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Making Sense of ... Botulism




What is botulism?

Botulism is a potentially fatal illness caused by a nerve toxin produced by the bacterium Clostridium botulinum. Botulism takes three forms; 'food poisoning' caused by eating foods that contain the toxin, wound botulism when a wound becomes infected with Clostridium botulinum, and infant botulism when the spores of the bacteria grow in the intestines and release the toxin.

In all its forms, botulism may be fatal, and where food poisoning is concerned, there is the added problem of identifying the source and tracing all who may have consumed it, in good time.

Where is botulism usually found?

Botulism is rare, but may occur in any country, regardless of climate or any specific environmental factors; statistics on incidence and prevalence may not be reliable in some countries, however.

How common is botulism?

In 1999, 154 cases were notified in the USA; 23 foodborne, 92 infant, and 39 'other'.

How is botulism transmitted?

Most commonly by eating foods that contain the toxin.

Botulism has resulted from home-canned foods, but also from other sources, such as garlic in oil, chile peppers, tomatoes, baked potatoes in aluminum foil, and fermented fish. Honey may contain Clostridium botulinum spores; children under one year old should not be given honey.

Wound botulism may result from poor care of a chronic wound.

Can botulism be spread from person-to-person?

Botulism cannot be spread directly from person to person; however, poor hygiene in food preparation, and lack of care in canning ad preservation may allow the bacteria to contaminate foodstuff.

Who is most at risk?

People who eat poorly prepared food, especially canned or preserved foods; home canning presents an increased risk - but in all cases, the disease is preventable.

Honey and other sweeteners are potentially dangerous for infants, partly because their digestive juices are less likely to destroy ingested spores. However, most infants with botulism have no history of honey ingestion and the source of the spores not identified in 855 of cases. Spores released from the soil by construction may be implicateded.

What are the symptoms of botulism?

Symptoms of food-borne botulism usually occur 12-36 hours after ingesting the toxin, but have been noted as early as six hours and as late as 10 days.

Wound botulism has an incubation period between 4-14 days.

Symptoms include dry mouth, difficulty in swallowing, slurred speech, double vision, muscle weakness, vomiting, and occasionally diarrhea. Later symptoms may include paralytic ileus with severe constipation, followed by whole body paralysis; death may be due to respiratory failure, with the respiratory muscles affected by the toxin.

Infant botulism, the most common form in the United States, affects infants less than 12 months of age, with 95% of cases occurring between the ages of three weeks and six months. The first symptom is usually constipation, followed by generalized weakness, loss of head control and difficulty feeding; infant botulism has been referred to as 'floppy baby syndrome'. The symptoms usually progress to a flaccid paralysis. Death will follow if the infant does not receive respiratory support.

What are the long term effects of botulism?

While death is a possible long term effect, survivors of the toxin do not carry any long-term effects; though recovery may be prolonged. indeed the lack of long-term damage has been cited as a major safety factor in the use of botulism toxin for medical and cosmetic reasons; the toxin has a role in the non-surgical treatment of strabismus, and the cosmetic uses of Botox are widely documented (but not here!).

What is the mortality rate for botulism?

!00 years ago, the mortality rate was reckoned to be about 70%; so that may be a useful guide to the riss of untreated disease. However, with somewhat improved diagnosis, antitoxins, and respiratory support, 5-10% would seem to be a fair figure for today; as always, delayed diagnosis, co-existing conditions, general weakness and age all contribute to risk at the higher end of the range.

How is botulism diagnosed?

Initial diagnosis is by the clinical picture; the signs and symptoms, coupled with the history, may immediately suggest botulism. However, many acute neurological conditions, including stroke, Guillain-Barré syndrome and myasthenia gravis may present a similar picture, and must be eliminated. The presence of the toxin in the blood, or the bacteria in the stool may be required.

Is there a treatment for botulism?

Antibiotics are of limited value in botulism, which is a disease of the toxin produced by the bacteria, not the bacteria themselves.

The primary treatment is the management of the paralysis, which usually will require ventilatory assitance, plus full supportive medical and nursing care, usually for several weeks, as the paralysis improves.

Early diagnosis of foodborne and wound botulism allows for treatment with an antitoxin which can prevent illness from progressing, but will not reverse the existing symptoms. Recovery will still take weeks. Antitoxin is not usually given in infant botulism.

Contaminated food still in the gut may be removed. Wounds will usually require surgical debridement, to remove the soyurce of the toxin.

Is there a way to prevent infection?

Clostridium botulinum is an anaerobic bacterium; it thrives in places deprived of oxygen. This is why is is associated with home canning and food preservation. Strict hygiene and careful preparation of foods for long term storage is essential.

Spores maybe airborne, and the risk to infants from contaminated sweet liquids, such as honey, should not be underestimated, though the jury is out on the infective process and disease vectors for infant botulism.

What is the botulism vaccine?

There is an experimental vaccine, but it is too early to assess its overall usefullness; it would be contraversial, as it would prevent the therepeutic applications of the toxin, including cosmetic implants.

The experimental vaccine is given primarily to laboratory workers who may come into contact with the botulinum toxin.

Can botulism be controlled environmentally?

The bacteria responsible for the disease occur naturally in soil; control is a matter of preventing it from reaching the human intestine or open wounds; normal hygiene and correct food preparation and storage procedures will avoid many cases. Appropriate would care and prompt expert advice with problem wounds will reduce the incidence of wound botulism.

Is there legal protection for workers and others?

Only the 'normal' protection against negligence by others; evodence of contaminated canned food, for example, may be actionable. Laboratory staff exercising appropritate caution are entitled to appropriate equipment and procedures.

Bibliography and Further Information Sources

If this article hasn't answered your question, email me at the address below, and I'll try to get the information you seek. I regret I cannot assist with individual cases or essays and school projects, but if it's something I've missed, I'll be happy to try and help.

Article written by Andrew Heenan BA (Hons), RGN, RMN

First Published: 18 September 2006
Last updated: 20 April 2012
© Andrew Heenan 2006


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