Conditions or ailments that are the cause of a problem that you see - your observation.

Your vet may diagnose


Synonyms: Bulbar Paralysis, Lamziekte, Limberneck, Loin Disease, Shaker Foal Syndrome, Western Duck Sickness


Botulism is caused by a potent toxin produced by the bacteria Clostridium botulinum. This bacteria is anaerobic, meaning it only lives where there is no oxygen and can be found in soils, wounds and decaying organic material. The spores of this bacteria can lie dormant in the environment for years and can tolerate climate extremes. Under the right conditions, the spores become active and produce a very potent toxin.

There are several types of toxins, all of which cause similar symptoms but which come from different sources. Either the toxin itself is ingested (type B or C) and absorbed in the intestine, the bacteria is ingested and the toxin is formed in the intestine (type B), or the bacteria grows in an infected wound and the toxin taken up by the blood stream.

Signs of intoxication include progressively worsening muscle weakness, and ultimately paralysis, resulting in a down horse that cannot rise. Classic signs are very slow eating and lack of tongue strength.

Botulism is hard to definitively diagnose, and is often diagnosed by exclusion of other diseases.

In Shaker Foal Syndrome (type B), foals ingest botulinum spores from the soil. The spores grow in the intestine, forming the toxin that gains access to the bloodstream. This condition is most common in the mid-Atlantic States, especially Kentucky.

my vet's role



Other conditions or ailments that might also need to be ruled out by a vet.

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The prognosis for most Botulism cases is grave without aggressive treatment. Once a horse cannot rise, the prognosis is very poor and euthanasia should be considered. Some mildly affected horses may be maintained with nursing care and feeding tube until they gradually recover.

my role


I might observe

You might make these observations when a horse has this condition.

Very Common
Less Common
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Questions To Ask Your Vet:
  • Is hyperimmune plasma of any use in this case?
  • Where do you think the horse acquired the infection?

  • What type of botulism is this?

Provide horses with high quality hay and immediately remove dead carcasses from their environment. Talk to your vet about the Botulism vaccine. Recognize that there is increased risk in large bale feeding, haylage and sileage feeding.

A vaccine is available for Type B. The Shaker Foal syndrome is prevented by vaccinating late-term pregnant mare with the Type B vaccine. Vaccination for Type C is extra-label use of a mink vaccine.

Botulism has been linked to the feeding of fresh grass clippings, which can foster the growth of spores if left to decompose prior to feeding.

Related References:

Lavoie JP, Hinchcliff KW eds. Blackwell's 5 Minute Vet Consult: Equine. 2nd Ed. Ames: Wiley Blackwell 2008.

Author: Doug Thal DVM Dipl. ABVP