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Key Features

Essentials of Diagnosis

  • Dry mucous membranes

  • Diplopia; dilated, unreactive pupils

  • Descending paralysis

  • Difficulty in swallowing and speaking within 12–36 hours after ingestion of toxin-contaminated food

  • Multiple cases in a family or group

  • Hypotonia and constipation in infants

  • Diagnosis by clinical findings and identification of toxin in blood, stool, or implicated food

General Considerations

  • Botulism is a paralytic disease caused by Clostridium botulinum

    • Organism produces an extremely potent neurotoxin

    • Of the seven types of toxin (A–G), types A, B, and E cause most human diseases

    • The toxin, a polypeptide, is so potent that 0.1 mg is lethal for humans

  • Food-borne botulism usually results from ingestion of toxin-containing food

    • Virtually any food will support the growth of C botulinum spores into vegetative toxin-producing bacilli if an anaerobic, nonacid environment is provided

    • Food may not appear or taste spoiled

    • Toxin is heat-labile, but the spores are heat-resistant

  • Infant botulism

    • Occurs in infants younger than 12 months of age

    • Toxin is produced by ingested C botulinum spores that germinate and produce toxin in the gastrointestinal tract

  • Annually, 10–15 cases of wound botulism are reported; most cases occur in drug users with infection in intravenous or intramuscular injection sites

Clinical Findings

Symptoms and Signs

  • Presents with a "classic triad"

    • Afebrile

    • Symmetric, flaccid, descending paralysis with prominent bulbar palsies

    • Clear sensorium

  • Common bulbar palsies include the four "Ds"

    • Dysphonia

    • Dysphagia

    • Dysarthria

    • Diplopia

  • Food-borne botulism

    • Incubation period for is 8–36 hours

    • Lethargy and headache are initial symptoms

    • Double vision, dilated pupils, ptosis, and, within a few hours, difficulty with swallowing and speech follow

    • Mucous membranes often are very dry

    • Descending skeletal muscle paralysis may be seen

    • Death usually results from respiratory failure

  • Infant botulism

    • Initial symptoms are usually constipation and progressive, often severe, hypotonia

    • Loss of facial expression

    • Constipation

    • Weak suck and cry

    • Pooled oral secretions

    • Cranial nerve deficits

    • Generalized weakness

    • Apnea (on occasion)

Differential Diagnosis

  • Guillain-Barré syndrome

  • Poliomyelitis

  • Post diphtheritic polyneuritis

  • Certain chemical intoxications

  • Tick paralysis

  • Myasthenia gravis


Laboratory Findings

  • Diagnosis is made by demonstration of C botulinum toxin in stool, gastric aspirate or vomitus, or serum

  • Serum and stool samples can be sent for toxin confirmation (done by toxin neutralization mouse bioassay at CDC or state health departments)

  • In infant botulism

    • Serum assays for C botulinum toxin are usually negative

    • Tests take time and therapy should not be withheld awaiting testing results

  • Foods that are suspected to be contaminated should be kept refrigerated and given to public health personnel for testing

  • Laboratory findings, including CSF examination, are usually normal

  • Electromyography suggests the diagnosis if the characteristic brief, small abundant motor-unit action potentials (BSAP) abnormalities are seen

  • A nondiagnostic electromyogram does not exclude the diagnosis

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