Botulism is a rare but potentially fatal condition caused by toxins produced by Clostridium botulinum bacteria.
The toxins produced by C. botulinum are some of the most powerful toxins known to science. They attack the nervous system (nerves, brain and spinal cord) and cause paralysis (muscle weakness) that gradually spreads down the body from the head to the legs.
Other symptoms of botulism can include:
- blurred or double vision
- drooping eyelids
- difficulty swallowing (dysphagia)
- difficulty speaking (dysarthria)
If the condition is not treated quickly, the paralysis will eventually affect the muscles controlling breathing. This can cause fatal respiratory failure in up to one in every 10 people with the condition.
Botulism is a serious condition requiring immediate medical attention. Dial 999 for an ambulance if you or someone you know has symptoms of botulism.
Read more about the symptoms of botulism.
What causes botulism?
Botulism is caused by the bacteria Clostridium botulinum, found in soil, dust and river or sea sediments. The bacteria themselves are not harmful, but they can produce highly poisonous toxins when they are deprived of oxygen (such as in closed cans or bottles, stagnant soil or mud, or occasionally the human body).
There are three main types of botulism, which have slightly different causes:
- food-borne botulism can occur when someone eats food that is contaminated with infected soil if the food has not been properly canned, preserved or cooked
- wound botulism can occur when a wound becomes infected with the C. botulinum bacteria, it is usually caused by injecting illegal drugs contaminated with the bacteria, such as heroin, into muscle rather than a vein
- infant botulism can occur when a baby ingests spores of the C. botulinum bacteria in contaminated soil or food, such as honey
All these types of botulism are rare in the UK, although wound botulism has been by far the most common in the last 15 years or so.
In England and Wales since 2000, there have been 147 cases of wound botulism (eight deaths), but only seven cases of food-borne botulism (one death) and 11 cases of infant botulism (no deaths).
Read more about the causes of botulism.
Identifying and treating botulism
As botulism is a potentially life-threatening condition, it is usually diagnosed following admission to hospital.
A diagnosis is mainly based on your symptoms, although tests will be carried out on a sample of blood, faeces (stool), stomach contents, food, pus or tissue to detect the C. botulinum bacteria or toxin in order to confirm the diagnosis.
However, as treatment is most effective when given quickly, it will usually begin before the test results come back.
The way in which the condition is treated depends on the type of botulism you have, but treatment will usually involve neutralising the toxins with injections of special antibodies while the functions of the body (such as breathing) are supported.
Treatment will not reverse paralysis already caused by the toxin, but in most people any paralysis will improve naturally over the following weeks or months.
Read more about how botulism is treated.
Due to high standards of food hygiene in the UK, the chances of getting food-borne botulism from food bought in this country are virtually nil.
There is a slightly higher risk if you produce your own food, particularly if this involves canning. However, following food hygiene procedures and canning recommendations will reduce any risk.
You should also avoid eating food from visibly bulging or damaged cans, foul-smelling preserved foods, foods stored at the incorrect temperature and out of date foods.
Heroin users should avoid injecting heroin into their muscles. Injecting heroin into a vein or smoking can reduce the risk of botulism, although not using heroin at all is by far the best course of action. Read more about getting help to stop using heroin.
The specific cause is not identified in many cases of infant botulism, so it may not always be possible to prevent it. However, you should avoid giving honey to babies less than 12 months old because it has been known to contain C. botulinum spores.
Symptoms of botulism
Botulism is a serious condition that requires immediate medical attention. Dial 999 for an ambulance if you suspect that you or someone you know has symptoms of botulism.
Food-borne and wound botulism
In food-borne botulism, it usually takes 12 to 36 hours for symptoms to develop after eating contaminated food, although it can take as little as six hours or as long as eight days. Occasionally, the first signs may be gastrointestinal symptoms such as nausea, vomiting, diarrhoea and stomach cramps.
Wound botulism most often occurs as a result of injecting illegal drugs and, since most of those affected inject drugs several times a day, it’s difficult to determine how long it takes for symptoms to develop. In some cases, the area around the infected wound may become inflamed (red and swollen).
In both of these types of botulism, any initial symptoms will eventually be followed a few hours or days later by more serious neurological symptoms (symptoms that affect the nervous system).
Neurological symptoms develop as the toxins released by the Clostridium botulinum bacteria begin to spread throughout the body. The toxins affect the nerves in the skull at first but, without treatment, will spread to the nerves controlling the arms, legs and breathing muscles.
In both food-borne and wound botulism, neurological symptoms can include:
- vision problems, such as blurred vision, double vision and drooping eyelids
- difficulty swallowing (dysphagia) and a dry mouth
- difficulty speaking (dysarthria), such as having slurred speech
- facial weakness initially, followed by paralysis that gradually spreads further down the body to the arms, chest and legs
- breathing difficulties, which may eventually lead to respiratory failure and even death
Unlike many other types of severe infection, your awareness of the world around you will not normally be affected and you won’t usually have a high temperature (fever).
The symptoms of infant botulism are also caused by the toxins affecting the nervous system, but they can be slightly different to those of food-borne or wound botulism.
The first sign of infant botulism is usually constipation. This may last for several days before the baby starts to have neurological symptoms such as:
- a weak cry
- an inability to suck, making feeding difficult
- increased drooling
- droopy eyelids
- a floppy head, neck and limbs (hypotonia)
Causes of botulism
Botulism is caused by Clostridium botulinum bacteria, which can be found in soil, dust and river or sea sediments.
The bacterium itself is not harmful, but it can produce highly poisonous toxins when deprived of oxygen (such as in closed cans or bottles, stagnant soil or mud, or occasionally the human body). These toxins are some of the deadliest substances known to science.
