Botulism

Clostridium botulinum bacteria form dormant cells called spores. These dormant spores are present widely in the environment including in soil and in river and sea water. Like seeds, spores can exist in a dormant state for many years and they are highly resistant to destruction, for example, by heat. When moisture and nutrients are present and oxygen is absent (as in the intestine or in sealed jars or cans), the spores develop into active bacteria and produce toxins. Some toxins produced by Clostridium botulinum are not destroyed by stomach acid or the intestine’s protective enzymes.

Clostridium botulinum is common in the environment, and spores can be transported by air. Occasionally, cases of botulism result from ingesting or inhaling small amounts of soil or dust that contain spores. Also, the toxin can be used as a weapon. Spores can also enter the body through the eyes or a break in the skin.

However, most cases result from eating food that contains the toxins.

There are different forms of botulism, which have different causes. The most common forms are

• Foodborne botulism

• Wound botulism

• Infant botulism (discussed elsewhere)

A rare form of botulism is called intestinal toxemia botulism. It can occur if the spores get into a person's intestines and produce the toxin there. When intestinal toxemia botulism occurs in infants, it is called infant botulism. In children 1 year of age and older and in adults, the botulism is called adult intestinal toxemia botulism. These two types of intestinal toxemia botulism differ from foodborne botulism, which is more common and occurs when people ingest food contaminated with the toxin itself. It is not clear how spores get into the intestine in intestinal toxemia botulism. In infants, swallowing honey or being around contaminated soil may be the source. In adults, those who have had surgery on their stomach or intestines, have inflammatory bowel disease, or have been on antibiotics have a greater risk of developing intestinal toxemia botulism.

The various forms of botulism cause many of the same symptoms:

• Dry mouth

• Blurred or double vision

• Drooping eyelids

• Difficulty focusing on nearby objects

• Pupils that do not constrict normally when exposed to light

• Slurred speech

• Difficulty swallowing

Nerve damage by the toxins affects muscle strength but not sensation. The mind usually remains clear.

Because swallowing is difficult, food or saliva may be inhaled (aspirated) into the lungs, causing choking or gagging and increasing the risk of pneumonia (called aspiration pneumonia).

Typically, after strength is lost in the muscles of the face and head, strength is then gradually lost in the muscles of the arms and legs and in the muscles involved in breathing. Muscles become progressively weaker. Paralysis of breathing muscles can cause death if mechanical ventilation (use of a machine to assist breathing) is not provided.

In foodborne botulism, symptoms develop suddenly, usually 18 to 36 hours after toxins enter the body, although symptoms can start as soon as 4 hours or as late as 8 days after ingesting the toxins. The more toxin ingested, the sooner people become sick.

The first symptoms of foodborne botulism are often nausea, vomiting, stomach cramps, and diarrhea. Over time, many people become constipated. These digestive symptoms usually occur before muscles are affected.

People with wound botulism do not have digestive symptoms.

• When possible, tests to detect toxins in food, blood, or stool

• Sometimes electromyography

Doctors suspect botulism based on symptoms. However, other disorders can cause similar symptoms, so additional information is needed.

For foodborne botulism, a likely food source provides a clue. For example, when botulism occurs in two or more people who ate the same food prepared in the same place, the diagnosis is clearer. The diagnosis is confirmed when the toxins are detected in the blood or when the bacteria or toxins are detected in a sample of stool. Toxins may also be identified in food that was eaten.

For wound botulism, doctors ask whether people have had an injury that broke the skin. Doctors may inspect the skin for puncture marks suggesting use of an illicit drug. The diagnosis is confirmed when the toxins are detected in the blood or when the bacteria are detected in a culture of tissue from the wound.

Electromyography (electrical stimulation of muscles and recording of their electrical activity) may be useful. In most cases of botulism, electromyography shows abnormal muscle responses after electrical stimulation.

Sometimes determining whether botulism developed from a wound or from food is impossible.

• Sometimes activated charcoal to prevent absorption of toxin consumed in food

• Antitoxin

• For breathing problems, use of a mechanical ventilator

If people think they may have botulism, they should go to the hospital immediately. If botulism is diagnosed, they are hospitalized and closely monitored.

Laboratory tests to confirm the diagnosis may be done, but treatment cannot be delayed until the results are known. To help eliminate any unabsorbed toxin, doctors may give activated charcoal by mouth or through a tube passed through the nose or mouth and into the stomach.

Vital signs (pulse, breathing rate, blood pressure, and temperature) are measured often. If breathing problems begin, people are transferred to an intensive care unit and may be temporarily placed on a mechanical ventilator. Such treatment has reduced the percentage of deaths due to botulism to less than 10% currently.

If needed, people who cannot swallow can be fed through a thin plastic feeding tube (a nasogastric tube) inserted through the nose and down the throat.

Some people who recover from botulism feel tired and are short of breath for years afterward. They may need long-term physical therapy.

People do not develop immunity to Clostridium botulinum toxin after an infection, so they can become infected again.

• Thorough cooking or heating of food

• Appropriate storage and handling of food

The spores of Clostridium botulinum are highly resistant to heat and may survive boiling for several hours. However, the toxins are readily destroyed by heat.

Stored foods can cause botulism if they were inadequately cooked before they were stored. The bacteria can produce some toxins at temperatures as low as 37.4° F (3° C), a typical refrigerator temperature, so refrigerating food does not automatically make it safe.

The following measures can help prevent foodborne botulism:

• Cooking food at 176° F (79.9° C) for 30 minutes, which almost always destroys toxins

• Discarding canned foods that are discolored or smell spoiled or are swollen or leaking

• Following the home-canning instructions from the Centers for Disease Control and Prevention (CDC)

• Keeping potatoes that have been baked in aluminum foil hot until served

If people are unsure whether a can should be discarded, they can check it when they start to open it. Before making the first puncture, they can place a few drops of water in the spot to be punctured. If water is expelled rather than sucked into the can when the can is punctured, the can is contaminated and should be discarded. If there is any question whether a can of food is safe, it is better to discard it than risk getting botulism.

Any food that may be contaminated should be disposed of carefully. Even tiny amounts of toxins ingested, inhaled, or absorbed through the eye or a break in the skin can cause serious illness. Skin contact should be avoided as much as possible, and hands should be washed immediately after handling the food.

If a wound becomes infected, promptly seeking medical attention can reduce the risk of wound botulism.

The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

1. Centers for Disease Control and Prevention (CDC): Home-canning instructions for preventing botulism and information about how to recognize contaminated food and how to properly dispose of it

2. Infant Botulism Treatment and Prevention Program: Web site or call 510-231-7600: Provides information about treatment, prevention, and support groups