Leptospirosis in horses in Ontario.

This research article analyses the prevalence of Leptospirosis, a zoonotic infection, amongst horses in Ontario. The study found that serovar bratislava, a subtype of the infection, is widespread but does not seem to play a significant role in horse abortions. The clinical relevancy of this infection in the local horse population still remains uncertain.

Overview of Leptospirosis and Its Serovars

• The research discusses leptospirosis, a bacterial disease and zoonotic infection, which affects many mammals, including horses. The disease is caused by spirochetes of the genus Leptospira.
• Leptospires, the bacteria causing the disease, exists in several strains or ‘serovars’. The research steers its focus towards seven serovars namely, autumnalis, bratislava, canicola, grippotyphosa, hardjo, icterohaemorrhagiae, pomona. Each serovar can have a varying degree of infection severity and prevalence in specific species or regions.

Seroprevalence of bratislava in Ontario horses

• The study found that serovar bratislava was significantly more prevalent in horses in southwest Ontario compared to the other serovars.
• Across the sample, seroprevalence (the level of a pathogen in a population, as measured in blood serum) of bratislava increased with age. Less young horses (5% of those aged two to three years old) showed antibodies to bratislava than older horses (52% of horses older than seven years).
• Similarly, a proportion of foals, or baby horses, showed antibodies to bratislava. Eight out of 16 foals from the study sample had developed antibodies to serovar bratislava between four and eight months of age.

Inconclusiveness of bratislava’s role in horse abortions

• Despite its high prevalence, the findings of the study do not support an important role for serovar bratislava in horse abortions. This is inferred from examinations of 52 aborted horse fetuses. Only one fetus showed evidence of a different serovar, kennewicki, instead.
• Additionally, examination of kidneys collected from 50 slaughtered horses turned out negative for leptospires, providing further evidence of the discrepancy in seroprevalence and clinical implication.

Unclear clinical significance

• While results show bratislava is widespread amongst horses in Ontario, the clinical significance is unclear. The specific symptoms or health issues the infected horses may suffer from, if any, are not indicated explicitly in this study.
• This forms the basis for future studies to explore how serovar bratislava affects horse health, and to compare results with those from other regions.