Finding the hiding spots: uneven distribution of pathogenic Leptospira spp. in the bovine genital tract.

Background: Bovine genital leptospirosis (BGL) is a chronic reproductive disease caused by pathogenic Leptospira spp., whose uneven distribution in the genital tract may compromise diagnosis. Objective: This study evaluated the presence of pathogenic Leptospira spp. in different regions of the bovine reproductive tract of naturally infected cows to identify the most reliable anatomical site for molecular detection. Methods: Oviducts (OVID) and uterine fragments from the uterine body (UB), base of the uterine horn (BUH), and apex of the uterine horns (AUH) were collected post-mortem from 40 cows. Results: Pathogenic Leptospira spp. DNA was detected by lipL32 PCR in at least one anatomical site in 55% (22/40) of animals. The highest positivity rate was observed in UB (20/40; 50%), whereas AUH (7.5%), BUH (0%), and OVID (2.5%) showed no or minimal detection. Conclusion: The findings demonstrate that pathogenic Leptospira spp. are unevenly distributed within the bovine reproductive tract, with a clear preference for the uterine body. This anatomical site provides the greatest diagnostic accuracy and should be prioritized for molecular testing to minimize false-negative results and improve BGL surveillance.