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Botulism Français

25 September 2023
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Key facts
Clostridium botulinum is a bacterium that
produces dangerous toxins (botulinum
toxins) under low-oxygen conditions.
Botulinum toxins are one of the most
lethal substances known.
Botulinum toxins block nerve functions
and can lead to respiratory and muscular
paralysis.
Human botulism may refer to foodborne
botulism, infant botulism, wound
botulism, and inhalation botulism or
other types of intoxication.
Foodborne botulism, caused by
 consumption of improperly processed
food, is a rare but potentially fatal
disease if not diagnosed rapidly and
treated with antitoxin.
Homemade canned, preserved or
fermented foodstuffs are a common
source of foodborne botulism and their
preparation requires extra caution.

Overview
Foodborne botulism is a serious, potentially
fatal disease. However, it is relatively rare. It
is an intoxication usually caused by ingestion
of potent neurotoxins, the botulinum toxins,
formed in contaminated foods. Person to
person transmission of botulism does not
occur.

Spores produced by the bacteria Clostridium

botulinum are heat-resistant and exist widely
in the environment, and in the absence of
oxygen they germinate, grow and then
excrete toxins. There are 7 distinct forms of
botulinum toxin, types A–G. Four of these
(types A, B, E and rarely F) cause human
botulism. Types C, D and E cause illness in
other mammals, birds and fish.

Botulinum toxins are ingested through

improperly processed food in which the
bacteria or the spores survive, then grow
and produce the toxins. Though mainly a
foodborne intoxication, human botulism can
foodborne intoxication, human botulism can

also be caused by intestinal infection with C.

botulinum in infants, wound infections, and
by inhalation.

Symptoms of
foodborne botulism
Botulinum toxins are neurotoxic and
therefore a!ect the nervous system.
Foodborne botulism is characterized by
descending, flaccid paralysis that can cause
respiratory failure. Early symptoms include
marked fatigue, weakness and vertigo,
usually followed by blurred vision, dry mouth
and di"culty in swallowing and speaking.
Vomiting, diarrhoea, constipation and
abdominal swelling may also occur. The
disease can progress to weakness in the
neck and arms, after which the respiratory
muscles and muscles of the lower body are
a!ected. There is no fever and no loss of
consciousness.

The symptoms are not caused by the

bacterium itself, but by the toxin produced
by the bacterium. Symptoms usually appear
within 12 to 36 hours (within a minimum and
maximum range of 4 hours to 8 days) after
exposure. Incidence of botulism is low, but
the mortality rate is high if prompt diagnosis
and appropriate, immediate treatment (early
administration of antitoxin and intensive
respiratory care) are not given. The disease
can be fatal in 5 to 10% of cases.

Exposure and
transmission
Foodborne botulism

C. botulinum is an anaerobic bacterium,

meaning it can only grow in the absence of
oxygen. Foodborne botulism occurs when C.
botulinum grows and produces toxins in food
prior to consumption. C. botulinum produces
spores and they exist widely in the
environment including soil, river and sea
water.

The growth of the bacteria and the

formation of toxin occur in products with low
oxygen content and certain combinations of
storage temperature and preservative
parameters. This happens most often in
lightly preserved foods and in inadequately
processed, home-canned or home-bottled
foods.

C. botulinum will not grow in acidic

conditions (pH less than 4.6), and therefore
the toxin will not be formed in acidic foods
(however, a low pH will not degrade any pre-
(however, a low pH will not degrade any pre-
formed toxin). Combinations of low storage

temperature and salt contents and/or pH are

also used to prevent the growth of the
bacteria or the formation of the toxin.

The botulinum toxin has been found in a

variety of foods, including low-acid
preserved vegetables, such as green beans,
spinach, mushrooms, and beets; fish,
including canned tuna, fermented, salted
and smoked fish; and meat products, such
as ham and sausage. The food implicated
di!ers between countries and reflects local
eating habits and food preservation
procedures. Occasionally, commercially
prepared foods are involved.

Though spores of C. botulinum are heat-

resistant, the toxin produced by bacteria
growing out of the spores under anaerobic
conditions is destroyed by boiling (for
example, at internal temperature greater
than 85 °C for 5 minutes or longer).
Therefore, ready-to-eat foods in low oxygen-
packaging are more frequently involved in
cases of foodborne botulism.

