General Information - Botulism

What is botulism?

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

What is its bioterrorism potential?

Botulinum toxin is the most poisonous substance known. Several countries are known to have attempted weaponisation of the toxin for airborne dispersal (which would lead to toxin inhalation). Food-borne dispersal would also be possible. Water-borne dispersal is unlikely due to the rapid neutralisation of the toxin by standard water treatment procedures.

How do you catch botulism?

In most cases, the symptoms are caused not by the organism itself, but by eating or breathing in the toxin. A deliberate release of botulinum toxin would most likely be via the airborne (inhalation) route or through contamination of foods. Intestinal and wound botulism would be unlikely following a deliberate release of toxin. Botulism cannot be caught from an affected or infected person.

• Food-borne botulism occurs when the spores of Clostridium botulinum have germinated and the bacteria have reproduced in an environment (foodstuff) outside the body and produced toxin. The toxin is consumed when the food is eaten. C. botulinum is an 'anaerobic bacterium' which means it can only grow in the absence of oxygen; botulism is often associated with home-preserved foods, especially those preserved in oil. A very wide range of food items has been implicated. The toxin is destroyed by normal cooking processes.
• Inhalation botulism is extremely rare; only three cases are known to have occurred.
• Intestinal colonisation botulism usually occurs in infants (less than 2 years of age) and is extremely rare. It occurs following ingestion of spores that then germinate and produce bacterial cells; these then release 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. This form of botulism is seen in injecting drug users.

How long can you have the infection before developing symptoms?

Symptoms usually occur between 12 and 36 hours after ingesting toxin from contaminated food. Symptoms can occur as early as 6 - 8 hours or as late as 8 days depending on the type and dose of toxin.

What are the symptoms?

Symptoms often begin with blurred vision and difficulty in swallowing and speaking, but diarrhoea and vomiting can also occur. The disease can progress to paralysis. Most cases will recover, but the recovery period can be many months. The disease can be fatal in 5-10% of cases; death is due to respiratory failure.

How can botulism be treated?

Antitoxin is available which acts as an "antidote" against the toxin; it must be given as soon as possible for best results. It will prevent the patient from worsening, but recovery is still slow. In addition, treatment will focus on tackling the symptoms, such as supporting ventilation in the event of respiratory failure.

How can botulism be prevented?

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

How common is botulism?

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

Last reviewed: 1 April 2009