July 12, 2001
Cherry Tree Leaves Said to Kill Foals
LEXINGTON, Ky. (AP) -- Scientists are convinced that cyanide naturally
present in cherry tree leaves was responsible for the mysterious illness
that killed hundreds of foals and fetuses in Kentucky thoroughbred country
Researchers still have not figured out exactly how the cyanide got into the
horses' systems. One theory is that Eastern tent caterpillars, which
infested the state in large numbers this spring, ate the leaves and
deposited the poison in grazing areas or drinking water.
To test that theory, researchers are feeding the leaves to the caterpillars
in the lab and studying the creatures and their excrement.
``I have no doubt that cyanide poisoning from cherry trees, or that combined
with some other natural toxin, was behind this syndrome. Hopefully, these
tests will be able to clear up some lingering questions,'' said Dr. Thomas
Tobin of the University of Kentucky's Gluck Equine Research Center.
``We've found that the caterpillars neutralize some of the poison before it
exits the body. But there's still plenty of poison there. Enough to affect
the horses if they eat excrement-laced grass or drink from a trough where a
number of caterpillars have drowned? That's what we're trying to
The mystery illness killed more than 500 foals and caused hundreds of mares
to spontaneously abort early in their pregnancies.
Scientists had theorized early on that fungus in pasture grass was
responsible, but tests for the toxins were negative.