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Botulism is a rare but potentially fatal condition that causes progressive weakness. It is caused by nerve toxins made by the Clostridium botulinum bacterium, found worldwide in soil and sediments. This bacterium can get into the body via cuts, or it can grow and produce potent nerve toxins when foods are not properly cooked, preserved or canned. If untreated, botulism can cause death and is considered a medical emergency.
The toxin that causes this condition is one of the most powerful known poisons. Minute amounts are capable of severely damaging nerves and muscles. The three forms of botulism include intestinal, food-borne and wound botulism. Less than one per cent of babies with intestinal botulism and five to 10 per cent of adults who acquire botulism via contaminated food will die. If a person survives the poisoning, their body will eventually repair the damage. However, recovery may take months.
Symptoms in adults
Symptoms include:
- Dry mouth
- Nausea
- Vomiting
- Swallowing difficulties
- Speaking difficulties
- Visual disturbances, such as double vision
- Increasing weakness and, ultimately, paralysis – progressing from the limbs to the body and finally to the breathing muscles including the diaphragm
- Breathing difficulties.
Symptoms in babies
Symptoms include:
- Constipation
- Poor sucking and feeding
- Choking and gagging
- Weak, feeble cry
- Reduced movements of the limbs
- Inability to control head movements
- Increasing weakness and floppiness
- Paralysis
- Breathing difficulties.
Three forms of botulism
The three forms of botulism include:
- Intestinal botulism – this is the most common form of botulism. Children under the age of 12 months are most susceptible, but adults who have certain gastrointestinal problems may also be at risk. The incubation period for intestinal botulism is not known. The botulism is caused by consuming food, dust or soil that contains Clostridium botulinum spores, which then multiply inside the intestinal tract and produce toxins. Healthy adults aren’t usually affected, because they have natural defences in their gastrointestinal tract that prevents the spores from germinating.
- Food-borne botulism – the toxins are eaten in contaminated food. The symptoms are severe and the poisoning is often fatal. Symptoms generally occur between 12 and 36 hours after eating the contaminated food.
- Wound botulism – this rare form of botulism is caused by contaminated soil or gravel invading a wound. Intravenous drug users are also susceptible. Symptoms occur after four days to two weeks.
Characteristics of Clostridium botulinum
Spores of the Clostridium botulinum bacterium are found worldwide in soil and the sediments of streams, lakes and the sea. They then find their way into agricultural products, animals and fish.
Most human cases of botulism are caused by improperly cooked, preserved or canned foods where growth of the bacterium has produced the toxins. Honey has been implicated as a source of intestinal botulism in the United States, but no Australian honey surveyed has so far contained the bacterium. There are seven different types of Clostridium botulinum, with types A, B, E and F causing human botulism.
The neuromuscular system is affected
For muscular movement to occur, a chemical called acetylcholine must be released from the nerve endings and picked up by special receptors in the muscle tissue. The toxins produced by the Clostridium botulinum bacteria get into the bloodstream and collect in the nerves that service the muscles. They block the release of acetylcholine, triggering the characteristic weakness and paralysis.
A person may have breathing difficulties if the nerves servicing the diaphragm are affected.
Diagnosis methods
Botulism is diagnosed by checking for the presence of the toxin. Various tests may include:
- Blood tests
- Food tests
- Stool culture
- Wound culture
- Electromyogram (to check muscle function).
Treatment options
The most important treatment for botulism is supportive care, including assisted breathing using a ventilator for breathing difficulties and intravenous fluids if the patient can’t swallow. Depending on the type of botulism, additional treatment options may include:
- Purging techniques including induced vomiting, stomach pumping and high enemas after ingestion of spores or toxin
- Drainage of infected wounds
- Antibiotics, such as penicillin, in cases of secondary infection.
Antitoxin against botulism should be administered early, if available, to reduce the severity of the symptoms.
Be careful when preparing home-preserved foods
Botulism has been associated with canned foods and, more recently, with vegetables in oil and some other foods. Take care when preparing home-preserved foods for eating. Discard all raw or canned food that shows any sign of being spoiled.
Don’t taste food from swollen containers or food that is ‘foamy’ or has a bad odour. Don’t rely on smells or ‘blown’ containers alone to signal food contamination, however, as it is not always possible to detect Clostridium botulinum bacterium in this way. When in doubt, throw it out.
Tips for preserving foods at home
When canning or preserving foods at home, pay particular attention to hygiene, cooking time, pressure, temperature, refrigeration and storage. Pressure cooking is the only recommended method for preserving low-acid foods such as meat, poultry, seafood and most vegetables.
Make sure you use the correct equipment, properly sterilise containers and always follow the manufacturers’ instructions for your equipment. Use only recipes with tested proportions of ingredients and be sure to follow recommendations for time, pressure and safe preserving methods appropriate to the size of container, style of pack and kind of food being processed.
Preventing infection in babies
Prevention strategies include:
- Avoid giving honey to babies less than 12 months of age.
- Keep the newborn baby away from soil until the umbilical stump has dropped off and the navel has completely healed.
- Take care when preparing, handling and storing solid foods for baby.
Other precautions
Other ways to reduce the risk of botulism include:
- Wash any wound thoroughly with antibacterial soap and keep clean.
- Avoid injections of illicit drugs.
Where to get help
- Your doctor
- Always call an ambulance in an emergency. Dial triple zero (000)
- Department of Human Services Tel. 1300 651 160 – to report food-borne botulism (this should be done as soon as possible so that the source can be identified and contaminated food recalled)
- Food Science Australia Tel. (02) 9490 8333 – for information on safe home bottling
Things to remember
- Botulism is a rare but potentially fatal condition that causes progressive weakness.
- It is caused by toxins made by the Clostridium botulinum bacterium.
- The bacterium is found in soil, sediments, raw foods (including seafoods) and honey.
- Foods that are not properly cooked, preserved or canned can be the vehicles for human botulism.
- Treatment options include purging techniques, antitoxin medication and supportive care.
You might also be interested in:
Food - 'use-by' and 'best before' dates.
Food labels explained.
Food poisoning - listeria.
Food poisoning - prevention.
Food safety - eggs.
Food safety - storage.
Food safety when cooking.
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