Botulism Kills 23 Horses in Maine


A rare botulism outbreak caused the deaths of 23 horses at the Whistlin’ Willow farm in Gorham, Maine.



The 175-acre farm lost 23 of its horses between April 7 and 17 due to the fast- acting Botulinum neurotoxin. State inspectors believe the animals became sick after ingesting poisoned bales of silage. Silage, unlike hay, is a type of fodder for livestock that remains moist through a specific fermentation process. This makes it more vulnerable to the development of toxins. Thankfully, the remaining 40 to 45 horses at the farm were unaffected by the outbreak.

Dr. Donald Hoenig, the veterinarian involved in the case, explains that little can be done once a horse exhibits symptoms of botulism poisoning. Although antidotes are available, administering them requires the veterinarian to know which of the eight different strains of botulism caused the poisoning. Further, the antitoxin can cost up to $1,000 per dose.

No other unusual deaths in horses have been reported in Maine, and nearby horse owners expressed no concern about the welfare of their animals. “There is no panic that this would spread,” says Jo Hight, president of the Maine Horse Association.

Although the botulinum bacteria cannot spread through water, state officials are worried about the potential runoff of other contaminants into wetlands or streams.

To ensure that surrounding water sources remain unpolluted, state officials worked with the farm owners to properly dispose of the animal carcasses. The horses were buried 8 feet deep, far below the water table.


Clostridium botulinum

Clostridium botulinum is a type of bacterium that produces a number of potent neurotoxins. The bacterium is commonly found in food items that were incorrectly processed. There are eight different types of recognized botulism; Types B and C are most commonly associated with poisonings in horses.

Clostridial disease in horses is often characterized by muscle failure and difficulty eating, breathing, and swallowing. Since the horse’s respiratory muscles eventually become paralyzed, few cases survive botulism poisoning. However, an effective vaccine against C. botulinum type B is available for use in horses within the United States. 

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