Most people know that botulism is dangerous, but many are confused about whether it's an infection or a case of poisoning. In fact, it can be both. Clostridium botulinum is a worldwide bacterium that inhabits rivers, soil, and the guts of mammals, fish, and shellfish. It's not an organism that normally makes its living by attacking humans. We most often encounter C. botulinum by accident.
C. botulinum secretes a neurotoxin (nerve poison) that can weaken or paralyze muscles and can even cause death. This is botulin toxin, one of the most dangerous substances known. Botulism is the condition of having been poisoned with C. botulinum toxin.
Botulism is rare, but there are still cases every year.
There are four ways to get botulism:
- Foodborne botulism occurs when food contaminated with the toxin is eaten. The bacteria are dead or gone by the time you eat the food, but the toxin remains. Most foodborne botulism is attributed to home-canned foods, but outbreaks occasionally occur in commercially-prepared foods.
- Infant botulism occurs when infants under 6 months of age eat bacterial spores rather than the toxins. Spores of C. botulinum then grow in the infant's intestines, where they produce toxins. Honey can contain spores of C. botulinum and is associated with infant botulism and should not be given to children under 6 months old. Infant botulism is rare.
- Adult intestinal colonization botulism occurswhen C. botulinum spores are ingested. The spores grow and eventually produce toxins in the digestive system. People with altered gastrointestinal systems and local microbes (due to surgery, presence of inflammatory bowel disease, or exposure to antibiotics) are most often affected.
- Wound botulism occurs when live bacteria infect an open cut and the toxin is carried through the body by the blood.
Rarely, toxins can be inhaled or absorbed through the eyes.
Ironically, some people intentionally get localized botulism from their doctor these days. The toxin is used to make a medication that is injected into twitching and spasmodic muscles to temporarily paralyze them. It's a treatment used for a variety of nerve disorders and for the cosmetic purpose of removing frown lines, forehead wrinkles, and "crow's feet" around the eyes.
Botulism can cause death due to paralysis of muscles used in breathing. However, advancements in supportive care have greatly reduced the death rate, and now less than 10% of people who get botulism die from the condition.
Symptoms and Complications
C. botulinum toxin attacks nerve endings, damaging them and then stopping muscle function. It can't cross the barrier that protects the brain. The heart has its own wiring system and also isn't affected. However, botulin can affect all the other nerves of the body, including the nerves of the muscles that operate the lungs. Botulin toxin kills by shutting down breathing.
Symptoms usually appear quickly in foodborne botulism, within 12 to 36 hours, but a few people feel no symptoms for as many as 8 days after eating the poison. Dry mouth, vomiting, nausea, diarrhea, and abdominal cramps are the first signals. Then the neurological symptoms begin to appear – the muscles slowly shut down, starting with the temple and forehead and proceeding slowly down both sides of the body. The face goes slack and expressionless, the eyelids droop, and the victim may drool. Vertigo and double vision are common. The arms slowly get weaker, then the legs. Diarrhea is replaced by constipation. By this time there's also difficulty in talking, swallowing, and breathing. Temperature and pulse remain normal.
The first sign of infant botulism is constipation. The neurological symptoms are the same as in foodborne botulism but develop less rapidly. This is because the spores produce toxin slowly and the child absorbs it bit by bit instead of all at once as in foodborne botulism. The baby may also suck milk weakly, have difficulty crying loudly, lose head control, and lack facial expression.
Making the Diagnosis
Your doctor will ask you questions about your symptoms and perform a physical exam.
The Botulism Reference Service for Canada conducts the laboratory investigation for diagnosing botulism. The diagnosis of foodborne botulism is made by verifying whether the botulin toxin is in the food. Alternatively, C. botulinum can be isolated from the stool or stomach fluids. The diagnosis of intestinal botulism is made by identifying C.botulinum organisms and toxin in the feces. The diagnosis of wound botulism is made by detecting the toxin in the wound or by isolating C.botulinum from a positive wound culture.
Treatment and Prevention
Supportive care is provided to anyone with botulism. This may include hospitalization, use of a ventilator to help with breathing, and nursing care. Recovery can take many weeks as paralysis slowly improves.
While there is a botulism antitoxin and immune globin therapy, they are not approved for sale in Canada and are currently only available through Health Canada’s Special Access Program.
The antitoxin works by neutralizing botulin. However, the antitoxin needs to be administered as soon as possible after diagnosis. The medication can't repair nerve endings already damaged. This means that while you may survive, you will be temporarily left in the state you were in at the time the medication was administered. That may mean paralysis, sometimes to the point of being unable to talk or even swallow.
The good news is that you'll recover, because new nerves can grow to replace those that were killed. However, this is a slow recovery process and it may take weeks or months, even up to a year, for this to occur.
The antitoxin is generally not given for infant botulism.
For wound botulism, antibiotics are given in addition to supportive care.
Preventing botulism is usually possible. However, if you prepare and store a lot of your own food, you may be creating unnecessary risk. The C. botulinum bacterium is anaerobic, meaning it likes airless environments. This is why you can get foodborne botulism out of a can. Very few cases of botulism arise from commercially canned food. Most occur when individuals can their own products.
Botulin toxin has been found in North America in these foods:
- baked potatoes
- canned corn
- chicken, chicken livers, and liver paté
- garlic-in-oil dressing
- green beans
- luncheon meats
- ripe olives
- smoked and salted fish
- stuffed eggplant
- tuna fish
Only highly acidic foods are safe from C. botulinum. Freezing will shut down toxin production, but a fridge isn't cold enough. The following food handling procedures can help you to prevent foodborne botulism:
- Preserved food should be heated to a temperature above 100°C (212°F) for at least 10 minutes during the canning process.
- Cook food at 79.9°C (176°F) for at least 30 minutes. This usually destroys toxins.
- Do not eat or store cooked foods that have been at room temperature for 4 hours or more.
- Do not eat foil-wrapped baked potatoes that have been left at room temperature, and do not store chopped garlic or onions in oil at room temperature.
- If eating home-canned food, boil it first with frequent stirring for 10 minutes.
- Do not feed honey to infants less than 6 months old.