In Hollywood, botulism is a cosmetic quick-fix used to reduce lines and wrinkles and provide a youthful glow. But in the horse barn, botulism is much scarier than aging skin. Itâs a disease that can be very deadly and expensive to treat.
Preventing botulism in horses
Botulism is a progressive neuromuscular disease that quickly leads to weakness and flaccid paralysis or the lack of muscle tone with the reduced ability to move and typically leads to death of the horse if itâs not treated soon after the onset of clinical signs.
In addition, there are many misconceptions: itâs only a problem in Kentucky, it can only be found in round bales, and if a horse acquires botulism, human negligence must be involved. All of these presumptions are false.
The Neogen Corporation, based in Lansing, Mich., and Lexington, Ky., has started a campaign to help educate horse owners across the country about this potentially deadly disease. The company wants to educate the equine community by explaining that botulism isnât always a disease of negligence.
Itâs considered to be a silent killer, because it can often cause the death of an animal with no warning at all. When horse owners are afraid to share their stories, it makes research and education about the disease much more difficult.
What is Botulism?
Botulism is a progressive neuromuscular disease that quickly leads to weakness and flaccid paralysis or the lack of muscle tone with the reduced ability to move. It can be severe and typically leads to death if itâs not treated soon after the onset of clinical signs. The disease is caused by toxins that have been produced by an anaerobic, spore-forming, soil-dwelling bacterium called Clostidium botulinum. There are three types (A, B, and C) that can affect horses, but 85 percent of the cases in North America are type B.
âThe toxin can affect all mammals, but the horse is super, super sensitive,â explains Bonnie Barr, VMD, Dipl. ACVIM, of Rood & Riddle Equine Hospital in Lexington, Ky. âPretty much, the amount of toxin that can be on the tip of a pencil can make a horse recumbent, unable get up, and eventually die.â
There are three different ways a horse can contract botulism. The first, and probably most common, is via forage poisoning. Intoxication occurs when a horse ingests preformed toxin from contaminated feed.
Preformed toxin can be found in any feed, but it is most commonly found in improperly made or stored forages (e.g., round or square hay bales, hay cubes, etc.) or in food contaminated with animal carcasses containing C. botulinum. If C. botulinum establishes infection in a wound (such as umbilical infections, castration sites, puncture wounds, and injection site abscesses), wound botulism occurs.
Finally, younger horses can contract botulism. Soil-borne C. botulinum spores are ingested by the foal, and they infect the gastrointestinal tract. Toxicoinfectious botulism, or shaker foal syndrome, can affect foals from a few days old to several months of age.
Deciphering the Clinical Signs
Clinical signs resulting from botulism poisoning can resemble those of a horse suffering from a severe bout of colic. If the horse isnât treated quickly, the situation can go downhill rather quickly. Typically, clinical signs of botulism are observed within 24 hours of exposure to the toxin, or as little as 12 hours.
âThe most common sign is an overall weakness,â points out Dr. Barr. âA horse with botulism will be dysphasic and unable to swallow. If you pull a horseâs tongue out the side of his mouth, a normal horse will be able to pull it right back in, but a horse with botulism canât. They canât get their tongue back in their mouth. Youâll see a loss in eyelid tone.
With a normal horse, if you go up to him and try to pull up his eyelid, his eyelid tone is going to make it difficult for you to do that. But, itâs easy to do with a horse with botulism. Itâs the same with tail tone. Try to grab your horseâs tail and lift it up. Youâll feel some resistance, but, in a horse with botulism, you wonât.â
Other signs include eating more slowly, foals leaking milk from the mouth while suckling, recumbency or inability to rise, and even colic. What makes it difficult for horse owners to diagnose botulism is how this disease mimics the primary clinical signs of other diseases such as tetanus, equine protozoal myeloencephalitis (EPM), equine herpesvirus-1 (EHV-1), Eastern equine encephalomyelitis (EEE), and West Nile virus (WNV). How can you tell the difference?
âHorses with EPM are weak,â explains Dr. Barr. âA lot of times, those horsesâ coordination is abnormal. A lot of times, theyâll have muscle atrophy, and botulism-affected horses donât have that.â
For horses with EHV-1, they usually have a history of fever prior to their onset of neurologic signs. Also, horses with the neurologic form of EHV-1 will be affected more in their hind limbs rather than their front limbs, whereas botulism is a generalized muscle weakness.
Veterinarians can conduct simple tests to help diagnose botulism, including pulling on the tongue.The other is called the âgrain testâ in which a small amount of sweet feed is offered in a large flat tub and a vet monitors how long it takes the horse to eat the feed.
If botulism is recognized early, there is a chance to save the horse using an antitoxin and supportive therapy. An affected horse might require several days of round-the-clock intensive care at an equine hospital. Hospitalization can be very costlyâ with just $1,000+ for the antitoxin alone, and this doesnât include intensive hospitalization and rehabilitation.
The Best Defense is Prevention
There is no comparison between the cost of treatment and the cost of vaccination. Botulism can be prevented with the use of one vaccine, which is the only USDA-approved vaccine for Clostridium botulinum type B, called BotVax B, made by Neogen. An initial vaccination includes three separate doses in one month intervals.
After that, horses can be vaccinated once a year. Even if your region is not known to have a problem with botulism, you might be traveling to another part of the country or use hay shipped in from elsewhere, especially during the busy show season. Therefore, botulism is not restricted to one single region.
Other ways of preventing botulism include checking hay and grain for signs of decay and the presence of dead animals, which might contain the botulism toxin. If you use round bales for your horses, make sure they have been properly processed and are stored in an enclosed area. Hay bales stored outdoors should be kept off the ground on pallets, and they should not be wrapped in plasticâjust covered with a tarp. Rodent and bird control around the barn is also an integral part of prevention.
Read more about botulism on the Neogen website here