Food samples associated with suspect cases

must be obtained immediately, stored in
properly sealed containers, and sent to
laboratories in order to identify the cause
and to prevent further cases.

Infant botulism
Infant botulism

Infant botulism occurs mostly in infants

under 6 months of age. Di!erent from
foodborne botulism caused by ingestion of
pre-formed toxins in food, it occurs when
infants ingest C. botulinum spores, which
germinate into bacteria that colonize in the
gut and release toxins. In most adults and
children older than about 6 months, this
would not happen because natural defences
in intestines that develop over time prevent
germination and growth of the bacterium.

C. botulinum in infants include constipation,

loss of appetite, weakness, an altered cry
and a striking loss of head control. Although
there are several possible sources of
infection for infant botulism, spore-
contaminated honey has been associated
with a number of cases. Parents and
caregivers are therefore warned not to feed
honey to the infants before the age of 1 year.

Wound botulism
Wound botulism is rare and occurs when the
spores get into an open wound and are able
to reproduce in an anaerobic environment.
The symptoms are similar to the foodborne
botulism, but may take up to 2 weeks to
appear. This form of the disease has been
associated with substance abuse,
particularly when injecting black tar heroin.
particularly when injecting black tar heroin.

Inhalation botulism

Inhalation botulism is rare and does not

occur naturally, for example it is associated
with accidental or intentional events (such as
bioterrorism) which result in release of the
toxins in aerosols. Inhalation botulism
exhibits a similar clinical footprint to
foodborne botulism. The median lethal dose
for humans has been estimated at 2
nanograms of botulinum toxin per kilogram
of bodyweight, which is approximately 3
times greater than in foodborne cases.

Following inhalation of the toxin, symptoms

become visible between 1–3 days, with
longer onset times for lower levels of
intoxication. Symptoms proceed in a similar
manner to ingestion of botulinum toxin and
culminate in muscular paralysis and
respiratory failure.

If exposure to the toxin via aerosol

inhalation is suspected, additional exposure
to the patient and others must be prevented.
The patient's clothing must be removed and
stored in plastic bags until it can be washed
thoroughly with soap and water. The patient
should shower and be decontaminated
immediately.

Other types of intoxication

Other types of intoxication

Waterborne botulism could theoretically

result from the ingestion of the pre-formed
toxin. However, as common water treatment
processes (such as boiling, disinfection with
0.1% hypochlorite bleach solution) destroy
the toxin, the risk is considered low.

Botulism of undetermined origin usually

involves adult cases where no food or
wound source can be identified. These cases
are comparable to infant botulism and may
occur when the normal gut flora has been
altered as a result of surgical procedures or
antibiotic therapy.

Adverse e!ects of the pure toxin have been

reported as a result of its medical and/or
cosmetic use in patients, see more on 'Botox'
below.

Botox
The bacterium C. botulinum is the same
bacterium that is used to produce Botox, a
pharmaceutical product predominantly
injected for clinical and cosmetic use. Botox
treatments employ the purified and heavily
diluted botulinum neurotoxin type A.
Treatment is administered in the medical
setting, tailored according to the needs of
the patient and is usually well tolerated
although occasional side e!ects are
observed.

Diagnosis and
treatment
Diagnosis is usually based on clinical history
and clinical examination followed by
laboratory confirmation including
demonstrating the presence of botulinum
toxin in serum, stool or food, or a culture of
C. botulinum from stool, wound or food.
Misdiagnosis of botulism sometimes occurs
as it is often confused with stroke, Guillain-
Barré syndrome, or myasthenia gravis.

Antitoxin should be administered as soon as

possible after a clinical diagnosis. Early
administration is e!ective in reducing
mortality rates. Severe botulism cases
require supportive treatment, especially
mechanical ventilation, which may be
required for weeks or even months.
Antibiotics are not required (except in the
case of wound botulism). A vaccine against
botulism exists but it is rarely used as its
e!ectiveness has not been fully evaluated
and it has demonstrated negative side
e!ects.

Prevention
Prevention of foodborne botulism is based
on good practice in food preparation