What is botulism and how is it caused? Condition explained after Bordeaux outbreak

With an Irish fan in intensive care with a suspected case of botulism after attending Ireland’s Rugby World Cup match in Bordeaux last weekend and at least eight others from different countries also affected, this is a big outbreak of a relatively rare illness.

What is botulism?

Botulism is a serious neurological condition caused by a poisonous toxin produced by the bacteria Clostridium botulinum. The disease occurs after eating foods containing the toxin or due to development of the spores within the intestine of young children or within wounds. Food botulism is the dominant form of the disease, and symptoms of paralysis generally appear after incubation of 12–36 hours following consumption of the toxin-containing food. Patients often require intensive care treatment and 5-10 per cent of people with the illness die.

What are the symptoms of botulism?

It initially affects the nerves in the skull and may cause blurred or double vision, difficulty swallowing or speaking, drooping eyelids, facial weakness and weakness of the tongue. As the toxin travels, further weakness in the neck and arms develops, after which the respiratory and lower body muscles are affected. Respiratory problems may be severe enough to need ventilation in hospital. Patients do not usually have a fever, and do not lose sensory function or awareness. When botulism is caught from food then nausea, vomiting, diarrhoea and abdominal cramps also occur.

How do you catch botulism?

The symptoms are caused not by the bug itself but by eating or breathing in the toxin which the bacterium releases. Botulism spores are widespread in the environment and can be found in dust, soil and untreated water. Foods that lead to botulism outbreaks include: meat products, such as sausage and cured ham; canned, vacuum-packed, smoked or fermented fish; vegetables preserved by canning; honey and cheese. Home-preserved foods are a particular risk.

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Infant botulism, which is rare in Europe, usually occurs in children under six months after they swallow botulinum spores, sometimes from food, which then produce toxins in their gut. Wound botulism occurs when the organisms get into an open wound and are able to reproduce in an oxygen starved environment. The last big outbreak of botulism in Ireland happened in the wounds of injecting drug users. Botulism is not contagious and cannot be spread from one person to another.

How is botulism treated?

There is no vaccine against botulism. An anti-toxin is available and works best when given early in treatment. Otherwise treatment focuses on tackling the symptoms, such as supporting ventilation in the event of respiratory failure.

How common is botulism?

Rates of botulism in the EU are generally low, with about 200 cases each year (0.03 cases per 100,000 people). The highest levels of cases over the past 10 years have been reported in Poland and Lithuania.

[ Irish patients warned against weight-loss procedure in Turkey after rise in botulism cases ]

If you attended the rugby match in Bordeaux last Saturday, what should you do?

The French authorities have identified the Bordeaux restaurant from where the outbreak emanated. They have warned anyone who ate there on September 4th-10th to be on the lookout for symptoms of botulism. As the incubation period before symptoms usually ends some 36 hours after exposure, anyone who doesn’t feel unwell by midnight on Wednesday is unlikely to get the food-borne illness. However, it can rarely take up to eight days for symptoms to develop.

The Health Protection Surveillance Centre (HPSC) has issued clear advice to Irish rugby supporters: “If you visited the Tchin Tchin Wine Bar (3 Rue Emile Duployé, 33000 Bordeaux) between Monday 4th and Sunday September 10th, 2023, and feel unwell please seek medical care immediately.”