Ciguatera poisoning

This is a type of fish food poisoning which occurs when someone eats fish which have become infected by toxins that are produced by seaweed, algae or coral. These are usually found in tropical seawaters.

Another similar type of food poisoning is scombroid poisoning which is discussed separately.

The symptoms of this are very similar to food poisoning but can last for a long period of time. In some cases they persist for several years, resulting in long term debility.

Causes of ciguatera poisoning

Ciguatera is the name given to food poisoning caused by the ciguatoxin – a type of toxin found in some species of tropical fish. Other types of toxins include maitotoxin and palytoxin.

This is produced by organisms called ‘dinoflagellates’which live in both sea and fresh water environments. They attach themselves to seaweed or algae where they are consumed by fish, living in these waters.

Note: algae are a type of organism that has a similar appearance to seaweed.

There are around 5 types of ciguatoxin.

What happens is that small, plant eating fish consume these algae only to be themselves consumed by larger, meat eating fish. This enables these toxins to move higher up the food chain where they build up in strength over time.

So, if you eat fish which has consumed algae which is infected with these toxins then you will develop ciguatera food poisoning. Examples of infected fish include sea bass, red snapper, eel and Spanish mackerel.

Symptoms of ciguatera poisoning

Ciguetera poisoning affects the digestive, neurological and cardiovascular systems. The symptoms appear quickly, often within 12 hours of consuming infected fish.

They include:

• Nausea
• Stomach pain
• Vomiting
• Diarrhoea

These are the first set of symptoms to appear and last for a couple of days. These affect the digestive system.

The next set of symptoms affects the neurological system. They include:

• Poor co-ordination/lack of balance
• Mental confusion
• Pain in the teeth (may feel loose)
• Dizziness
• Muscle pains
• Joint pain
• Headaches
• Hallucinations

These symptoms can appear in as little as a few hours or after several days following consumption. They can persist for up to several months.

The third set of symptoms affect the cardiovascular system. They include a very slow heart rate and high blood pressure which can cause dizziness and physical weakness.

Sweating, chills and a stiff neck are other symptoms of ciguatera poisoning.

Complications include long term fatigue, persistent headaches and difficulty with balance and co-ordination.

Treatment for ciguatera poisoning

Ciguatera poisoning cannot be cured. The disease is managed and supported instead with the aim of helping someone to recover rather than an outright ‘cure’.

Most people recover but it takes a long time to do so.

Some people suffer a relapse, often following contact with certain allergens which may cause long term damage.

Medication such as calcium channel blockers, e.g. Verapamil may help to treat some of the symptoms which occur after the initial digestive stage.

Vitamin supplements and steroids can support recover rather than reducing the effect of the toxin.

Preventing ciguera poisoning

One way is to avoid eating large amounts of shellfish especially those which live in tropical waters. This is because the ciguatera toxins tend to live in tropical (and sub-tropical) seas such as the Pacific Ocean.

For more information on this and other toxins visit our shellfish toxins section.