Botulism is a rare but serious illness that is caused by toxins (poisons) produced by specific bacteria. In severe cases, botulism can lead to paralysis or death.
The cause of botulism is a nerve toxin (botulinum toxin) that is produced by the bacterium Clostridium botulinum.
Clostridium botulinum is the name of a group of bacteria commonly found in soil and marine sediments worldwide; their spores are often found on the surfaces of fruits and vegetables and in seafood. These rod-shaped organisms grow best in low-oxygen conditions. The bacteria form spores that allow them to survive in a dormant state until exposed to conditions that can support their growth.
The bacteria and spores themselves are harmless; the dangerous substance is the toxin produced by the bacteria when they grow.
What Are Botulinum Toxins?
Botulism bacteria produce seven types of botulinum toxin, designated by the letters A through G; only types A, B, E, and F cause botulism in humans. Botulinum toxin is one of the most poisonous substances known to exist.
Botulinum toxins affect people of all ages by preventing certain nerves from functioning, resulting in muscle paralysis. Because of this action, these toxins are designated "neurotoxins."
Botulinum toxins, however, do have beneficial uses. Doctors use them to treat certain human diseases caused by muscle problems, such as strabismus (crossed eyes). It is also used to eliminate facial wrinkles.
There are three main kinds of botulism, distinguished by the manner in which they are contracted:
A fourth type of botulism is bioterror botulism.
The foodborne type is caused by eating foods that contain the botulism toxin. Wound botulism is caused by toxin produced from a wound infected with
Clostridium botulinum. Infant botulism is caused by consuming the spores of the botulinum bacteria, which then grow in the intestines and release toxin. A number of infant botulism cases have been associated with eating honey contaminated with
C. botulinum spores
(see Botulism in Honey).
All forms of the illness can be fatal and are considered medical emergencies. Foodborne botulism can be especially dangerous because many people can be poisoned by eating contaminated food.
The time between a person becoming infected with botulism bacteria and the beginning of symptoms is called the "botulism incubation period." The incubation period varies based on the type. For foodborne botulism, the incubation period is between 18 to 36 hours, but can occur as early as 6 hours or as late as 10 days.
The incubation period for infant botulism is between 3 and 30 days, while the incubation period for wound botulism is around 10 days.
The earliest symptoms may include:
- Double vision
- Drooping eyelids
- Slurred speech
- Dry mouth
- Blurred vision
- Difficulty swallowing
- Muscle weakness.
Infants with early symptoms of botulism may:
If a healthcare provider cannot identify and treat the illness early, the symptoms progress to paralysis of the:
- Arms
- Legs
- Trunk
- Respiratory system.
People with respiratory symptoms may have to use a ventilator to help them breathe until they recover from the toxin, which normally requires 2 to 8 weeks.
In order to make a diagnosis, the doctor will ask a number of questions and perform a physical exam looking for signs of the toxin. If the doctor suspects botulism, he or she will send a blood or stool sample to a specialized laboratory for analysis.
Because botulism occurs rarely and the symptoms are similar to those seen in other diseases, diagnosis is difficult and the condition is frequently misdiagnosed.
Other diseases that can appear similar to botulism include:
(Click Botulism Diagnosis for more information.)
Treatment of this illness includes:
- Careful observation
- Supportive care
- Administering a botulism antitoxin.
Antibiotics are of little use to treat the symptoms caused by the toxin, but healthcare providers use them to treat wound botulism. Currently, there is no vaccine approved by the U.S. Food and Drug Administration (FDA) for use on botulism. Research on a vaccine, however, is at an advanced stage.
Botulism can result in death due to respiratory failure. However, in the past 50 years, the proportion of patients with botulism who die has fallen from about 50 percent to 8 percent. A patient with a severe case may require a breathing machine as well as intensive medical and nursing care for several months. Patients who survive an episode of botulism poisoning may have fatigue and shortness of breath for years, and long-term treatment may be needed to aid recovery.
In the United States, an average of 110 cases of botulism are reported each year. Of these, approximately:
- 25 percent are foodborne botulism
- 72 percent are infant botulism
- 3 percent are wound botulism.
The number of cases of foodborne and infant botulism has changed little in recent years, but wound botulism has increased because of the use of black-tar heroin, especially in California.
