Botulism Infection

Botulism is a rare but serious paralytic illness. It is caused by a nerve toxin, botulin. Botulin is produced by the bacterium Clostridium botulinum.

Clostridium botulinum is found in soil and untreated water throughout the world. It produces spores that are able to survive in a dormant state until favourable conditions allow them to grow.

Botulin is the most potent known toxin. It blocks the nerve function and leads to respiratory and musculoskeletal paralysis. When eaten; even in small amounts, botulin can lead to severe poisoning.

The incidence of this disease is low. However, it poses considerable concern because of the high death rate if not treated immediately and properly.

There are three major types of botulism:

  • Food borne botulism: This is a form of food borne illness. It is caused by eating foods that contain the botulin toxin.
  • Wound botulism: This is caused by a toxin produced from a wound infected with Clostridium botulinum.
  • Infant botulism: This is caused by consuming the spores of the botulinum bacteria. They then grow in the infant’s intestines and release toxin.

    All forms of the disease can be fatal and are all considered medical emergencies.

    Food borne botulism is very dangerous as a public health problem. This is because many people can be poisoned from a single contaminated food source.

    Symptoms of Food borne and Wound Botulism

    Symptoms of the illness occur between 12-36 hours after uptake of the botulinum toxin. However, they can occur as early as 6 hours or as late as 10 days.

    Common symptoms include:

  • Dry mouth
  • Difficulty swallowing & breathing
  • Slurred speech
  • Muscle weakness
  • Double vision
  • Blurred vision
  • Drooping eyelids
  • Vomiting
  • Severe diarrhoea
  • A progressive muscle paralysis.

    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. Eventually death may occur.

    In all cases, the toxin made by C. botulinum causes the illness, not the bacterium itself.

    Infant Botulism

    Infants are especially susceptible when they are 2 to 4 months old. However, they may be at risk from about 1 week until 11 months. The infant infection may easily be mistaken for meningitis.

    Infant botulism occurs through actual infection by germinating spores in the gut of an infant.

    Symptoms of infant infection include:

  • Constipation
  • General weakness
  • Alertness despite the weakness
  • Loss of head control
  • A weak cry
  • Respiratory distress
  • Poor muscle tone
  • Poor feeding and weak sucking

    It is because of these symptoms that the infant illness is referred to as floppy baby syndrome.

    The ideal ability for botulinum spores to grow and produce toxin in an infant is enhanced by the non-acidic digestive juices of an infant, the human body temperature and the absence of oxygen in the stomach.

    Honey, corn syrup, and other sweeteners are potentially dangerous for infants as botulinum spores can survive in them.

    Botulinum spores are also are widely present in the environment - in soil, in dust, and on the unwashed surfaces of unpeeled fruits and vegetables. These spores are harmless to adults because of stomach acidity.

    An infant's digestive system is not yet developed enough to destroy them. The spores could therefore potentially cause the infant form of the disease.

    It is advised that neither honey, nor any other sweetener, should be given to children until they are weaned.

    Infant botulism develops for 1-2 weeks. It then stabilizes for 2-3 weeks before recovery begins.

    Transmission of Botulinum Toxin

    Botulism is not contagious (cannot be spread from person-to-person).The food borne form of illness is caused by eating foods contaminated with botulinum spores. These grow into bacteria and produce neurotoxin in the food.

    Botulinum toxin blocks the release of acetylcholine from nerve endings thus arresting their function.

    This toxin cannot withstand heating and prolonged exposure to oxygen. It can be destroyed if heated at 80°C for 10 minutes or longer.

    Poisoning normally occurs from the use of improperly bottled or canned foods such as green beans, beets, home-canned vegetables, cured pork and ham, smoked or raw fish, and honey or corn syrup.

    Almost any type of food that is not very acidic can sustain the growth and toxin production by C. botulinum. The disease can also occur due to improper home bottling of preservatives used in salads. Commercial canning usually destroys the spores.

