Combination of Factors Contribute to Leptospirosis-Induced Abortions

High incidences of leptospirosis-induced abortions in Central Kentucky horses 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 Masters thesis on the subject at the University of Kentucky's Gluck Equine Research Center in Lexington, Ky. Dec. 15.

Leptospirosis is one of the most widespread zoonoses 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 and abrasions.

Hall's project combined retrospective data from the University of Kentucky 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 the weekly records of high-level years.

Age of the mare, parity (the number of live foals prior to a leptospiral-induced abortion), and geographic location of the mare during gestation (relative to streams and areas of watershed) were not significantly correlated with leptospirosis-induced abortion. Mares that had a leptospirosis-induced abortion did not appear to have difficulty with future pregnancies.

Hall suggested skunks could be a reservoir for the incriminated leptospira serovar in Central Kentucky, although further research is needed to determine the environmental sources. Scientists attending Hall's talk suggested that other wildlife, including rodents, could be possible carriers.