Botulism - Frequently asked questions

What is botulism?

Botulism is caused by a botulinum toxin, which is a poison produced by the bacterium Clostridium botulinum. The bacterium is common in the soil in the form of spores.

What are the symptoms?

Symptoms often begin with blurred vision and difficulty in swallowing and speaking, but sometimes diarrhoea and vomiting can occur. The disease can go on to lead to further problems with vision, and paralysis. Most cases make a recovery, but the recovery period can be many months. The disease can be fatal in 5-10% of cases.

How do you catch botulism?

The symptoms are caused not by the organism itself, but by eating or breathing in the toxin which the organism releases.

Foodborne botulism occurs when the spores of the organism Clostridium botulinum have germinated and the bacteria have reproduced in an environment outside the body and produced toxin - this environment is usually a foodstuff. The adult then consumes the toxin itself when they eat the food, and this makes them ill with weakness and paralysis. Clostridium botulinum is an "anaerobic bacterium" which means it can only grow in the absence of oxygen, so botulism in adults tends to occur when the spores have somehow got into an airtight environment such as tins or jars, particularly home-preserved foods which have been preserved in oil.

The toxin is destroyed by normal cooking processes.

Infant botulism is extremely rare but occurs when the baby ingests spores which germinate to produce the bacterial cells that reproduce in the gut and release toxin. In most adults and older children, this would not happen because the natural defences which have developed in an adult gut would prevent the germination and growth of Clostridium botulinum. In some babies, these defences have not yet developed, and so this gives the infection a chance to get a foothold and produce the toxin.

Wound botulism has the same symptoms as other forms, but occurs when the organisms get into an open wound and are able to reproduce in an "anaerobic" environment.

How long can you have the infection before developing symptoms?

It is usually a matter of 12-36 hours between exposure to the toxin and the development of symptoms. In infant botulism, some time may elapse between ingestion of the spores and the release of the toxin.

How can botulism be prevented or treated?

Antitoxin is available which can be given to a patient as an "antidote" to tackle the toxin. In addition, treatment will focus on tackling the symptoms, such as supporting ventilation in the event of respiratory failure.

There is a vaccine against botulism, but there are concerns about its effectiveness and it also has side effects, and so it is not widely used.

How common is botulism?

Naturally occurring botulism is very rare in the UK; it is more common in the USA but even there the disease is not widespread.

Last reviewed: 15 August 2008