    Wound botulism occurs when C. botulinum spores contaminate a wound, germinate, and grow within the wound. These produce a toxin that is absorbed into the bloodstream. It is common in crush injuries and illicit drug use.

    Infant botulism occurs when an infant consumes the spores of C. botulinum, which then grow in the baby's intestines and produce toxins. Such cases have been linked to eating honey contaminated with C. botulinim spores.

    Botulinum toxins do have beneficial uses. Doctors use them to treat certain human diseases caused by muscle problems, such as strabismus. They are also used to eliminate facial wrinkles.

    Diagnosis of BotulinumDoctors normally consider the diagnosis if the patient's history and physical examination suggest botulism. These clues are normally not enough to allow a diagnosis of botulism.

    Other diseases such as Guillain-Barré syndrome, stroke, and myasthenia gravis can appear similar to this disease. Special tests may therefore be needed to exclude these other conditions.

    Usual tests include a brain scan, spinal fluid examination, nerve conduction test (electromyography, or EMG), and a tension 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 food borne and infant botulism.

    Botulism Treatment

    Emergency hospitalisation is recommended where respiratory trouble occurs.

    Early treatment is also needed to establish a clear airway, aid breathing, and give botulinus anti-toxin. Prompt treatment considerably reduces the risk of death.

    Good supportive care in a hospital is needed for all forms of the illness. Death may occur within the first 2 weeks of the disease due to failure to recognize its severity.

    The respiratory failure and paralysis that occur with severe botulism may require a patient to be on a breathing machine for weeks.

    In addition, intensive medical and nursing care is needed. After several weeks, the paralysis slowly improves.

    If diagnosed early, food borne and wound illness can be treated with an antitoxin. The antitoxin blocks the action of toxin circulating in the blood. This can prevent patients from worsening. Complete recovery may still take many weeks.

    Doctors can try to remove contaminated food still in the gut by inducing vomiting. They can also use enemas.

    Wounds should be treated surgically to remove the source of the toxin-producing bacteria.

    Antibiotics are of little use to treat the symptoms caused by the toxin. However, health care providers use them to treat the wound disease.

    Infants are not given the antitoxin for treatment currently.

    Each case of the disease is a potential public health emergency.

    It is necessary to identify the source of the outbreak and ensure that all persons who have been exposed to the toxin have been identified and treated. All contaminated food should be destroyed.

    Complications from Botulism

    Cases of the illness can be fatal due to potential respiratory failure.

    A patient with the severe form may require a breathing machine as well as intensive medical and nursing care for several months.

    Patients who survive the bacteria poisoning may have fatigue and shortness of breath for years. Long-term therapy may be needed to help in recovery.

    Botulism Prevention

    Food borne infections often come from home-canned foods with low acid content. These include asparagus, green beans, beets, and corn.

    Other likely sources of infection include chopped garlic in oil, chilli peppers, tomatoes, improperly handled baked potatoes wrapped in aluminium foil, and home-canned or fermented fish.

    To prevent infection:

  • Home canning should be done under strict hygienic procedures to reduce contamination of foods.
  • Oils infused with garlic or herbs should be refrigerated.
  • Potatoes baked while wrapped in aluminium foil should be kept hot until served or refrigerated.
  • Home-canned foods should be boiled for 10 minutes before eating it to ensure safety. (the toxin is destroyed by high temperatures)
  • Canned foods may indicate bacteria infestation by a characteristic outward bulge. The bulge normally results from the bacteria causing pressure to rise inside the can due to gas produced as a waste product. Such cans should be thrown away.
  • Honey and other sweeteners can form an ideal medium for the bacteria to grow. Infants should therefore not be fed them until they are weaned and their digestive juices become too acidic for the bacteria to grow. Do not give honey or corn syrup to an infant under 1 year old.
  • Wound infection can be prevented by promptly seeking medical care for infected wounds and not using inject able street drugs.

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