For health professionals: Botulism

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What health professionals need to know about botulism

Botulism is a rare, severe neuroparalytic disease caused by accidental or intentional exposure to seven distinct botulism toxins (BoNTS, A to G types). Botulism affects humans and a variety of domestic and wild animals.

Botulism develops if:

  • a person ingests the toxin
  • the toxin is inhaled or injected
  • the organism grows in intestines or wounds and then releases toxin

There are 4 main forms of botulism:

  • infant
  • wound
  • food-borne
  • adult intestinal colonization

Clinical manifestations

Clinical manifestations are different depending on the form of botulism, though it is characterized by its classic triad:

  • a clear sensorium
  • the absence of fever
  • symmetric descending flaccid paralysis with prominent bulbar palsies (muscle paralysis)

Food-borne botulism

Food-borne botulism results from the ingestion of preformed neurotoxin in food or beverages.

Symptoms may initially include vomiting and/or diarrhea. They are followed by one or more of the following indicators of paralysis, beginning in the cranial nerves:

  • ptosis (drooping of eyelids)
  • dysphagia (difficulty in swallowing)
  • active mydriasis (dilated and fixed pupils)
  • dry mouth and dysphonia (difficulty speaking)
  • visual disturbance and diplopia (double vision)

These symptoms may extend to a descending symmetrical flaccid paralysis in an alert afebrile person.

Constipation is a common symptom later in presentation. The case-fatality rate is approximately 5% to 10%.

Wound botulism

Wound botulism results when a wound becomes infected with Clostridium botulinum and toxin is produced.

This form of botulism exhibits similar symptoms as food-borne botulism, except there’s no vomiting and/or diarrhea.

Infant botulism

Infant botulism results from ingestion of spores that germinate in the intestine and produce bacteria that release toxin.

This form of botulism affects infants younger than a year old, with most cases occurring between 6 weeks and 6 months old.

Clinical symptoms start with constipation and may include:

  • ptosis
  • drooling
  • hypotonia
  • a weak cry
  • a weak suck
  • loss of appetite
  • disconjugate gaze
  • generalized weakness
  • blunted facial expression
  • sluggishly reactive pupils
  • decreased anal sphincter tone
  • a significant loss of head control

Adult intestinal colonization botulism

Adult intestinal colonization botulism results when Clostridium botulinum germinates and produces toxin in the digestive system.

This form of botulism affects adults who have altered gastrointestinal anatomy and microflora. This can happen with:

  • intestinal surgery
  • inflammatory bowel disease
  • exposure to microbial agents

The symptoms observed are similar to food-borne botulism.


The Botulism Reference Service for Canada conducts the laboratory investigation.

Diagnosis of food-borne botulism is made by demonstration of botulinum toxin in:

  • serum
  • incriminated food

It can also be diagnosed through the isolation of Clostridium botulinum from stool or gastric aspirate.

Identification of the bacteria in a suspected food is helpful. However, in the absence of botulinum toxin, it’s not diagnostic because Clostridium botulinum spores are ubiquitous in the environment. Individuals may be diagnosed with foodborne botulism if they have symptoms and ate food linked to a laboratory-confirmed case of food-borne botulism.

The diagnosis of intestinal botulism is established through the identification of Clostridium botulinum organisms and/or toxin in a patient's feces or serum. This can be detected over an extended period of several days or weeks. Laboratory diagnosis is relevant for individuals who have no history of consuming a suspected food.

Wound botulism is diagnosed by:

  • evidence of a wound combined with detection of toxin in serum
  • isolation of Clostridium botulinum from a positive wound culture

Differential diagnoses of botulism include:

  • stroke
  • myasthenia gravis
  • Guillain-Barré syndrome


Individuals with clinically suspected botulism should be placed immediately in an intensive care setting and provided with:

  • botulinum antitoxin
  • supportive care, including mechanical ventilation if required

Antitoxin is most effective if given within 24 hours of the onset of symptoms.

In cases of wound botulism, the wound should be surgically debrided and drained. Antibiotics, usually penicillin, should be administered.

Surveillance in Canada

When a case of botulism is suspected, health care providers should notify:

Refer to the surveillance section for more information.

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