The genital route in experimental infection with Leptospira spp. in hamsters as a model for genital leptospirosis.

Abstract

Leptospirosis is a globally distributed zoonosis that affects livestock reproduction. The causative Leptospira spp. are highly adaptable and can colonize a wide range of hosts. Although the intraperitoneal (IP) route is commonly used in experimental models, it bypasses mucosal barriers and does not reflect natural transmission. In contrast, mucosal routes, such as the intravaginal (IVG) route, more closely mimic natural infection but remain poorly investigated. This study evaluated the IVG route as an experimental model for reproductive leptospirosis using adult female golden Syrian hamsters (Mesocricetus auratus) inoculated with Leptospira santarosai serovar Guaricura via IVG or IP routes. To enhance susceptibility and standardization, IVG inoculations were performed exclusively during the proestrus or estrus stages, as determined by vaginal cytology. Animals were monitored for up to 40 days and assessed by serology and PCR. IVG-inoculated animals developed systemic infection and genital colonization, although bacteremia occurred later than in the IP group. Both groups elicited similar humoral immune responses from day 7 onward, with animals remaining seropositive until the end of the study. Renal and genital colonization was confirmed by PCR in both groups, with no significant differences. Importantly, 60 % of IVG-inoculated animals remained PCR-positive in genital tissues for up to 40 days, indicating persistent subclinical infection. No clinical signs were observed in any of the groups. The IVG route proved effective in establishing chronic infection and better simulates the natural course of animal genital leptospirosis, supporting its use as a physiologically relevant experimental model.