Botulism is a toxi-infection due to a mighty bacterial neurotoxin called botulinum toxin. It is a group of seven toxins produced by the Clostridium botulinum, the spores of which are present in soil and the organism of some animals (fish included). When spores sprout, they generate vegetative bacteria that produce toxin. Botulism affects humans and animals. It is a rare disease: 0.001 case/100,000 inhabitants per year in Belgium (but it is an underestimation). It is present everywhere in the world.

Botulism and botulinum toxin are not contagious. Transmission from one person to another is thus impossible. Infected persons do not represent any menace for the others and do not have to be placed in quarantine. However, if it was intentionally modified to produce botulinum toxin, the bacilli could be contagious. After diffusion of toxin by aerosol, there is no risk of contamination from person to person.

Contamination mode

Botulism can naturally show under the three following forms:

• The most frequent form is foodborne botulism. It is a severe food intoxication caused by ingestion of food prepared or kept under a form allowing the production of toxins. The bacteria produce toxins in food kept under vacuum and that have not been sufficiently cooked. Toxin is directly ingested with the contaminating food, generally salt meat or fish, cooked pork meats, and home-canned food.
• Botulism can also be caused by infection of a skin wound (rare). The toxin passes then directly into general blood circulation. It does not pass through intact skin.
• Infant botulism is the most frequent form of botulism in the United States. It is caused by ingestion of spores and anarchic proliferation of intestinal flora. That form of botulism could also affect adults with a fragile intestinal flora.

Intentional propagation:

• Botulinum toxin could be intentionally propagated by aerosol and in that way trigger off the affection by inhalation. In principle, this contamination mode is excluded. Neurological symptoms are not preceded by gastro-intestinal symptoms, as it is the case with food intoxication.
• Botulism can also be transmitted by water. That transmission mode is also exceptional. Theoretically, it would be possible to propagate the disease by contaminating drinkable water with a toxin, but the latest does not resist to most of water purification methods. Besides, the dilution effect is enormous.

Botulism symptoms

The incubation period in case of food contamination ranges, most of the time, from 12 to 36 hours but can sometimes be of up to several days. The stronger the infection dose is, the shorter the incubation period.

The most typical symptoms are the sudden neurological symptoms, starting most of the time with an effect on cranial vessels (drop of visual acuity, diplopia, dysphagia, dysphonia and mouth dryness), followed by a slow and descending symmetric paralysis. Vomiting is frequent due to paralytic ileus. Diarrhoea rapidly gives way to constipation. In general there are no fever or disorders of consciousness.

Recovery can take months.

All forms of botulism show the same symptoms but the seriousness of the disease can considerably vary. In case of contamination by inhalation, gastro-intestinal symptoms do not precede neurological symptoms. Infant botulism provokes constipation and general hypotony that can cause respiratory failure and finally death.

Mortality

Mortality by foodborne botulism is of the order of 5 to 10 % in the United States. Mortality in newborn children hospitalized for botulism is inferior to 1 %.

Diagnosis

The diagnosis is clinical.

Clinical signs here above described along with a careful anamnestic interview will be most of the time enough to establish a diagnosis. An electromyography can reveal useful in some cases. Cerebrospinal liquid remains unchanged in case of botulism. A microbiological diagnosis and a post mortem diagnosis can also be carried out.

Treatment

Treatment of botulism is symptomatic and surveillance implies hospitalization, sometimes in a reanimation unit, due to the risk linked to deglutition disorders and/or to heart rhythm disorders than can occur even in moderate forms. Assisted ventilation (artificial breathing) can be necessary and justified during several weeks.

Prevention

Botulism remains a disease provoking serious clinical complications. It can sometimes be avoided thanks to an adequate preparation of food. It relies upon simple hygiene rules in home canned-food (industrial production is generally safe from intoxication). Preservation processes must be scrupulously respected. Control of temperature, saline concentration and PH is essential. Foods preserved under vacuum always have to be sufficiently cooked.