Anne M. Eberhardt

Kentucky Reports MRLS Cases

Two fetal necropsy cases had findings consistent with the disease.

The University of Kentucky Livestock Disease Diagnostic Center reported today (May 13) that two fetal necropsy cases had findings consistent with mare reproductive loss syndrome, the disease that in 2001-2002 in Kentucky caused an estimated $336 in cumulative losses in all breeds of horses.

During 2001, when MRLS hit Central Kentucky particularly hard, an estimated 30% of the 2001-02 Thoroughbred foal crop was lost from late-term abortions and early-term fetal losses. Research at the University of Kentucky strongly linked Eastern tent caterpillars to the losses.

In the two recent cases, one was a late-term fetus, the other was an early fetal loss.

"We see a couple cases like this every year, and they are considered endemic, i.e. not a reason for major concern," said Dr. Craig Carter, director and professor of epidemiology at the LDDC. "This is the height of the Eastern tent caterpillar season. We strongly recommend that you refresh your clients' awareness on the importance of keeping  pregnant mares away from areas where the caterpillars are found."

For more information see the list of articles from on MRLS, and specifically the article Mare Reproductive Loss Syndrome Update.

The University of Kentucky indicated earlier this year that Eastern tent caterpillar populations were trending up. MRLS has previously been reported in several states, usually during the hatch and movement of caterpillars. Keep pregnant mares away from Eastern tent caterpillars (or other species) when the mares are at pasture, feed hay to minimize mares' consumption of caterpillars or their hairs while grazing, and use pesticides properly to kill caterpillars while they are in their nests.