Seroprevalence of Leptospira spp. in Horses in Israel.

This research investigates the prevalence of Leptospirosis, a bacterial disease, in horses in Israel, reporting the first identification of the Leptospira serogroup Pomona as the likely cause of Equine Recurrent Uveitis (ERU) in horses in the country and assessing the disease’s potential to transfer to humans.

Understanding Leptospirosis

• Leptospirosis is a bacterial disease that affects both humans and animals. It’s caused by the bacteria Leptospira.
• In horses, the disease can cause a condition called Equine Recurrent Uveitis (ERU), an inflammation of the uvea, a middle layer of the eye.
• Despite prior reports of Leptospirosis in humans and animals in Israel, no incidents involving horses had been documented until this research.

Investigation and Findings

• In the year 2018 in Israel, an outbreak of the Leptospira serogroup Pomona was recorded among humans and cattle. Subsequently, similar cases started emerging among horses, marking the first-reported instance of this serogroup as the likely cause of ERU in horses in the country.
• The researchers conducted an epidemiological investigation to study equine exposure across the region. They used a diagnostic process known as the microscopic agglutination test (MAT) to determine exposure to Leptospira, assisted by an investigation of eight different serovars (variants of a bacterial species).
• The results demonstrated that seven out of thirteen horses from a single farm tested positive for serogroup Pomona, with three experiencing signs of ERU.
• Further testing across three different farms during the same time period found 14 out of 70 horses to be positive for serogroup Pomona.

Historical Investigation and Implications

• A look into the past revealed that in 2015, two years before the outbreak, only one horse among the 259 sampled from 21 different farms tested positive for a different variant, serovar Icterohaemorrhagiae.
• By contrast, in 2018 (one year after the outbreak), 337 horses across 29 different farms were tested, and all samples came back negative for the bacteria.
• The research brings to light that horses, although not traditionally considered primary hosts of Leptospira, can indeed be infected and show symptoms during an outbreak in other species.
• The presence of leptospirosis in horses, particularly those in stable conditions, could pose a notable zoonotic risk—that is, a risk of diseases transferring from animals to humans. This is a concern that requires attention from both public health officials and owners given the close interaction between people and horses.