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    Infectious Diseases A-Z: Foodborne botulism basics

a person canning vegetables in jars
Foodborne botulism is often associated with improper home canning techniques. But what is botulism, and why is it a concern?

Botulism was first written about in Germany in 1735. It was linked to sausages (from the Latin botulus “sausage"). To this day, foodborne botulism continues to cause serious illness and death.

"Botulism is a type of foodborne illness that is caused by a toxin produced by a bacteria called Clostridium botulinum," says Dr. Nipunie Rajapakse, a Mayo Clinic infectious diseases specialist. “The toxin is released in food. If you ingest a food that contains this toxin, it can cause you to become quite unwell. The main symptom is paralysis. Usually, the signs of paralysis start at the top. So one of the first symptoms that we see in patients with botulism poisoning usually is drooping of the eyelids. It also involves paralysis of breathing muscles. And, if it spreads to that level, patients often end up in an intensive care setting on a ventilator for management of that."

Watch: Dr. Nipunie Rajapakse explains foodborne botulism.

Where botulism is found?

"The most common place that we find foodborne botulism is in canned goods," says Dr. Rajapakse. "The Clostridium botulinum bacteria that produces this toxin likes to grow in environments where there’s no oxygen, and canning is a process whereby you remove oxygen from the environment. And, so it likes to thrive in that type of environment. Home canned or jarred goods are usually the culprit that’s found in most outbreaks. There are pretty strict standards for commercially-prepared products that are in place to help protect us from this type of infection."

How to prevent botulism

Dr. Rajapakse says one of the issues with this bacterium is that it forms spores that resist to heating and can survive in a dormant state even if heated to high temperatures. She says that's why it’s especially important to ensure that you really know what you’re doing if you’re canning, preserving or fermenting foods at home. And when shopping at the grocery store for canned vegetables or fruit, avoid any cans that look like they’re bulging or misshapen, including if they look dented or bent in any way. Dr. Rajapakse says it can be a sign that there is a problem with the food that is contained within it, although sometimes it’s unrelated.

Most common forms of botulism

  • Foodborne botulism
    The harmful bacteria thrive and produce the toxin in environments with little oxygen, such as in canned food.
  • Wound botulism
    If these bacteria get into a cut, they can cause a dangerous infection that produces the toxin.
  • Infant botulism
    This is most common form of botulism. It begins after Clostridium botulinum bacterial spores grow in a baby's intestinal tract. This type of botulism typically occurs between 2 and 8 months, and has classically been associated with the ingestion of honey. This is why honey should not be given to children younger than 12 months.

Botulism may be treated with an antitoxin that reduces the risk of complications.

"If the infection is diagnosed, there is treatment; however, oftentimes the infection is not diagnosed until quite late in a patient’s presentation just because there are other conditions or illnesses that can look quite similar." says Dr. Rajapakse. "It’s really important that it’s recognized early and that treatment is given early to have the best outcomes."