Causes of botulism

Learn about the causes of botulism, how it’s spread and where it’s found.

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Causes of botulism

Botulism is a rare but serious disease. It is caused by a toxin produced by a specific type of bacteria.

How botulism is spread

Botulism is not spread from person to person.

You can get botulism from:

  • injection of illicit drugs
  • eating food or drinking beverages contaminated with the toxin

Infants (children under 1 year of age) can get botulism from eating honey containing spores of the bacteria.

Food-borne botulism

Food-borne botulism is caused by eating food or drinking beverages contaminated with the toxin.

Sources may include improperly:

  • prepared home-canned foods, such as:
    • beets
    • peppers
    • asparagus
    • mushrooms
    • green beans
  • stored food products, such as:
    • oil
    • garlic in oil
    • onions sautéed in butter
    • commercially prepared chili
    • commercially prepared cheese sauce
    • baked potatoes wrapped in aluminum foil stored at room temperature
  • traditionally prepared fish or marine mammal meat, such as:
    • seal
    • whale
    • walrus
    • salmon eggs
    • smoked or salted and un-gutted fish that is not refrigerated

Wound botulism

Wound botulism is caused by the bacteria getting into open wounds and producing toxin. Wound botulism is very rare and has never been reported in Canada.

However, wound botulism has been increasingly reported in other countries among injection drug users when using contaminated needles or impure heroin.

Infant botulism

Infant botulism happens when children under 1 year of age accidentally consume the spores of the bacteria. This can cause the bacteria to grow and produce toxin in the child’s intestinal tract.

Infant botulism is very rare in Canada, with fewer than 5 or 6 cases per year. In most cases of infant botulism, the botulism source is not found. Honey (both non-pasteurized and pasteurized) is the only identified source of infant botulism. It is recommended that honey only be fed to healthy children over 1 year of age.

Where botulism is found

The spores of the bacteria are widespread in nature and commonly found in:

  • soil
  • dust
  • sediments at the bottom of lakes and oceans
  • the intestines of animals, including fish and birds

These spores rarely cause problems because they do not grow when exposed to oxygen.

How food and beverages become contaminated

Food and beverages become contaminated when spores of the bacteria that cause botulism get into these products where they grow and produce toxins. Canned goods and other sealed food products provide ideal conditions for bacteria growth.

Commercial canned foods are processed at a high temperature to kill bacteria. These foods have an exceptionally good safety record.

Honey, the only known source of infant botulism, is contaminated with the spores, not the toxin.

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