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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.
Clostridium botulinumClostridium
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.
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.
Diagnosing botulism
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.
Preventing botulism 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.
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