Botulism is caused by the bacteria clostridium botulinum, which is found in:
- soil
- dust
- agricultural products, such as honey, beans and corn
The bacteria themselves are not harmful but, if they enter your body, they can begin to produce highly poisonous toxins.
Clostridium botulinum
The clostridium botulinum toxin is the deadliest naturally occurring poison in the world. Just 500g (1.1lb) is enough to kill every human being on the planet.
Clostridium botulinum can produce seven different types of toxin, which are classified as types A through to G. Types A, B, E and F are poisonous to humans. Type F is the most toxic. It is 60 times more poisonous than type B, which is the least toxic.
The toxins produced by clostridium botulinum block a special type of chemical called a neurotransmitter. Neurotransmitters send messages from your brain to the rest of your nervous system (your nerves and spinal cord).
In the case of botulism, the toxin blocks the effects of a neurotransmitter called acetylcholine, which is used by your body to help stimulate muscles. If acetylcholine is blocked, it causes paralysis which, if left untreated, can lead to death.
Food-borne botulism
Food-borne botulism can occur when food becomes contaminated with infected soil. If the food is not properly canned, preserved or cooked, bacteria in the food can start to produce toxins, which are highly poisonous if eaten.
Modern food production techniques use high-temperature processes that ensure that all bacteria are killed. Therefore, cases of food botulism are virtually unheard of in the UK.
Since an outbreak of food-borne botulism in 1989, where contaminated hazelnut yoghurt affected 27 people, there have been another six cases of food-born botulism in the UK up to 2006. All of these were caused by eating homemade food that was prepared in other countries.
Wound botulism
Wound botulism occurs when a wound becomes infected with the clostridium botulinum bacteria. This is caused by injecting or sniffing drugs that are contaminated with the bacteria. Once inside your body, the bacteria produce the poisonous toxins.
In England and Wales, wound botulism used to be very rare with no recorded cases before the year 2000.
But from 2000 to 2007, there were 130 cases of wound botulism in England and Wales. All of these occurred in people who were injecting heroin into their muscles. Most heroin users inject the drug into their veins (intravenously), but some users prefer to inject into the muscles. This may be because:
- they are trying to disguise the signs of heroin injection ('track marks'), or
- their veins have been damaged by previous heroin abuse
Injecting heroin directly into the muscles is very dangerous because it causes tissue damage, which can lead to infection.
It should be stressed that using clean needles or avoiding sharing needles will not prevent wound botulism because it is not the needle that is infected, but the heroin itself.
Most heroin in the UK comes from opium poppies that are grown in Asia or the Middle East, particularly Afghanistan. The opium is cooked, and the morphine is extracted before being treated with chemicals to produce heroin. The drugs are then often 'cut' with bulking materials, such as starch and lactose. The heroin can become contaminated at any point during this process.
Some cases of wound botulism have also been linked to nasal tissue damage caused by snorting cocaine. The damaged tissue can then become infected. However, no cases of this kind have ever been recorded in the UK.
Infant botulism
Infant botulism occurs when a baby ingests spores of the clostridium botulinum bacteria. The spores make their way to the intestine (part of the digestive system) where they begin to produce toxins.
Clostridium botulinum bacteria spores are harmless to older children and adults. This is because after about one year of age you develop defences that counter the effects of the spores.
Honey and corn syrup have been known to cause some cases of infant botulism, although no definitive cause was found in the majority of cases. There have been eight cases of infant botulism in England and Wales between 1978 and 2007.
Alternative causes
It is possible to be infected with the botulinum toxin in other ways, although these have never happened in the UK. Possibilities include:
- an incorrect injection during botox – this is a beauty treatment that uses the toxin to temporarily paralyse the facial muscles in order to reduce wrinkles
- inhaling (breathing in) the toxin when it is in the form of a gas – this would need to be deliberately prepared, for example, by terrorists
- drinking the toxins in water – the normal treatment of water in the mains water supply would deactivate the toxins, so this would need to be contaminated deliberately, for example, by terrorists
