North Carolina Horse Toxicity Investigation Continues

Veterinarians are still searching for what caused the deaths of four horses in Fairview, N.C., earlier this month.

An analysis of the animals' feed failed to reveal the presence of a specific ionophore (antimicrobial compound) called monensin, which investigators believed could have poisoned the horses. Monensin is an additive found in cattle feed that is toxic to equines.

Despite not finding ionophores in the feed samples, Richard Oliver, DVM, of the Western North Carolina Diagnostic Laboratory, said those working on the case still are "speculating it's an ionophore," because these compounds can be found naturally in the environment as well.

Frozen muscle tissues have been sent to a lab at the University of Minnesota for analysis.

The afflicted horses showed signs of lethargy, muscle stiffness, dark urine, sweating, and shaking. No other horses in the area have shown similar clinical signs since the last died a week ago.

Area veterinarians continue to recommend that horse owners keep their animals off pastures.

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Liz Brown

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