Toxin Suspected in North Carolina Horse Deaths

Veterinarians are trying to determine the cause of an illness that has killed four horses in Fairview, N.C., since last Thursday.

Affected horses show a rapid deterioration in muscle condition. Other clinical signs include lethargy, shaking, dark urine, sweating, and stiff muscles. The last horse died on Monday. The four horses lived on two separate farms, across a creek from each other.

Richard Oliver, DVM, of the Western North Carolina Diagnostic Laboratory, who has been working on the case, suspects the illness is caused by a toxin. There are two sources he thinks are most likely, although more tests are needed to determine if his suspicions are correct.

One is that the poisoning could be caused by ionophores, antimicrobial compounds that are used in cattle feed and that also occur naturally. The other theory is that the horses might have consumed a toxic plant. Oliver said hairy vetch, coffee senna, and white snakeroot are the most likely suspects.

"We won't know where we stand until we analyze feed and tissue samples, and stomach contents," said Oliver.

For now, practicing veterinarians in the area advise horse owners to keep their animals off pasture to avoid possible exposure to the toxin.

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Liz Brown

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