Latest MRLS Study Points Directly to Caterpillars

A month-long study of the effects of Eastern Tent Caterpillars on pregnant mares points to the caterpillars themselves, not necessarily their waste, as the cause of early fetal loss associated with Mare Reproductive Loss Syndrome (MRLS).

A group of five mares was exposed to crushed starved Eastern Tent Caterpillars (ETC) mixed with water, a second group was exposed to their waste (frass) mixed with water, and a third control group received water. Four of the five mares in the group exposed to the ground up caterpillars lost their pregnancies within 13 days of exposure. None of the mares receiving frass or water aborted. All mares in the study were between 38 and 88 days into their pregnancies. Administration of the ETC, frass, and water was done by nasogastric tube for 10 days. Mares were housed in stalls with no exposure to grass 12 days before the study began and throughout the trial process.

Dr. Bill Bernard and Dr. Michelle LeBlanc of Rood and Riddle Equine Hospital and Dr. Bruce Webb of the University of Kentucky performed the study. The trials took place at Fasig-Tipton Sales Company near Lexington, which volunteered the stall space for the mares. Funding for the study came from the Grayson-Jockey Club Research Foundation, Fasig-Tipton, the Kentucky Thoroughbred Farm Managers' Club, Ernie Paragallo, Rood and Riddle, and Taylor Made Farm.

On June 3, 265 questionaires were mailed to Central Kentucky farms. Preliminary results from those surveys, returned from 92 farms, show an early fetal loss percentage below 8%. The farms who answered indicated that of their 2277 mares bred from Feb. 1-April 1, 2102 of those were in foal or 92.3% as of June 1.

The survey also asked respondents how their losses compared with 2001 and which of the risk management recommendations were followed by farm managers or owners. More detailed results are expected in coming weeks.