High incidences of leptospirosis-induced abortions in Central Kentucky mares could be caused by a tandem effect of temperature and precipitation in certain years, said Capt. David Hall of the U.S. Air Force, who defended his master’s thesis at the University of Kentucky’s (UK) Gluck Equine Research Center in Lexington on Dec. 15.

Leptospirosis is one of the most widespread zoonoses (diseases affecting both humans and animals) in the world. The bacteria cause flu-like symptoms in humans, and in horses can cause severe uveitis (moon blindness) and abortion. The disease is thought to be contracted through ingestion of contaminated soil or feedstuffs, or through cuts.

Hall’s project combined data from the UK Livestock Disease Diagnostic Center and The Jockey Club Thoroughbred breed registry from 1990-2004, plus survey data from 16 Central Kentucky Thoroughbred farms. Years with high levels of lepto-induced abortions were 1990, 1992, 1993, 2001, and 2004. Weather data from high-level abortion years showed temperatures remaining mild longer, then dropping off dramatically in early December rather than the gradual drop found in other years. Erratic precipitation was noted in weekly records of high-level years.

Age of the mare, parity (the number of live foals she delivered prior to a lepto-induced abortion), and her geographic location during gestation (relative to streams and watershed) weren’t significantly correlated with lepto-induced abortion. Mares that had a lepto-induced abortion had no difficulty with future pregnancies