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MRLS Update in Kentucky

© Patricia Celley

Here is the latest information I have found on the Mare Reproductive Loss Syndrome that hit Kentucky last month.

Researchers are still working on finding answers to this mystery. As of June 11, reports show occurrence of foal loss declining, but some mares are still losing foals. The last report from the Livestock Disease Diagnostic Center was on May 22 and reported 529 dead equine fetuses/foals submitted.

Cases of Pericarditis (fluid around the heart) continue to be significantly higher in horses of all breeds and ages in affected areas. Dr. Doug Byars, head of the internal medicine unit at Hagyard-Davidson-McGee (HDM) veterinary firm in Lexington, Ky., said veterinarians at his clinic and those at Rood and Riddle Equine Hospital are starting to see horses previously treated for pericarditis returning to the clinics with more heart problems. "This is looming as a problem that needs to be considered for the upcoming sales and beyond," Byars said. "It's a significant situation."

Byars recommends that horse owners and farm managers keep a close eye on horses. Watch for unexplained fever, lethargy, signs that indicate pneumonia, distention and pulsing of the jugular veins in the neck, and muffled heart sounds. Treatment may include draining fluid from around the heart.

A high number of unilateral eye problems have also been reported in the area. Researchers are studying the cause of these problems and their link to MRLS.

A survey of 150 farms went out on May 30, and most of them have been completed and returned. This survey provides 48,300 pieces of data that will be analyzed and entered into a database. You can view the survey at www.uky.edu/agriculture/vetscience/mrls/questionnaire.htm. When the results are thoroughly analyzed they will help identify risk factors and provide supportive information to the diagnostic team.

The leading hypotheses continues to be that the foals died from Cyanide poisoning. The Cyanide is believed to be produced by black cherry trees and transmitted by Eastern Tent Caterpillars after eating the leaves. The theory has been supported by tissue analysis of the foals/fetuses. It was also found that Eastern Tent Caterpillars sampled from May 4 showed no cyanide, while caterpillars collected from April 20 (right before the outbreak) showed very high levels.

But researchers are not excluding any possibility. A briefing from the University of Kentucky’s Veterinary Science on June 1, suggested hemlocks and the toxins associated with them may be a cause. They are also looking for other mycotoxins, fungal enophytes, phytoestrogens, chemical compounds and infectious agents. All tests prove the syndrome is not viral.

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