The Picture of MRLS in One Month...

The Grayson-Jockey Club Research Foundation is funding a collaborative look at caterpillars, their frass (excrement), and early fetal loss associated with mare reproductive loss syndrome (MRLS). It is possible that after this experiment--which begins on May 20 and will take 31 days--that researchers and managers will have a positive indicator that caterpillars and/or their frass are associated with MRLS, and if mares show symptoms prior to loss. It is hoped that the study will also suggest how to manage mares to protect them and their fetuses, or if there is something else involved in the early fetal losses.

Leading the research project is Dr. Bill Bernard, an internal medicine specialist with the Rood and Riddle Equine Hospital in Lexington, Ky., and president of the Kentucky Association of Equine Practitioners. Others involved in the research are Dr. Bruce Webb, an entomologist at the University of Kentucky who conducted the first caterpillar/frass/MRLS trail this spring; Dr. Michelle LeBlanc, a reproduction specialist with Rood and Riddle; and other local private practitioners.

A group of 17 pregnant mares between 40-80 days gestation will be stalled and observed for at least seven days prior to the start of the study. They will be hand-walked for exercise, fed a grain concentrate and free-choice grass hay, but allowed no grazing time. If all mares are reproductively normal after the minimum seven days, 15 will be chosen for the research (excluded will be one which is the least number of days pregnant and one which is the most number of days pregnant).

The mares will have ophthalmologic (eye) and cardiology (heart) exams to ensure normalcy before being randomly assigned to one of three groups. One group will be given stored caterpillar frass from Webb’s lab; one group will be given caterpillars that haven’t been fed and have no frass; and one will be given only saline as a control. All mares will be dosed using a nasogastric tube (like was used in years past for deworming).

The mares will be monitored three times a day for body temperature and physical soundness, with blood drawn daily for examination and storage for future study. The mares will receive a reproductive ultrasound once daily during the treatment and continuing on for 11 more days (a total of three weeks). Cardiac and ophthalmologic exams will be conducted once weekly for those three weeks unless some abnormality is suspected. Cultures from mares and fetuses will be collected in the case of abortion.

This research should determine if early fetal loss in MRLS is due to ingestion of frass and/or caterpillars.

Researchers hope that mares will show some clinical signs before they abort, thus giving clinicians a chance to develop management techniques to save the pregnancy. This research also will let managers know if there is an association between pastures and early fetal loss, or if it is strictly due to caterpillars and/or frass. Also, samples collected from this study might help determine the causative agent and how it affects the mares’ pregnancies, thus allowing for future preventive management.

About the Author

Kimberly S. Brown

Kimberly S. Brown was the Publisher/Editor of The Horse: Your Guide To Equine Health Care from June 2008 to March 2010, and she served in various positions at Blood-Horse Publications since 1980.

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