GP Clinical: When botulism requires urgent care

A rare but severe form of food poisoning must always be treated as an emergency, says Dr Tillmann Jacobi.

Stephen, a 22-year-old student, came in for an emergency appointment complaining of diarrhoea and vomiting.

The night before, he had been at a barbecue with friends and had eaten foil-wrapped potatoes, home-pickled vegetables and sausages from a local organic farm.

Stephen was also worried about having blurred vision and headaches.

He was suffering from botulism, a rare but potentially very severe form of food poisoning. The clinical condition is a consequence of ingestion of sufficient amounts of the strong toxin of the gram-positive bacterium Clostridium botulinum. 'Botulinum' is the Latin word for 'sausage' and describes the shape of the bacterium.

C botulinum toxin is a neuro-toxin which affects the interaction of transmitters in the nerve synapses, leading to peripheral weakness. Symptoms usually occur within six to 24 hours of ingestion, but there are reports of cases with problems as early as four hours and as late as 10 days.

C botulinum lives commonly in the environment, for example in soil, water and sediments. It can also be present in the bowels of animals, shellfish and other seafood. There are many different types of C botulinum, but only the types A, B and E are known to affect humans.

The type of toxin used for cosmetic procedures is a purified form of C botulinum toxin type A and should be explained to patients that there is no link with the acquired botulism.

Food-borne botulism

There are three main groups of botulism: food-borne botulism, wound botulism and infant botulism.

The food-borne form is the most common, although the risk for wound botulism can vary as it is particularly connected with sharing needles in drug users.

The bacteria require anaerobic conditions in order to multiply.

Most commonly anaerobic conditions manifest in people who conserve their own fruit or vegetables at home and do not follow tight hygienic requirements in the process.

As a consequence, C botulinum might find its way into cans, bottles or vacuum-sealed bags. These containers may show the characteristic bulging due to the development of gas during the development of botulinum toxin.

Although the toxin is unstable in open air and heat, and is destroyed by cooking (at least 80 degC for a minimum of 10 minutes), this is not a reliable or safe way of destroying it. It is essential to dispose of the container carefully and ensure alertness.

The typical symptom pattern consists of visual problems including diplopia and blurred vision, vertigo, gastrointestinal symptoms such as diarrhoea or sudden constipation, vomiting and progressive weakness of the limbs.

Eventually this can affect muscle groups of the trunk, which may lead to significant respiratory problems. On examination of the patient, there is ptosis, dilated and slowed pupils, voice changes, dry mouth and muscle weakness with normal reflexes and sensation. There is usually no fever. The symptoms of botulism can resemble other conditions such as Guillain-Barre syndrome, myasthenia gravis or cardiovascular events.

The diagnosis is confirmed by the finding of C botulinum toxin in the blood or the faeces of the patient, or in the suspected food. However, taking a careful history and thinking about the possibility of the condition is the most important initial approach to take.

Treatment is symptomatic, but every case should be regarded as an emergency because the progression of symptoms may require more extensive treatment, including ventilation.

In this case, Stephen recovered in the subsequent few days and there were no other cases among his friends.

Treatment

An antitoxin for C botulinum toxin is available for treatment or for prophylaxis, but it is not widely used in the UK due to concerns about the side-effects and its general safety profile.

Usually the condition spontaneously resolves within days or weeks. There is no known immunity to the toxin and it is possible to suffer the condition more than once.

If a case of botulism is suspected, it is essential to enquire who else could be affected or at risk. This is the main way to prevent outbreaks.

Suspected or confirmed cases of botulism are notifiable, and can be fatal.

Since 1985 there have been 33 confirmed cases of food-borne botulism and five cases of infant botulism in the UK, although many milder cases are probably not reported.

Of the collected cases, three patients died as a consequence. In general, mortality worldwide is estimated to be up to 10 per cent.

Infant botulism

Infant botulism is much more common in North and South America than in Europe.

Its mechanism is different to the food-borne form: rather than ingesting the already formed toxin in food, infant botulism is caused by swallowing the spores of C botulinum - this will result in an actual infection with the bacteria. The spores can be found in the environment and at home.

They are also some of the few toxic spores which can survive in the production of honey. It is suspected that up to 10 per cent of commercial honeys may contain C botulinum spores. In adults the normal bacteria and fairly high acidity in the mature bowel will tackle the swallowed spores and prevent symptoms from developing.

However, as the bowel of toddlers is immature, the spores of C botulinum find ideal conditions for growth: a warm, chemically neutral and anaerobic environment.

Therefore parents are advised not to give honey or natural sweeteners to children below the age of 12 months.

Children will become symptomatic with feeding problems, gastrointestinal problems and general weakness, leading to the so-called 'floppy-baby syndrome'.

There is some evidence that up to 5 per cent of cases of sudden infant death syndrome could be directly related to C botulinum.

SYMPTOMS
- Diplopia and blurred vision.
- Dilated and slowed pupils.
- Ptosis.
- Vertigo.
- Diarrhoea or sudden constipation.
- Vomiting.
- Voice changes.
- Dry mouth.
- Progressive weakness of the limbs - normal reflexes and sensation.
- Respiratory problems.

KEY POINTS

- The form of food-borne botulism is the most common, although wound botulism is associated with drug users through shared needle use.

- Symptoms occur within six to 24 hours, but there have been reports of cases with problems showing as early as four hours and as late as 10 days.

- Treatment is symptomatic. Usually the condition resolves within days or weeks spontaneously.

- Suspected or confirmed cases are notifiable.

- There is some evidence that sudden infant death symptom could be related to infant botulism.

RESOURCES

- Clostridium Botulinum In The Food Chain, By Dr Rhodri Evans, Department of Industrial Microbiology, University College, Dublin, Belfield, Dublin 4. Published in Hygiene Review 1997, under the auspices of The Society of Food Hygiene Technology.

- http://www.hpa.org.uk/infections/topics_az/botulism/menu.htm - Health Protection Agency

- Nevas M, Limdstrom M, Virthavien A et al Infant botulism acquired from household dust presenting as sudden infant death syndrome J Clin Microbiol 2005; 43: 511-3

- Bohnel H, Behrens S et al Is there a link between infant botulism and sudden infant death? Bacterial results obtained in central Germany. Eur J Pediatr 2001; 160: 623-8 Review.

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