Mare Reproductive Loss Syndrome (MRLS) Confirmed in Florida

On Wednesday, March 29, the University of Florida (UF) College of Veterinary Medicine confirmed one case of MRLS and has two other cases that are suspect. All three cases occurred in Alachua County, Florida this spring.

Two cases were septic foals that received treatment in the UFCVM intensive care unit but were subsequently euthanized. The third case was a late-term abortion.

Diagnosis of MRLS was confirmed by UF pathologist Dr. John Roberts who worked at the University of Kentucky Livestock Disease Diagnostic Center during the Kentucky MRLS outbreak of 2001-2002.

MRLS has not been previously reported in Florida. The Kentucky outbreak suffered severe economic losses estimated to be near $336-500 million and a loss of 30 percent of the estimated foal crop for 2002.

MRLS has been linked to the consumption of Eastern Tent caterpillars. Eastern tent caterpillars prefer wild cherry, apple and crabapple. The clinical syndromes include early pregnancy loss, late-term abortions, foals born weak and septic, pericarditis, uveitis, laminits and oral ulceration.

Mare Owners: Take Action

At this time, we strongly recommend that all abortions and foal deaths receive a post-mortem evaluation. Inspection of pastures for the presence of cherry trees and caterpillars is critical. The only way to protect the pregnant mare is to remove her from contact with the caterpillars. Early pregnancy loss can be detected by ultrasonographic evaluation.

For more information, consult the University of Kentucky web page on MRLS at or The Horse: Your Guide to Equine Health Care at

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