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Potentially life-threatening emergency
Other Resources UpToDate PubMed
Potentially life-threatening emergency


Contributors: Lewis Rubinson MD, PhD, David R. Lane MD
Other Resources UpToDate PubMed


This summary discusses adults and children. Botulism in infants is addressed separately.

Botulism is caused by a group of paralytic neurotoxins produced by the spore-forming anaerobic gram-positive bacillus Clostridium botulinum. Botulinum toxin irreversibly binds to the pre-synaptic cholinergic neuromuscular junction, blocking acetylcholine release and manifesting as a symmetric progressive descending flaccid paralysis with bulbar palsies after an 18- to 72-hour incubation period. Multiple cranial nerve palsies are evident early in the course of the disease. Symptom severity ranges from mild to frank paralysis. Botulism has a mortality rate of 5%-10% (up to 30% in victims over 60 years of age).

Intoxication can occur naturally from contaminated foods or rarely as a result of wound or intestinal colonization in humans. There are 7 types of botulinum toxins, A through G, although only A, B, E, and F have been implicated in the poisoning of humans. Botulinum toxins are odorless and colorless in solution. Botulism is not spread person to person.

People at higher risk for contracting food-borne botulism are nursing home residents, dormitory residents, wedding guests, and large event attendees. Intestinal botulism occurs in infants, and wound botulism must be suspected in IV drug users, particularly black tar heroin users, who present with weakness (in addition to cerebral infection or epidural abscess).

In food-acquired cases, nausea, vomiting, and diarrhea may precede the paralysis, and cases will cluster around consumption of the contaminated food at a restaurant or from improper home canning.

Patients are afebrile with initial complaints of blurred vision, diplopia, and mydriasis with photophobia, ptosis, ophthalmoplegia, hoarseness, dysarthric speech, and dysphagia. Constipation, dry mouth, and urinary retention may also occur. Patients remain awake, alert, and oriented throughout the entire illness. Symptoms progress in a descending pattern to produce a skeletal muscle paralysis that may cause sudden respiratory arrest and death if untreated. Severe poisonings may require months of ventilatory support.

If you have high suspicion for botulism, it is imperative to notify public health officials immediately. They will assist with gauging the likelihood of disease and are the only group who can release the antidote (an antitoxin). Best available data suggests that antitoxin, when administered early, is associated with better clinical outcomes. Antitoxin is available from the US Centers for Disease Control and Prevention (CDC).

Botulinum Toxin and Bioterrorism
Botulism is classified as a Category A bioterrorism agent because of its ease of dissemination and high mortality rate. When used as a biological weapon, botulinum toxin is most likely to be dispersed as an aerosol for inhalation, although it could be added to the food or water supply. Following an aerosol release, the toxin may be swallowed as well as inhaled.


A05.1 – Botulism food poisoning

398565003 – Botulism

Look For

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Diagnostic Pearls

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Differential Diagnosis & Pitfalls

  • Myasthenia gravis (antibody studies most useful; false positive edrophonium tests have been reported with botulism)
  • Snake bite (eg, Pit viper snake envenomation, Coral snake envenomation)
  • Tick paralysis (inspect all skin looking for tick)
  • Mushroom poisoning
  • Central nervous system (CNS) infection (eg, Encephalitis, Bacterial meningitis, Brain abscess)
  • CNS tumor
  • Cerebral stroke
  • Drug overdose (depressants, atropine)
  • Acute inflammatory demyelinating polyneuropathy (ascending paralysis)
  • Lambert-Eaton myasthenic syndrome
  • Marine toxins (tetrodotoxin, Saxitoxin poisoning)
  • Organophosphate poisoning (mydriasis, copious secretions, and in some cases confusion and seizures)
Multiple / many patients with weakness:
  • Nerve agent poisoning (mydriasis, copious secretions, and in some cases confusion and seizures)

Best Tests

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Management Pearls

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Drug Reaction Data

Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.

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Last Updated:01/09/2019
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Potentially life-threatening emergency
Patient Information for Botulism
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Potentially life-threatening emergency
A medical illustration showing key findings of Botulism : Diplopia, Dysarthria, Eyelid ptosis, Flaccid paralysis, Dysphagia, Dysphonia
Illustration image of Botulism - imageId=1314097. Click to open in gallery.
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