Tea-time tutorial: A concise guide to botulism

Botulism is a very severe paralytic illness caused by a nerve toxin produced by the bacterium Clostridium botulinum. It can be fatal if not spotted and treated early.

Food-borne botulism, the dominant form of the disease, is caused by ingestion of pre-formed toxin in food or a beverage. It usually occurs after ingestion of foods stored in airtight (i.e. anaerobic) containers. The incubation period is typically 12-36 hours but can be up to seven days.

In food-borne botulism, vomiting and diarrhoea, followed by constipation, might precede neurological symptoms:
• Disturbances to vision: blurred vision, double vision, drooping eyelids, dilated pupils
• Difficulty in swallowing and talking, slurred speech, dry mouth
• Descending muscle weakness
• Respiratory difficulty or failure due to respiratory muscle paralysis.

Urgent clinical actions

Patients who present with any of these GI or neurological signs and/or symptoms should be urgently referred as a suspected case of botulism.

Ways to catch botulism

Botulism spores are widespread in the environment and can be found in dust, soil, untreated water, and the digestive tracts of animals and fish. 

Foods that have led to botulism outbreaks have included meat products, such as sausage and cured ham; canned, vacuum-packed, smoked or fermented fish products; vegetables or fish preserved by canning or stored in oil; baked potatoes; honey; and cheese. 

Many outbreaks have also occurred in home-preserved foods.

Avoidance

There is no routine vaccination against botulism. Care should be taken when canning food, either commercially or at home, and when preserving fish, meat and vegetables to make sure the bacteria is destroyed before storage. 

Food in containers that are obviously bulging (which could be caused by gas from the botulinum) or which are damaged should not be eaten. Avoid tasting food that might be spoiled. Food that has not been completely processed should be kept in the fridge. Boiling food for 10 minutes before eating would inactivate the toxin in home-canned foods. 

Potential botulism cases should be investigated urgently. Food botulism does not spread from person to person.

More information

• gov.uk/government/publications/botulism-clinical-and-public-health-management
• nhs.uk/conditions/botulism

Source: UK Health Security Agency and European Centre for Disease Prevention and Control