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.
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