Botulism Clinical Presentation

Updated: Dec 07, 2022
  • Author: William N Bennett, V, MD; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Following the onset of symptoms, botulism quickly progresses over several days. The magnitude of the neuromuscular impairment can advance hourly. Persons who survive this phase eventually stabilize and then recover over a period of days to months. The mechanism of recovery is not fully understood but requires the generation of new presynaptic axons and the formation of new synapses, as the original synapses are permanently affected. As with tetanus, recovery from botulism does not confer long-term immunity. Rare reports have described a second episode in the same patient.

Foodborne botulism

Foodborne botulism should be suspected in patients who present with an acute gastrointestinal illness associated with neurologic symptoms. Symptoms a median of 1 day following consumption of contaminated food produc. [23]  The severity of the illness varies from mild to severe, and death occurs at a median of 3 days after hospitalization. The modern case fatality ratio is 9%.

Wound botulism

Patients with wound botulism typically have a history of traumatic injury with wounds that are contaminated with soil. [24]

Since 1994, the number of patients with wound botulism who have a history of chronic intravenous drug abuse has increased dramatically. In most cases, black-tar heroin has been the implicated vehicle. A study by Yuan et al followed 17 heroin users who had recurrent botulism after using black-tar heroin. [13]  Physicians need to be alert to recognize botulism, especially in patients who use black-tar heroin or in those with a history of injection drug–associated botulism.

Rare cases of wound botulism after cesarean delivery have been documented. [14]

Aside from a longer incubation period, wound botulism is similar to foodborne botulism. The incubation period of wound botulism ranges from 4-13 days, with a median 6.5 days. [15]  Unlike foodborne botulism, gastrointestinal symptoms (including nausea, vomiting, diarrhea) are uncommon in wound botulism. Patients may be febrile, but this is more likely due to the wound infection rather than the wound botulism. In many cases, the wound appears benign.

Adult intestinal toxemia

Adult intestinal toxemia results from enteric colonization with C botulinum that progresses to toxin production. The pathophysiology of the changes in the gastrointestinal flora that facilitate colonization is unclear. [25]

Iatrogenic botulism due to accidental overdose of botulinum toxin (Botox or Dysport)

Cases of botulism due to Botox overdosage have been reported. Symptoms vary and can include dysphagia, ptosis, and diplopia, as well as more severe presentations of systemic weakness or muscle paralysis. [26]



Almost all patients with foodborne or intestinal exposure are afebrile and the majority of patients will display descending paralysis with cranial nerve palsies early in the disease process.  A collection of anticholinergic toxicity symptoms will present such as nausea, vomiting, dysphagia, diplopia, dilated/fixed pupils, and dry mouth. [9]  Mydriasis is seen in 50% of cases.

Generally, botulism progresses as follows:

  • Preceding or following the onset of paralysis are nonspecific findings such as nausea, vomiting, abdominal pain, malaise, dizziness, dry mouth, dry throat, and, occasionally, sore throat. Except for nerves I and II, the cranial nerves are affected first.

  • Cranial nerve paralysis manifests as blurred vision, diplopia, ptosis, extraocular muscle weakness or paresis, fixed/dilated pupils, dysarthria, dysphagia, and/or suppressed gag reflex. Additional neurologic manifestations include symmetric descending paralysis or weakness of motor and autonomic nerves.

  • Respiratory muscle weakness may be subtle or progressive, advancing rapidly to respiratory failure. Progressive muscle weakness occurs and often involves the muscles of the head and neck, as well as intercostal diaphragmatic muscles and those of the extremities.

The autonomic nervous system is also involved. Manifestations of this include the following:

  • Paralytic ileus advancing to severe constipation

  • Gastric dilatation

  • Bladder distention advancing to urinary retention

  • Orthostatic hypotension

  • Reduced salivation

  • Reduced lacrimation

Other neurologic findings include the following:

  • Changes in deep tendon reflexes, which may be either intact or diminished

  • Incoordination due to muscle weakness

  • Absence of pathologic reflexes and normal findings on sensory and gait examinations

  • Normal results on mental status examination



Wound botulism

Causes of wound botulism have been associated with traumatic injury involving contamination with soil, chronic abuse of intravenous drugs (eg, black-tar heroin), and rarely cesarean delivery. Wound botulism illness can occur even after antibiotics are administered to prevent wound infection.  Wound botulism from black-tar heroin use has primarily occurred in California. [16]

Foodborne botulism

Of the roughly 110 cases of botulism that occur in the US annually, foodborne exposure accounts for ~25% of cases. [16]   It results from the ingestion of preformed neurotoxins; A, B, and E are the most common.  California, Washington, Colorado, Oregon and Alaska, have accounted for >50% of reported foodborne outbreaks in the US since 1950.

High-risk foods include home-canned or home-processed low-acid fruits, vegetables, fish and fish products (neurotoxin serotype E). [20]

Commercially processed foods and improperly handled fresh foods are occasionally associated with botulism outbreaks.  The type of food responsible for approximately 28% of outbreaks remains unknown.