Last reviewed: 28 Oct 2020
Last updated: 28 Mar 2018



History and exam

Key diagnostic factors

  • presence of risk factors
  • blurred vision and diplopia
  • impaired accommodation
  • ptosis
  • oculobulbar weakness
  • hypoglossal weakness
  • dysarthria
  • dysphagia
  • symmetrical descending flaccid paralysis

Other diagnostic factors

  • hypotonia
  • feeding difficulties in infants
  • weakened cry in infants
  • hypothermia
  • urinary retention
  • constipation
  • dry mouth and throat
  • postural hypotension
  • gastrointestinal illness
  • diminished or absent deep tendon reflexes
  • absence of fever
  • respiratory dysfunction
  • pupillary dilation

Risk factors

  • ingestion of contaminated foods
  • ingestion of honey in infants
  • ingestion of soil in infants
  • intravenous drug use
  • crush injury
  • infant age group
  • abnormal bowel anatomy
  • therapeutic or cosmetic use of botulinum toxin
  • biological terrorism
  • exposure to reptiles

Diagnostic investigations

1st investigations to order

  • mouse bioassay of serum, gastric secretions, stool, or food samples
  • culture of food samples, gastric aspirates, or faecal material
More 1st investigations to order

Emerging tests

  • enzyme-linked immunosorbent assay (ELISA)
  • polymerase chain reaction (PCR)
More emerging tests

Treatment algorithm


Linda S. Nield

Professor of Pediatrics

West Virginia University School of Medicine




LSN is an author of a reference cited in this topic.

Dr Linda Nield would like to gratefully acknowledge Dr Thomas P. Bleck, Dr Aimee Hodowanec, Dr Pavani Reddy, and Dr Teresa Zembower, previous contributors to this topic. TPB, AH, PR, and TZ declare that they have no competing interests.

Peer reviewersVIEW ALL

Research Fellow and Medical Microbiologist

Wellcome Trust Sanger Institute

Department of Microbiology

Addenbrooke's Hospital




FC declares that she has no competing interests.

Assistant Professor of Medicine

Division of Infectious Diseases

University of Vermont College of Medicine




CDH declares that he has no competing interests.

Chief and Professor of Medicine

Division of Infectious Diseases and International Health

University of Virginia Health System




WAP declares that he has no competing interests.

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