Botulism is a dangerous disease caused by infection with the bacteria Clostridium botulinum. The bacteria produces toxins which target the nervous system causing muscle weakness and paralysis. If the condition is not treated, the paralysis can reach the lungs and cause respiratory failure.
Botulism can be divided into three main types:
- Food-borne botulism – Food can get contaminated with C. botulinum from infected soil. If the food is not adequately cooked or preserved, the bacteria start to produce the toxins.
- Infant botulism – This occurs in infants aged less than one year old who ingest the bacteria, which goes on to produce the toxin inside the infant’s intestines. Infants aged older than one year have bacteria in their gut that prevent C. botulinum from producing the toxins.
- Wound botulism – This occurs when a wound gets infected with C. botulinum due to sniffing or injecting contaminated drugs.
How is botulism spread?
C. botulinum commonly occurs in soil and water, where it can live for long periods of time. In the presence of low oxygen levels and favorable temperatures, C. botulinum produces the botulinum toxin. This toxin is normally destroyed by heat but if the food is not adequately cooked, the toxin may be ingested. Wound botulism usually occurs among people who inject street drugs. The spores enter a wound and go on to release the toxin.
Symptoms of botulism
The symptoms of food-borne botulism may develop within as little as 6 hours to as much as 8 days after exposure to the toxin. The initial symptoms usually include nausea, diarrhea and vomiting. Around 12 to 36 hours after exposure, symptoms of neurological involvement may develop such as slurred speech, double vision, muscle weakness and paralysis.
In the case of wound botulism, symptoms may take 4 to 14 days to manifest, starting in the cranial nerves and then gradually involving other parts of the body as the toxic effects increase. The neurological symptoms of wound botulism can take longer to develop than in food-borne botulism, although they are similar between the two types. Symptoms that involve the nervous system in wound botulism include double vision, facial weakness, dry mouth, difficulty swallowing and slurred speech.
Infant botulism becomes symptomatic between 3 and 30 days after ingesting the bacteria. Initially, the infant may be constipated, refuse to feed and seem sluggish. This is followed by more serious symptoms such as reduced muscle tone, poor reflexes and an inability to suck.
Diagnosis and treatment
Botulism may be suspected based on a patient’s symptoms and the details they give of any possible exposure to C. Botulinum. A diagnosis can be confirmed using a stool or wound sample and the patient is administered an antitoxin to prevent progression of the illness. Antitoxins are antibodies that can neutralize the toxin by blocking its effects on the nervous system. If required, a patient is given breathing support using a ventilator and provided with nutrients and fluids using an intravenous drip.
In the UK, the risk of becoming infected with botulism is significantly reduced if certain health and safety practices are followed. Examples include:
- Maintenance of food hygiene
- Adequate food refrigeration
- Baked potatoes that have been baked while wrapped in aluminium foil must be kept hot until served or refrigerated
- Foods that could be contaminated should be cooked or reheated at high temperatures, to destroy any botulism toxin
- Babies aged under 1 year should not be given honey or corn syrup as these have been reported to contain the C.botulinum spores.
- If drug users cannot avoid using the drug, they should inject it into a vein rather than a muscle or smoke the substance.
Reviewed by Sally Robertson, BSc