Farm and Home Biosecurity
Consumer/General Public
Botulism: Questions and Answers
What is botulism?
Botulism
is a muscle-paralyzing disease caused by a toxin made by a bacterium called Clostridium
botulinum. Naturally occurring
botulism is the disease that results from the absorption of the botulism toxin
into the circulation from a mucosal surface (gut, lung) or a wound. It does not penetrate intact skin.
There
are three main kinds of botulism:
Foodborne botulism occurs when a person ingests pre-formed toxin that
leads to illness within a few hours to days. Foodborne botulism is a public
health emergency because the contaminated food may still be available to other
persons besides the patient.
Infant botulism occurs in a small number of susceptible infants each year
who harbor C. botulinum in their intestinal tract.
Wound
botulism occurs when wounds are infected with C. botulinum that secretes
the toxin.
Botulism toxin is the most poisonous substance known. A single gram of crystalline toxin, evenly dispersed and inhaled, would
kill more than a million people, although technical factors would make such
dissemination difficult, if not impossible.
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.
Botulism is not spread from one person to another.
No cases of waterborne botulism have ever been reported.
This is likely due to the large amount of toxin needed, and the fact that
the toxin is easily neutralized by common water treatment techniques.
A supply of antitoxin against botulism is maintained by CDC.
The antitoxin is effective in reducing the severity of symptoms if
administered early in the course of the disease.
Back to Consumer/General Public |
