What I’ve learned about the dangers of the caterpillar and the pregnant mare:
Even though I did have a necropsy performed on Isabella’s baby, the results were inconclusive; other than a red bag. The UF vets warned me that if it was the caterpillar, that that would be the case. The only way they finally figured it out in Kentucky back in 2001 (when they had $500 million in losses) was to feed pregnant mares the caterpillars, causing most of the mares to abort. The barbed hairs on the caterpillar are almost impossible to find once they’ve passed through the mare. So, after much discussion with the vets at UF, they said that the caterpillar was most likely the culprit of both my late term abortions. In my case it was easier to diagnose because, the 2 mares that were able to deliver foals on my farm (Galana and a Lusitano mare) both spent the first 9 months of their pregnancy off my farm; not exposed to the caterpillar. The 2 mares that lost their foals (Isabella and Sugar) were here throughout their pregnancy.
What I plan to do for this next Spring foal crop: All of the mares will be coming in starting late December; they are out full time right now. I have a paddock that is not bordered by any trees and has only 2 trees in it - this will be my control paddock. I will begin treating this paddock with BT (Bacillus thuringiensis) in early December. (The caterpillar season for us is January-March.) The pregnant mares will be able to be turned out a few hours a day, in this control paddock, for those months when the caterpillar is active. This is about the best I can do and I feel more confident now that I have a plan.
Also - it is important to note that ALL of the caterpillars you find with those little hairs all over, are dangerous to your horses, and most especially your pregnant mares. I know that Colorado has the Forest Tent Caterpillar and the Western Tent Caterpillar, but their may be others.
