What is botulism?

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

What is its bioterrorism potential

Botulism 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. Waterborne 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. Botulism cannot be caught from an infected person.

• Food borne botulism - occurs when the spores of Clostridium botulinum have germinated in a foodstuff and the bacteria then grow and produce toxin. The toxin is consumed when the food is eaten. Clostridium 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 – this is extremely rare; only 3 cases are known to ever have occurred.

A deliberate release of botulinum toxin would most likely be via the airborne or contamination of foodstuffs route.

• Intestinal colonisation botulism - usually occurs in infants 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.
  
• Intestinal and wound botulism would be unlikely following a deliberate release of toxin.

How long can you have the infection before developing symptoms?

Between 2 hours and 8 days may elapse between exposure to the toxin in a contaminated food and the development of symptoms, depending on the type and dose of toxin ingested.

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 go on to problems with vision, and 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 prevented or 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. There is no effective vaccine.

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.