Letter to the Editor: Reflections on the reproductive syndrome in equine leptospirosis.

This research article discusses a study where horses were experimentally infected with a strain of Leptospira, an organism which can cause leptospirosis. Despite significant biochemical changes and antibody responses, the researchers could not fully establish the infection. The research expands knowledge on how Leptospira affects different livestock and highlights potential reproductive issues in horses linked to the Bratislava strain.

Background and Study

• The paper begins with a reference to an article written by Zilch and colleagues, reporting on a study of equine leptospirosis conducted by the Cornell University team. In this referenced study, a strain of Leptospirosis supposedly adapted to horses was used to experimentally infect horses.
• The study utilized a local strain of serovar Bratislava originally isolated from pigs. Despite observing significant biochemical changes and an increase in antibody titers, the researchers concluded that they were not successful in firmly establishing the infection in the horses.

Discussion: Leptospirosis and Reproductive Issues in Horses

• The editor’s team have been studying leptospirosis in horses for over two decades. They found the serovar Bratislava to be quite common in horses and noted it seems to cause a ‘silent’ disease, often manifesting as reproductive issues.
• In their recent research, the team has been focusing more specifically on the reproductive problems caused by Bratislava infection in horses. They discovered that the mares that were positive in urinary PCR and seroreactive for the Australis serogroup had significantly more reproductive problems than those reacting against Copenhageni.
• The reproductive problems were mainly early embryonic death, perinatal death, and abortion. The sequencing of leptospiral secY amplicons from cervicovaginal mucus samples showed only the presence of L interrogans serovar Bratislapi, reinforcing the hypothesis of this strain’s adaptation to the mare’s reproductive tract.

New Perspective on Leptospirosis

• The findings of Zilch’s team align with the editor’s team’s discoveries regarding the pathogenesis of Bratislava infection, particularly highlighting Leptospira’s access to the reproductive tract.
• The editor’s team also mentions infecting sheep with strains of the Sejroe serogroup in their past experiments, which resulted in a chronic and asymptomatic reproductive colonization similar to that reported by Zilch.
• Based on these observations, they have proposed a new terminology for this typical reproductive syndrome caused by leptospiral infection in livestock. In cattle, it has been named ‘bovine genital leptospirosis'(BGL).
• The overall findings and discussion question whether a similar silent infection syndrome exists in horses, showcasing the need to delve deeper into the leptospirologists’ studies to better understand this host-agent relationship in animal leptospirosis.