A Neglected Part of Bovine Genital Leptospirosis: Bulls

Bovine leptospirosis is a worldwide disease that causes reproductive issues, including early embryonic death, stillbirths and infertility, which result in significant economic losses. Although bovine leptospirosis is well-documented in cows, the role of bulls in harbouring and potentially transmitting genital leptospirosis has been largely neglected. We examined genital and blood samples from 16 slaughtered bulls using microscopic agglutination testing (MAT), polymerase chain reaction (PCR) and sequencing of amplicons. Our results showed that 81.2% of bulls were seroreactive, and 75% were genitally infected. The amplicons displayed an identity greater than 99% with Leptospira interrogans strains from the Sejroe serogroup, specifically serovar Hardjoprajitno. This study demonstrates that bulls can harbour in their genital tract the same leptospires associated with reproductive syndromes in cows from the same geographic region, highlighting the importance of bulls in maintaining and transmitting Sejroe serogroup strains associated with reproductive disease.