A research project has determined that it probably isn’t a virus or bacteria (a biological agent) that links the Eastern tent caterpillar (ETC) to mare reproductive loss syndrome (MRLS). Bill Bernard, DVM, Dipl. ACVIM, an internal medicine specialist at Rood and Riddle Equine Hospital in Lexington, Ky., and Manu Sebastian, DVM, MS, a pathologist with the University of Kentucky’s Livestock Disease Diagnostic Center (LDDC), conducted the experiment in late May/early June. This project was funded by KTOB, creating what researchers are calling the “triad” approach–university, private practice, and industry involvement–to solving this problem.

The experiment showed that irradiated Eastern tent caterpillars can induce fetal loss in late-term pregnant mares. This suggests MRLS is caused by a non-infectious agent in caterpillars (irradiation at sufficient levels has been shown to kill infectious agents such as viruses and bacteria). The study was the first experiment to reproduce pathological findings similar to naturally occurring late-term MRLS