Consider Vaccinating Horses Against Botulism

The recent deaths of approximately 100 horses in Florida in an apparent outbreak of equine botulism have highlighted the need for a better understanding of the causes of the dreaded disease, and how it can be prevented.

Haylage contaminated with the botulinum toxin has been implicated as the culprit in the outbreak that spread quickly through a population of mares on a Florida embryo transfer farm (read more). Forage poisoning is the most common cause of the disease that, although well studied, fails to gain the attention of more publicized threats to horses.

"Historically, equine botulism has been considered a regional concern limited to areas of the country where Clostridium botulinum, the soilborne bacterium whose toxin causes the disease, is known to exist," said Dr. Jennifer Newman, Neogen's technical service veterinarian. "The traditional reach of C. botulinum type B has been in the temperate Mid-Atlantic soils of the United States, including Kentucky, Pennsylvania, and adjoining states. Types A and C are associated with the vicinities of Colorado, Utah, and the West Coast. Disease outbreaks occur so sporadically that people in non-endemic areas have let their guard down when it comes to the severity of botulism. However, as horses and feed are increasingly transported in and out of the endemic areas, this once regional concern is becoming more widespread.

"To address this increasing concern, the American Association of Equine Practitioners included botulism in the list of risk-based vaccines within its 2008 Vaccination Guidelines," she continued. "Horse owners routinely, and justifiably, have their animals vaccinated against tetanus, West Nile virus, Eastern and Western equine encephalomyelitis, rabies, and other diseases. Horse owners, with their veterinarians, should also be evaluating the risk posed to their animals by botulism and whether vaccination against botulism is beneficial."

Dr. Newman said Neogen, in cooperation with a number of veterinarians and veterinary hospitals, has launched educational programs to teach horse caregivers and owners how to preliminarily recognize and prevent the disease.

"Unfortunately, in Kentucky we have years of experience with equine botulism in the form of shaker foal syndrome," she said. "The disease can be very difficult to diagnose, because its clinical signs of reduced tongue tone, difficulty swallowing, muscle tremors, weakness, and recumbency mirror other diseases. The 'grain test' and 'tongue test' are two simple tests that veterinarians and horse owners can use initially when botulism is suspected. We have a great deal of additional clinical information available to the equine community on our Web site or by contacting Neogen directly."

Neogen provides the only USDA-approved vaccine against the predominant cause of equine botulism, C. botulinum Type B. First approved in 1987 and sold exclusively to veterinarians, BotVax B has safely and successfully protected hundreds of thousands of horses and foals from equine botulism and shaker foal syndrome.

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