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Fish Poisoning More Common Than Believed

The New York Times, June 29, 2015

Poisonings from a toxin carried by barracuda and other sport fish have been seriously underestimated in Florida, according to a new study — and the problem is far more common in fishing communities around the world than has been recognized, the lead author said.

In Florida, poisonings from the ciguatera toxin were highest among Hispanics, presumably because they are more fond of eating barracuda, according to the study, which was published this week in The American Journal of Tropical Medicine and Hygiene.

Ciguatera (pronounced sig-WAH-terra) is produced by algae that grow in warm water, and there is a risk of it spreading north as ocean waters warm, said Elizabeth G. Radke, an epidemiologist at the University of Florida’s Emerging Pathogens Institute and the lead author of the study.

The poison is picked up by coral reef fish that eat vegetation and concentrates in larger carnivorous fish that eat them. The highest levels are found in barracuda, but it is also found in grouper, amberjack, hogfish, snapper, mackerel and mahi-mahi. Neither cooking nor freezing affects the toxin.

“We recommend not eating barracuda at all,” Dr. Radke said. For the rest, which are common in fish markets, “it’s a good idea to be aware that you’re taking a risk. If you get ill, see a doctor, tell them you ate fish, and if you have some fish left, freeze it so it can be tested.”

Fish caught in colder northern waters are unlikely to be have the toxin, she said, but the risk is not zero, because fish migrate.

Severe vomiting within three hours is the most common symptom, but some people have pain and tingling in the mouth, hands and feet, and sometimes leg weakness. Most cases recover, but in some people, the neurological symptoms, including hot surfaces, feeling cold and vice versa, last for months.

There is no specific treatment, although mannitol, a type of sugar with many medical uses, appears to help, Dr. Radke said.

Dr. Radke’s study combined analysis of poisoning reports and an email survey of more than 5,000 sport fishermen. Ciguatera poisoning is supposed to be reported to the state by Florida doctors who diagnose it, and the official estimate is one case per 500,000 residents a year.

Dr. Radke’s study estimated that it is 28 times more common. Ciguatera poisoning occurred most frequently in people who fished near Miami, the Florida Keys, and the Bahamas, but it was rare in northern Florida. Poisonings were three times more common among Hispanics compared with other ethnic groups.

The illness, often called just “fish poisoning,” is well known in areas around warm water in the Caribbean, the South Pacific, and the Indian Ocean, she said. A survey Dr. Radke did in St. Thomas, V.I., found that 25 percent of all residents had experienced it, and half of those had had symptoms that lasted more than three months.