100 Horses Dead at Embryo Transfer Farm; Botulism Suspected

Around 100 horses have died at EquiTransfer, a Marion County, Fla., embryo transfer farm. Veterinary officials say that botulism from haylage might be to blame.

EquiTransfer is owned by veterinarians Jose Dávila, DVM, and his wife, Francis Ramirez, DVM. Neither were available for comment.

Mike Short, DVM, equine programs manager for Florida's Division of Animal Industry, said state officials are investigating, although they do not believe the deaths were caused by an infectious or contagious agent. Short said all signs point to botulism, including the history, clinical signs, type of feed (haylage is hay that has been fermented and packaged in airtight plastic), and death rate.

"I'll be surprised if it's not confirmed botulism," Short said. "So far the only horses that have gotten sick are the ones that ate that particular batch of haylage. All the horses that did not eat that are fine. We really believe it's toxin, and we have samples at several different universities."

Clinical signs included neurologic signs, tremors, difficulty breathing, recumbency, and sudden death, all of which, Short said, "are pretty typical of botulism."

Dávila has treated around 250 animals, including animals with clinical signs, with botulism antitoxin. The animals' positive response to the treatment is another indicator of the working diagnosis.

The haylage in question came from a single source, Short said. While the investigation is ongoing, they believe this supplier produces haylage for EquiTransfer exclusively--it doesn't appear that any other farms have received haylage from this source.

According to Kim Sprayberry, DVM, Dipl. ACVIM, in the article "Botulism: A Perfect Killer," botulism is an often-lethal disease caused by a bacterial toxin produced by Clostridium botulinum. It is particularly deadly in horses because they are more sensitive to the effects of the toxin than other animals.

"One problem occurs when rodents or other animals die in a field of forage and a carcass is incorporated into a bale during baling," Sprayberry wrote. "Because horses as a species are fastidious eaters, they will avoid consuming hay that is contaminated by animal remains when possible. However, when processed feeds such as cubes or pellets are fed, it is impossible for horses to eat around the contaminant, and consumption of the deadly spores can occur. Contaminated hay cubes have been responsible for at least one large outbreak of botulism in horses. Even if a carcass has undergone desiccation (it's dried out) or is unrecognizable in a flake of hay, enough spores can remain to kill a horse."

According to the EquiTransfer Web site, the company maintains more than 900 recipient mares on two properties. In 2006, the group performed more than 700 successful embryo transfers.

Adult horses and foals that recover from botulism appear to recover fully, with no residual nervous system deficits or muscle weakness. The botulism vaccine is an inactivated toxoid, which is extremely effective.

Short said test results might not be available for several days.

To learn more about botulism, see our Special Report.  

About the Author

Erin Ryder

Erin Ryder is a former news editor of The Horse: Your Guide To Equine Health Care. She owns a portly gray gelding named Duncan and dabbles in several equestrian disciplines, with an emphasis on dressage.

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