Botulism

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

Diagnosis

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