What is botulism?
Botulism is a rare but serious illness caused by a toxin produced by the bacterium Clostridium botulinum. There are three main forms of botulism:
- Foodborne botulism – Occurs when a person ingests pre-formed botulinum toxin in contaminated food
- Wound botulism – Caused when wound is infected with Clostridium botulinum that secretes the toxin
- Infant botulism – Affects babies under 12 months who have C. botulinum in their intestinal tract
Foodborne botulism is the most common form of botulism accounting for 15% of all cases. It occurs when someone ingests food contaminated with the botulinum toxin. Home-canned foods are a common source of contamination. Symptoms usually begin 18 to 36 hours after ingesting the toxin, but can appear as early as 6 hours or as late as 10 days.
What are the symptoms of botulism?
The initial symptoms of botulism include:
- Blurred or double vision
- Drooping eyelids
- Slurred speech
- Difficulty swallowing
- Dry mouth
- Muscle weakness
Without treatment, botulism can progress and cause:
- Paralysis of the arms, legs, trunk and respiratory muscles
- Respiratory failure
- Dangerously low blood pressure
Infant botulism specifically causes poor feeding, weakness, constipation and a distressed cry in babies. Wound botulism can initially cause fatigue and weakness around the infected wound.
How is botulism diagnosed?
A physician may suspect botulism based on a patient’s symptoms and recent food history. However, laboratory tests are needed to confirm the diagnosis:
- Detection of botulinum toxin in stool, serum, gastric aspirate or vomitus sample
- Culture for C. botulinum bacteria from feces or infected wound
- Electromyography (EMG) to measure muscle response – helps confirm clinical diagnosis
Distinguishing botulism from stroke, myasthenia gravis, Guillain-Barre syndrome and tick paralysis requires confirmatory lab tests.
What is the treatment for botulism?
The mainstays of botulism treatment are:
- Antitoxin – An injectable antibody that neutralizes toxin molecules that are unbound to nerve endings
- Supportive care – Respiratory support if needed, IV fluids, nutritional support
- Wound care – Debridement and antibiotics for wound botulism
Antitoxin should be administered as soon as possible after suspective ingestion or inhalation of toxin. It is most effective if given within 24 hours of toxin exposure. Wound botulism requires surgical debridement and antibiotics directed at C. botulinum bacteria.
What is the mortality rate for botulism?
Botulism used to have a mortality rate as high as 60% in the early 20th century. However, with current supportive care and antitoxin therapy, the case fatality rate has now dropped to less than 10%.
Infant botulism has an even lower case fatality rate of less than 1%. Wound botulism has a 5-10% fatality rate. Foodborne botulism mortality varies based on patient age, subtype of C. botulinum toxin and delay in diagnosis and treatment.
Here is a summary of approximate botulism mortality rates:
| Type | Mortality Rate |
|---|---|
| Foodborne botulism | 5-10% |
| Wound botulism | 5-10% |
| Infant botulism | <1% |
| Adult intestinal toxemia | 15-20% |
Factors affecting botulism mortality
Several factors influence the mortality rate in botulism patients:
- Patient’s age – Mortality is higher in older adults
- Delay in diagnosis and antitoxin administration
- Subtype of C. botulinum toxin – Type A, B and E are most lethal
- Dose of toxin ingested – Higher dose means higher mortality
- Mode and site of toxin exposure – Inhalation and wound botulism have higher death rates
- Access to mechanical ventilation – Required in severe cases
What is the long-term outlook for botulism survivors?
With aggressive supportive care, most botulism patients will recover fully. However, the recovery is often slow over several weeks to months. Patients can suffer from:
- Fatigue
- Shortness of breath
- Limb weakness
- Difficulty swallowing
Factors that can prolong recovery include:
- Advanced age
- Delay in diagnosis and antitoxin administration
- Prolonged mechanical ventilation
- High dose of toxin ingested
With rehabilitation involving physical and occupational therapy, full strength and functional recovery is possible in most survivors.
Can botulism be prevented?
Preventative measures for botulism include:
- Proper home canning – Following instructions precisely
- Not feeding honey to infants <12 months
- Proper food handling and storage
- Careful wound care
- Vaccination – Available for high risk adults like lab workers
Public health officials should be notified immediately if a case of botulism is suspected. The source of contaminated food must be identified and recalled.
For wound botulism, intravenous drug users should use sterile technique and avoid injecting into muscle or skin.
Conclusion
Botulism is a rare but potentially fatal illness if left untreated. The culprit is a nerve toxin produced by Clostridium botulinum bacteria. While historical mortality rates were as high as 60%, modern medicine has dropped the death rate to less than 10%.
With prompt diagnosis, antitoxin administration and vigilant supportive care, the vast majority of botulism patients will survive with full recovery over time. Public health measures to prevent food contamination remain crucial. Botulism serves as a reminder that while medical advances have come far, ancient bacteria like C. botulinum still pose a lethal threat.