C. 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, with Type F the most toxic and type B the least toxic.
These toxins stop nerve cells releasing a chemical called acetylcholine, which is needed for signals to be sent from your nerves to your muscles. This lack of acetylcholine can cause paralysis that gets gradually worse and, if left untreated, can be fatal.
Botulism is usually divided into three main types, depending on the way the bacteria get into the body. These are described below.
Food-borne botulism can occur when food becomes contaminated with infected soil. If food is not properly canned, preserved or cooked, any C. botulinum bacteria in the food can start producing toxins that are highly poisonous if eaten.
Modern food production techniques use high-temperature processes that ensure all bacteria are killed. Therefore, cases of food botulism are virtually unheard of in the UK.
However, faults during the food processing or storage process can lead to very occasional outbreaks and there is a risk of homemade food becoming contaminated if proper storage and cooking precautions are not taken.
Following an outbreak of food-borne botulism in 1989, where contaminated hazelnut yoghurt affected 26 people and resulted in one death, there have been another nine cases of this type of botulism in England and Wales up to 2013. All nine cases were caused by eating homemade food or food produced in other countries.
Wound botulism occurs when a wound becomes infected with the C. botulinum bacteria. Most cases are caused by injecting or sniffing drugs contaminated with the bacteria. Once inside your body, the bacteria can produce the poisonous toxins.
From 2000 to 2013 there were 147 cases of wound botulism in people who inject drugs in England and Wales. All of these occurred in people injecting heroin into their muscles.
Most heroin users inject the drug into their veins, but some users prefer to inject into muscles. This may be because they are trying to disguise signs of heroin injection (“track marks”) or their veins have been damaged by previous heroin abuse.
Injecting heroin directly into muscle increases the risk of botulism because it provides a better environment for the C. botulinum to produce toxins. Even very small infections can cause severe illness, as the bacteria continuously produce toxins that build up to high levels.
Using clean needles and not sharing needles with others 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 grown in Asia or the Middle East, particularly Afghanistan. The opium is cooked and the morphine extracted before being treated with chemicals to produce heroin. The drugs are then ‘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 become infected. However, no cases of this kind have ever been recorded in the UK.
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. After about the age of one year the baby develops defences that counter the effects of the spores.
Honey and corn syrup have been known to cause some cases of infant botulism, although some cases have been linked to ingesting contaminated soil or dust. No definitive cause is found in many cases.
There were only 16 cases of infant botulism in England and Wales between 1975 and 2013, although 10 of these occurred from 2007 onwards. None of the 16 cases were fatal.
Other possible 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 of botulinum toxin – botulinum toxin injections (such as Botox) can be used to make wrinkles less obvious, however there have been a few cases where a version of the medication that was not intended for human use caused botulism
- breathing in the toxin when it is in the form of a gas – this does not happen naturally and would need to be deliberately prepared, for example by terrorists
- drinking the toxins in water – the normal treatment process for mains water supply would de-activate the toxins, so the water would need to be deliberately contaminated, for example by terrorists
Botulinum toxins cannot be spread from person to person.
Treatment for botulism will depend on the type of botulism you have, although in all cases you will need to be admitted to hospital.
If botulism is not treated quickly, it is likely to be fatal. With treatment, it is usually possible to stop the toxins causing further paralysis (muscle weakness), although it can take weeks or even months to fully recover.
Food-borne and wound botulism
Treatment for food-borne and wound botulism in hospital will involve supporting the body’s functions while specific treatments are carried out.
If you are having difficulty breathing because the toxin is affecting the muscles used for breathing, you may be attached to a mechanical ventilator (a machine that helps you breathe by moving oxygen-enriched air in and out of your lungs).
You may also be given fluids and nutrients through an intravenous drip (where a tube is placed directly into a vein in your arm).
Both food-borne and wound botulism will also need to be treated with injections of antitoxins. These are special antibodies (proteins produced by the body) that can block the effects of the Clostridium botulinum toxin on the nervous system (the nerves, brain and spinal cord).
Antitoxins should be given as soon as possible, even before test results have confirmed Clostridium toxin as the cause of the symptoms. A diagnosis of botulism based on your symptoms is enough to begin treatment.
The antitoxin will help prevent your symptoms from getting worse but it will not reverse the paralysis already caused. But this will improve naturally over the following weeks or months in most people.
If one dose of antitoxin is not enough, you may be given a second dose after 24 hours.
Treating or removing the source of infection
In some cases of food-borne botulism, medication may be used to induce vomiting or help you empty your bowel to remove the contaminated food from your body.
If you have wound botulism, the infected wound and possibly a surrounding area of tissue may need to be surgically removed. This is known as debridement and it is often necessary to stop further toxins being produced.
You may also be given antibiotics if you have wound botulism to prevent any further infections developing.
Infant botulism tends to be less serious than other types of botulism because the levels of toxins released by the bacteria are lower than in other forms of the condition. However, the condition still requires emergency medical treatment in hospital to prevent breathing difficulties occurring.
Babies with infant botulism will be placed in an incubator to keep them warm and protect them from other infections. Artificial ventilation may be required to assist their breathing, and they may also be fed intravenously.
Infant botulism can normally be treated effectively using a medicine called botulinum immunoglobulin (also called BabyBIG). Botulinum immunoglobulin is created by extracting the antibodies from human blood that contains a high level of infant botulism-immune antibodies.
Babies with infant botulism usually respond quickly to treatment and are well enough to leave hospital within a few weeks. Any paralysis may last a few weeks, but most babies will make a full recovery.