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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 California.
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-Barré 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 street drugs.
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.
For information and guidelines on canning foods at home:
USDA Home Canning Guide
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