As with any infectious disease, any time that exposure can be minimized or eliminated helps to control an outbreak. Water sources and soil can be contaminated with Leptospira by urine from reservoir hosts such as wildlife, cattle, sheep, pigs and rodents. Keeping horses away from areas shared by these animals and away from stagnant water is an important preventive strategy. Periods of high rainfall increase the risk of exposure. In flood conditions, move horses to high, dry ground until stagnant and pooled water sources are diminished.
Following any case of abortion, the aborting mare should be isolated for 14-16 weeks and her urine tested periodically to ensure there is no further bacterial shedding. Abortive tissue that harbors Leptospira organisms can contaminate a large portion of ground around an abortion site. Common sense dictates keeping other horses out of the area and especially not feeding in that area. The contaminated ground should be cleaned and disinfected as best as possible to prevent wildlife exposure that would then maintain infection within that locale.
Recently, a USDA-licensed vaccine against Leptospira pomona has become available for use in pregnant mares: Lepto Eq Innovator (Zoetis). Studies indicate that 13% of bacterial abortions in mares are attributable to L. pomona. Nearly 95% of equine clinical leptospirosis cases affecting the reproductive tract and eyes are caused by L. pomona. Rare cases of L. grippotyphosa occur. Infected mares can shed the bacteria for up to three months, potentially transmitting infection to other horses. In studies leading up to USDA approval, vaccination with Lepto Eq Innovator entirely reduced urinary shedding from L. pomona. While Zoetis notes that no certainty exists for this vaccine to protect against abortion, equine recurrent uveitis or acute renal failure, it can reduce the potential risk.
Safety studies have demonstrated no systemic or local reactions when this vaccine was administered during all trimesters of pregnancy. Protocol recommends administering two vaccinations spaced 3-4 weeks apart, followed by an annual booster. The American Association of Equine Practitioners (AAEP) is recommending this vaccine as useful for broodmares at risk of exposure to leptospirosis.