First report of leptospiral DNA in equine vaginal fluid.
• Mares may become unapparent carriers.
• Potential for sexual transmission of leptospirosis in horses.

The purpose of the present study was to detect the presence of DNA of pathogenic Leptospira sp. in vaginal fluids of mares regarding a possible role of the sexual transmission. A total of 134 breeding mares from four troops were studied and sampling was conducted from vaginal fluids and urine for culture and PCR; and blood for serology. From the 134 serum samples tested, 59 (44%) were seroreactive, and serovar Bratislava was the most frequent (54.2%). None positive culture was obtained, but leptospiral DNA was detected by PCR (lipL32 gene) in 45 (33.5%) urine samples and 43 (32%) vaginal fluid (VF) samples. By phylogenetic analysis of the sequenced amplicons (secY gene) obtained after urine samples, it was found that 14/23 (60.9%) were of Bratislava and nine (39.1%) of Copenhageni. In contrast, the totality of the sequenced amplicons obtained after VF samples were of Bratislava serovar. This study demonstrated by the first time the presence of leptospiral DNA in the vaginal fluid of mares. Furthermore, the identification of that DNA as belonging to serovar Bratislava suggests that the transmission of leptospirosis in horses may occur by sexual via.