botulism

Last edited 07/2023 and last reviewed 08/2023

Botulism is an extremely severe form of food poisoning due to ingestion of a preformed neurotoxin - botulin - from the spore-bearing anaerobe Clostridium botulinum (gram-positive bacilli). Types A, B and E most commonly produce disease in man. Types F and G are rare causes of botulism in humans.

The organism may be found in any food except for acid fruits which inhibit germination. Canned foods which have been incompletely sterilised are commonly implicated. Traditionally, home-bottled vegetables are a prime cause in the U.K.

The toxin prevents the presynaptic release of acetylcholine causing paralysis through its action at neuromuscular junctions; other clinical manifestations largely result from its actions at parasympathetic terminals:

• botulism toxin causes muscle weakness or paralysis, starting at the head and moving down the body
• symptomatology associated with botulism can include blurry or double vision, slurred speech, difficulty swallowing, shortness of breath, and paralysis of the arms and legs
• infants with botulism may present with features such as poor feeding, constipation, weak cry, and difficulty breathing
• foodborne botulism can present with nausea, vomiting, diarrhea, and abdominal pain

Causes:

• Clostridum botulinum neurotoxin
• Cases also associated with neurotoxin produced by Clostridium butyricum and Clostridium baratii

Reservoir:

• widespread in the environment – C. botulinum heat resistant spores exist in soil, dust, untreated water and the gastrointestinal tracts of animals and fish. Under the appropriate anaerobic conditions, the spores germinate and produce toxin

Epidemiology:

• Rare: 100-200 cases reported in the EU annually
• Three naturally occurring forms of botulism: food-borne, wound and infant (or intestinal) botulism. Inhalation botulism is extremely rare.

Transmission of botulism:

• Foodborne: ingestion of food contaminated by toxin. A variety of meat, fish and vegetables have been implicated. Associated with under processed food, and home preservation
  
  
• Wound: inoculation of spores that germinate in the tissue producing toxin and capable of causing systemic symptoms
  • occurs when C botulinum gets into a wound and produces botulism toxin inside the wound. People who inject illicit drugs (such as heroin) into their skin or muscles are at risk of developing wound botulism (2)
    
    
• Infant: ingestion of C. botulinum spores in food (e.g. in honey) or from the environment which germinate and produce toxin in the infant intestine. Persons with open lesions on their hands should wear gloves when handling soiled diapers from these patients. Cases of infant botulism caused by C. butyricum have been associated with pet terrapins in the UK and Ireland
  • occurs when newborns or infants ingest dust or soil containing C botulinum, which settles inside the gastrointestinal tract and then produces botulism toxin (2)
    • a less common source of infant botulism is raw honey
      
      
• Person-to-person spread does not occur in food or wound botulism. There is a risk of cross-infection to other infants with infant botulism due to excretion of organisms in faeces which may be prolonged. Stools should be discarded as hazardous material. Cross-infection control measures include scrupulous hand washing when handling infants and during nappy changing and avoiding close contact with other infants, including not sharing toys, bedding and cots

Incubation period:

• Foodborne: 2 hours to 8 days (usually 12-72 hours). More severe disease may be associated with a shorter incubation period
• Wound botulism: 4-21 days
• Inhalation: few hours to 4 days

Infectivity: C. botulinum may be detected in the stool and although person- to-person spread does not occur for food or wound botulism, in infant botulism, cross-infection control measures should be followed

Reference:

• PHE (2019). Recommendations for the Public Health Management of Gastrointestinal Infections
• Jin J. What Is Botulism? JAMA. 2023;330(1):90. doi:10.1001/jama.2023.8085