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Tuesday, 31 October, 2000, 01:01 GMT
Fish food poisoning breakthrough
Barracuda
Eating barracuda can lead to ciguatera poisoning
Scientists may have uncovered a treatment for a bizarre illness triggered by eating certain exotic fish.

Ciguatera can be likened to some types of shellfish poisoning, in that it is caused by naturally occurring toxins which are not destroyed by cooking.

The toxin which causes ciguatera is found occasionally in predatory reef fish such as jack, grouper, barracuda and snapper.


We now have the potential for a simple bedside test

Dr Ritchie Shoemaker

Up to a million cases of the illness are reported worldwide each year, although it is hard to diagnose, so there may be more which have not been identified, or even mislabelled by doctors.

The illness generally occurs in tropical areas, but can occur anywhere the fish are imported and eaten.

Symptoms can include chronic fatigue, and other food poisoning symptoms such as upset stomach.

The tiredness can persist for years, and be joined by other neurological symptoms such as a metallic taste in the mouth, a burning sensation in the arms, and strangely, the reversal of hot and cold sensation on the skin.

The illness can also cause a loss of mental ability.

Misdiagnosis

Doctors not familiar with ciguatera sometimes mistakenly give a diagnosis of chronic fatigue syndrome.

Until recently, doctors have had neither a decent test for ciguatera, or a treatment, but Dr Ritchie Shoemaker told the annual meeting of the American Society for Tropical Medicine and Hygiene both may be on the horizon.

"The explosive onset of an acute ciguatera illness can be readily identified clinically, but there is no consistent mechanism available to confirm the diagnosis in chronic cases," said Dr Shoemaker, of the Pfiesteria Illness Center, Maryland.

He is now employing a vision test used by the US Air Force which checks the ability to discriminate between white, black and grey - the lack of which is another symptom often seen in chronic ciguatera.

He said: "We now have the potential for a simple bedside physiologic test."

In addition, a drug currently used to treat high cholesterol levels could be able to deal with the toxin which causes ciguatera.

In 10 patients tested by Dr Shoemaker, cholestyramine doses managed to correct the vision problems and end other chronic symptoms, some of which had been present for 10 years.

The "cure" took effect within only a few months of taking the drug.

The drug works because its molecular structure matches receptors on the toxin, locking them together and inactivating the poison.

A spokesman for the Public Health Laboratory Service said the illness was rare in the UK.

He said: "We see occasional cases. It mainly happens to people who have eaten imported fish, or who have returned from holidays to tropical countries."

A full clinical study of both test and drug is planned.

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