Botulism is an often-lethal disease caused by a bacterial toxin. Although the disease can affect nearly all warmblooded animals, it is particularly deadly in horses, because they are more sensitive to the effects of the toxin than other animals.
Contaminated hay - One source of botulism
Botulism is characterized by neuromuscular blockade in which toxins block the communication between nerves and muscles and a flaccid paralysis that making it impossible for the horse to move.
The disease can strike suddenly and result in death in horses that were perfectly healthy the day before. Horsesâ best chance at survival lies in being treated with antitoxin as quickly as possible, but the disease often leaves no tangible footprint for veterinarians to detect through testing.
This makes it necessary to recognize the clinical signs that are suggestive of the disease and make the diagnosis on that basis alone.
Unless diagnosis can be made quickly and treatment provided in time to save the horse,the cause of the death may not be recognized.
Botulism is a disease characterized by neuromuscular blockade in which toxins block the communication between nerves and muscles and a flaccid paralysis that making it impossible for the horse to move, but the horse's body is not stiff.
How toxin attack the horse's system
The disease is not caused by the bacterium Clostridium botulinum, but rather by the toxins that it produces. Clostridial organisms are strict anaerobes, meaning they do not grow in the presence of oxygen or in healthy, well-oxygenated tissues.
Clostridium botulinum produces seven different neurotoxins (types A, B, C1 , D, E, F, and G), each of which is distinct and different enough from the others that antibodies against one type do not protect an animal against botulism from another type.
Botulinum toxin is one of the most potent biotoxins known and C. botulinum is a member of a family of lethal pathogens that are all capable of causing rapid, severe sickness and death. Tetanus, blackleg, and malignant edema are other diseases caused by members of the Clostridium genus.
3 ways horses are exposured to botulism toxins:
According to Kim Sprayberry, DVM, horses can get botulism toxin in three basic ways: ingestion of toxins, ingestion of the bacterium and internal production of toxins, and wounds.
The first mechanism of entry is ingestion of preformed toxin in feed. When horse are exposed to botulism toxin in the feed in this manner, the disease is sometimes called âforage poisoning,â usually involving type C toxin.
The toxin might be present as a contaminant in feed, or if there are droppings or carcasses of small rodents in the feeder or water tub. One problem occurs when rodents or other animals die in a field of forage, and
a carcass is incorporated into a bale during baling.
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 dried out or is unrecognizable in a flake of hay, enough spores can
remain to kill a horse.
Hay contaminated with animal carcasses is not the only route of foodborne exposure; the vegetation itself can also be a problem. When foodstuffs are improperly cured or dried, an anaerobic environment favorable for growth of the organism can develop. Anaerobic conditions can arise in wilted grass or vegetables, for example, and also in round hay bales.
Outbreaks of botulism have been associated with feeding discarded produce (wilted unsold lettuce at afarmerâs market in one instance) and lawn clippings.
Toxico infectious botulism is the second-most common form of botulism in horses, and this arises when the bacterium itself is ingested from soil and colonizes the gastrointestinal tract. As it grows inside the body, it produces the toxin, and signs of disease become apparent as toxin is absorbed into the bloodstream from the intestinal tract.
Clostridium botulisum type B predominates in the midwestern and Atlantic seaboard states, and it causes a manifestation of toxico infectious botulism called shaker foal disease. Shaker foal disease is a form of botulism that affects young foals, and it is mostly a problem in foals born to dams that were recently moved to an endemic area or that were not vaccinated during pregnancy.
The disease takes its name from the muscle trembling seen in affected foals.
Wound botulism is the third and least common form of botulism in horses. Deep puncture wounds or wounds in which tissue becomes devitalized can support growth of C. botulinum. When the bacterium grows and produces toxin, the toxin is absorbed into the bloodstream and the horse develops botulism.
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