Experiment Links Caterpillars With Reproductive Loss

Eastern tent caterpillars, plus bacteria and a means to infect placental fluids with the bacteria, equals mare reproductive loss syndrome. It might be as simple as that.

In an experiment in which the caterpillars were fed to pigs, researchers found microscopic sores (microgranulomas--much like when you get a splinter in your finger) throughout the alimentary tract (from the mouth to the large colon). There were hundreds of thousands, if not millions, of the tiny sores in each pig. And in the middle of the sores was a piece of setae, which are the hair-like projections on the outside of caterpillars.

It's possible the microgranulomas could offer an entry portal into the circulatory system for the bacteria normally found in the horse's digestive tract. So, wherever the circulatory system carries these bacteria, they could cause problems--for example in the reproductive system, eye, heart, and brain.

Early in the foal loss syndrome in 2001, researchers at the Kentucky Livestock Disease Diagnostic Center noticed an unusual abundance of a couple of families of bacteria in aborted fetuses (Streptococcus and Actinobacillus). The bacteria are normally found throughout the alimentary tract of horses.

Dr. Bruce Webb, an entomologist at the University of Kentucky's Department of Agriculture, has been behind many of the caterpillar experiments. "This is a great story of biologic interactions," Webb said. "You might not recognize certain data is important, but eventually it will fall into place, like the bacteria/Eastern tent caterpillar relationship."

"We don't know if this is leading to abortions, or if the reaction is just there because the pigs were consuming caterpillars," said Dr. Neil Williams of the University of Kentucky's Livestock Disease Diagnostic Center. "There are plans in the immediate future to look for these types of lesions in the mare."

Results should be known soon of research to find out if horses get the microgranuloma sores in the alimentary tract.