The U.S. Department of Agriculture has licensed an equine vaccine that protects against Leptospirosa pomona for use in broodmares during all three trimesters of pregnancy.

Leptospirosis, an infection of the L. pomona bacterium, can cause late-term abortion and recurrent uveitis in horses. The vaccine against leptospirosis, Lepto EQ Innovator, is manufactured and marketed by Zoetis.

Field safety studies, which examined the vaccine when used in the first, second, and third trimesters of pregnancy, showed no systemic or local reactions to vaccination.

A study showed that 13% of bacterial abortions are caused by L. pomona, the most common leptospiral serovar found in horses. Aborting mares have been reported to shed leptospires in their urine for periods up to three months and can transmit Leptospira to exposed animals. Some horses aborting due to leptospiral infection develop uveitis several weeks to months later. Additionally, the aborted fetus is a source of exposure to other horses on the property