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What is Botulism
Botulism is a disease caused by the toxins (poisons) produced by several members of the group of bacteria called Clostridium botulinum. These bacteria are found in soil throughout the world and produce spores that are able to survive in a dormant state until more favorable conditions allow them to grow.
The seven distinct toxins they produce are some of the most deadly substances known. The toxins are designated by the letters A through G, and types A, B, E, and F toxins have produced human disease. 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." For more information on the chemical actions of the botulinum toxins, visit our Botox page.
Botulism in humans is most often the result of eating food containing the toxin. Botulinum neurotoxins are also a serious bioterrorism concern because the toxins are relatively easy to make and deliver and are highly lethal. Unlike infectious diseases, however, botulism cannot be transmitted from one person to another.
There are three main kinds of botulism, each transmitted a different way.
Foodborne botulism is caused by eating foods contaminated with botulinum spores that grow into bacteria and produce neurotoxin in the food. A common cause of this illness is improperly preserved home-processed foods with low acid content, such as green beans, beets, and corn. Less likely sources include fish products and other commercially processed foods. The actual number of cases in the United States is small with approximately 9 outbreaks of foodborne botulism per year with and average of 2.4 cases per outbreak.
Wound botulism occurs when C. botulinum spores contaminate a wound, germinate, grow within the wound, and produce toxin that is absorbed into the bloodstream. Wound botulism is associated with crush injuries and with illicit drug use. The increasing number of people who inject black tar heroin from Mexico is a growing concern because this crude drug can contain C. botulinum spores.
Infant botulism occurs when an infant consumes the spores of C. botulinum, which then grow in the baby's intestines and produce toxins. A number of such cases have been associated with eating honey contaminated with C. botulinum spores.
Botulinum toxins, however, do have beneficial uses. Doctors use it to treat certain human diseases caused by muscle problems, such as strabismus (crossed eyes). It is also used to eliminate facial wrinkles. For more information, visit our Botox page.
Symptoms produced by each toxin type are quite similar. The first symptoms of botulism may include
- Double vision
- Blurred vision
- Drooping eyelids
- Slurred speech
- Difficulty swallowing
- Dry mouth
- Muscle weakness
If a health care provider cannot identify and treat the disease early, the symptoms progress to paralysis of the arms, legs, trunk, and 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. Death occurs in 5 to 10 percent of cases of foodborne botulism.
Because botulism occurs rarely and the symptoms are similar to other neurological diseases, diagnosis is difficult and the disease is frequently misdiagnosed. The laboratory test used to confirm a diagnosis of botulism is sensitive and specific but can take up to 4 days to complete and is available in only a few laboratories.
A photomicrograph of Clostridium botulinum bacteria. Image courtesy of the CDC.
Treatment of botulism includes careful observation, supportive care, and administering the antitoxin. The antitoxin will reduce the progression of the paralysis and may reduce the severity and duration of symptoms. Patients may still require weeks to months of supportive care, however, before they fully recover.
Antibiotics are of little use to treat the symptoms caused by the toxin, but health care providers use them to treat wound botulism.
Currently, there is no Food and Drug Administration-approved vaccine for botulism. Research on a vaccine, however, is at an advanced stage. People who work with the toxin (such as laboratory workers) and who are at high risk of exposure can be immunized with botulinum toxoid (a drug that researchers are investigating).
Botulism as an Agent of Bioterrorism
Botulinum toxin has been a concern as a potential biological warfare agent since World War II. In response to concerns about Germany's botulinum toxin research, the United States and Great Britain developed countermeasures against the toxin before the invasion of Europe. More recently, Iraq has been accused of producing large amounts of botulinum toxin for use as a biological warfare agent. The extreme toxicity of botulinum toxins and the ease of production, transport, and delivery make this an agent of extreme bioterrorism concern.
Source: National Institute of Allergy and Infectious Diseases
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