06/10/2002 11:00PM

Caterpillars linked to foal deaths


LEXINGTON, Ky. - Ingesting crushed eastern tent caterpillars can cause mares to abort early fetuses, according to results of a new study.

In the study, headed by veterinarians Dr. Bill Bernard and Dr. Michelle LeBlanc and by University of Kentucky entomologist Dr. Bruce Webb, researchers dosed each of five pregnant mares with 50 grams of crushed caterpillars mixed in 50 milliliters of water. The researchers dosed the mares for 10 days using a tube that ran from a mare's nostrils into her stomach. The caterpillars were starved, meaning they did not contain cyanide-bearing wild cherry leaves, which can be toxic to horses.

Four of the five mares lost their pregnancies within eight to 13 days of their first dose. All of the mares were between 38 and 88 days of gestation at first dose, and the mares that aborted did so at 49, 64, 70, and 96 days of gestation.

Though the study covered a small sample of mares, the results appear to strengthen a theory that massive caterpillar infestation caused last year's wave of mare reproductive loss syndrome. MRLS caused thousands of early- and late-term abortions in central Kentucky broodmares. The study did not determine a specific toxin in the caterpillars that caused the abortions.

The study also dosed a second group of mares with 2.5 grams of caterpillar excrement mixed in 50 ml of water, and a third group of control mares, who received only 50 ml of water. None aborted. None showed signs of heart-swelling or eye problems, which also have been associated with MRLS.

All mares were kept off of grass starting 12 days before the first dose. Researchers maintained the mares in stalls throughout the experiment and walked them twice a day for exercise.