Texas Department of Agriculture Investigating Toxicity Deaths

The Texas Department of Agriculture is investigating the manner of pesticide application that led to the deaths of 27 horses at a boarding facility in College Station, Texas.


Veterinarians at Texas A&M University (TAMU) determined late last week that phosphine gas, a byproduct of aluminum phosphide fumigation tablets used to kill weevils in stored grain, was likely the cause of the horses' deaths.


Because of its extreme toxicity, aluminum phosphide is a regulated pesticide. Texas law requires that the chemical only be purchased and used by, or under the direct supervision of, a licensed pesticide applicator.


Farm owner Bradley Raphel told The Bryan-College Station Eagle, a local newspaper, that he applied the PhosFume pesticide late in the evening of July 15. He fed the horses the treated feed the next day.


The horses became ill shortly thereafter, with 24 dying within 12 hours. Three more died at TAMU's veterinary hospital later, where necropsies revealed phosphine gas in their stomach cavities.


Raphel told the Eagle that while he is not licensed to use the pesticide, he has done so on numerous previous occasions under the supervision of Walter Cronin, a personal friend who does have a license.


Cronin verified to the paper that he had overseen Raphel's treatment on prior occasions, but would not comment on whether he was present on July 15.


Guidelines from both the Texas Department of Agriculture and Douglas Products, the manufacturer of PhosFume, say that feed treated with phosphine must be aerated for 48 hours before being given to animals.


Sixteen horses that were in "guarded" condition are recovering at the farm. Another horse that was admitted to TAMU's veterinary hospital is recovering. The long-term effects of phosphine exposure in horses are unknown.


E. Murl Bailey, DVM, MS, PhD, Dipl. ABVT, a veterinary toxicologist at TAMU, says horses that survive phosphine exposure likely will develop liver and kidney problems.


"We don't know the exact mechanism of action of phosphine but we do know it inhibits the functioning of the cells in the body in such a way that energy production in the cells stops and the clinical signs exhibited by affected animals are a result of the lack of energy production," Bailey said. "The brain is very susceptible to a lack of energy production and this would cause the nervous signs which were seen in the affected horses in this case."


Sixteen of the deceased horses belonged to Raphel's family, including two breeding stallions, performance and lesson horses, as well as broodmares and foals. The Eagle reports that about 150 people attended a memorial service for the animals that was held Saturday night (July 22).


Read the Eagle's coverage here.

About the Author

Erin Ryder

Erin Ryder is a former news editor of The Horse: Your Guide To Equine Health Care.

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