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What is botulism?
Botulism is a rare but serious paralytic illness caused by a nerve toxin that
is produced by the bacterium Clostridium botulinum. There are three main kinds of
botulism. Foodborne botulism 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.
All forms of botulism can be fatal and are considered medical emergencies.
Foodborne botulism can be especially dangerous because many people can be poisoned
by eating a contaminated food.
What kind of germ is Clostridium botulinum?
Clostridium botulinum is the name of a group of bacteria commonly found in soil.
These rod-shaped organisms grow best in low oxygen conditions. The bacteria form
spores which allow them to survive in a dormant state until exposed to conditions
that can support their growth. There are seven types of botulism toxin designated
by the letters A through G; only types A, B, E and F cause illness in humans.
How common is botulism?
In the United States an average of 110 cases of botulism are reported each year.
Of these, approximately 25% are foodborne, 72% are infant botulism, and the rest are
wound botulism. Outbreaks of foodborne botulism involving two or more persons occur
most years and usually caused by eating contaminated home-canned foods. 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
What are the symptoms of botulism?
The classic symptoms of botulism include double vision, blurred vision, drooping
eyelids, slurred speech, difficulty swallowing, dry mouth, and muscle weakness.
Infants with botulism appear lethargic, feed poorly, are constipated, and have a
weak cry and poor muscle tone. These are all symptoms of the muscle paralysis caused
by the bacterial toxin. If untreated, these symptoms may progress to cause paralysis
of the arms, legs, trunk and respiratory muscles. In foodborne botulism, symptoms
generally begin 18 to 36 hours after eating a contaminated food, but they can occur
as early as 6 hours or as late as 10 days.
How is botulism diagnosed?
Physicians may consider the diagnosis if the patient's history and physical
examination suggest botulism. However, these clues are usually not enough to allow
a diagnosis of botulism. Other diseases such as Guillain-Barr? syndrome, stroke,
and myasthenia gravis can appear similar to botulism, and special tests may be
needed to exclude these other conditions. These tests may include a brain scan,
spinal fluid examination, nerve conduction test (electromyography, or EMG), and a
tensilon test for myasthenia gravis. The most direct way to confirm the diagnosis
is to demonstrate the botulinum toxin in the patient's serum or stool by injecting
serum or stool into mice and looking for signs of botulism. The bacteria can also
be isolated from the stool of persons with foodborne and infant botulism. These
tests can be performed at some state health department laboratories and at CDC.
How can botulism be treated?
The respiratory failure and paralysis that occur with severe botulism may
require a patient to be on a breathing machine (ventilator) for weeks, plus
intensive medical and nursing care. After several weeks, the paralysis slowly
improves. If diagnosed early, foodborne and wound botulism can be treated with an
antitoxin which blocks the action of toxin circulating in the blood. This can
prevent patients from worsening, but recovery still takes many weeks. Physicians
may try to remove contaminated food still in the gut by inducing vomiting or by
using enemas. Wounds should be treated, usually surgically, to remove the source
of the toxin-producing bacteria. Good supportive care in a hospital is the
mainstay of therapy for all forms of botulism. Currently, antitoxin is not
routinely given for treatment of infant botulism.
Are there complications from botulism?
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% to 8%. A patient with severe botulism 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 therapy may be needed to aid recovery.
How can botulism be prevented?
Botulism can be prevented. Foodborne botulism has often been from home-canned
foods with low acid content, such as asparagus, green beans, beets and corn.
However, outbreaks of botulism from more unusual sources such as chopped garlic
in oil, chile peppers, tomatoes, improperly handled baked potatoes wrapped in
aluminum foil, and home-canned or fermented fish. Persons who do home canning
should follow strict hygienic procedures to reduce contamination of foods. Oils
infused with garlic or herbs should be refrigerated. Potatoes which have been
baked while wrapped in aluminum foil should be kept hot until served or
refrigerated. Because the botulism toxin is destroyed by high temperatures,
persons who eat home-canned foods should consider boiling the food for 10 minutes
before eating it to ensure safety. Instructions on safe home canning can be obtained
from county extension services or from the US Department of Agriculture. Because
honey can contain spores of Clostridium botulinum and this has been a source of
infection for infants, children less than 12 months old should not be fed honey.
Honey is safe for persons 1 year of age and older. Wound botulism can be prevented
by promptly seeking medical care for infected wounds and by not using injectable
What are public health agencies doing to prevent or control botulism?
Public education about botulism prevention is an ongoing activity. Information
about safe canning is widely available for consumers. State health departments
and CDC have persons knowledgeable about botulism available to consult with
physicians 24 hours a day. If antitoxin is needed to treat a patient, it can be
quickly delivered to a physician anywhere in the country. Suspected outbreaks of
botulism are quickly investigated, and if they involve a commercial product,
the appropriate control measures are coordinated among public health and
regulatory agencies. Physicians should report suspected cases of botulism
to a state health department.
information and quidelines on canning foods at home.
Source: Coordinating Center for Infectious Diseases/Division of Bacterial
and Mycotic Diseases - October 6, 2005.
Adapted by Editorial Staff, August 2007
Last update, August 2008