Tropical fish on restaurant menus can be poisonous.
When Dr. Juan Behar and his wife Sandra ordered amberjack in a Providence, Rhode Island seafood restaurant, they thought they were consuming nothing more exotic than a tasty tropical fish. But at dawn the following morning, Sandra, a nurse, woke with a racing pulse - her heart was beating 140 times a minute, her skin was flushed, she felt anxious and confused. Dr. Behar, now the Director of the Division of Gastroenterology at Rhode Island Hospital in Providence, called Sandra's boss to report that she was too sick to come to work.
“The next thing I knew, I woke up in the hospital,” Dr. Behar says. His daughter had discovered him lying unconscious on the bathroom floor, victim of a seizure. Hooked to a respirator, he was receiving massive intravenous doses of mannitol meant to ease the pressure in his dangerously swollen brain. Sandra was stricken with severe vomiting, diarrhea, and delirium.
The unsuspecting Behars had been blindsided by ciguatera poisoning, an illness brought on by the consumption of tropical fish that have been contaminated by eating toxic dinoflagellates found in seaweeds, sediments, and coral rubble. Worldwide, ciguatera affects between 10,000 and 50,000 seafood consumers every year. “It was a very scary experience,” Dr. Behar says. “I'm very fortunate to be alive.”
There is no proven test for ciguatera poisoning, either in patients or contaminated fish. Over 175 gastrointestinal, neurological and cardiovascular symptoms have been recorded. Diarrhea, abdominal pain, and nausea usually appear within 24 hours of eating the ciguatoxic fish; the illness can progress to include numbness, itching or tingling of lips, hands and feet, low pulse rate, high pulse rate, dizziness, severe fatigue, hair loss, rashes, anxiety, depression, and a reversal of temperature sensations in which cold objects feel hot to the touch and scalding items feel like ice.
These symptoms are often bewildering to doctors who minister to stricken tourists returning from the tropics or to patients who eat tainted fish in inland cities. Dr. Behar attributes his own survival to a neurologist at the hospital who by chance had recently read an article on ciguatera poisoning.
Although fatal attacks are relatively rare, symptoms can linger for months or even years. Astringent foods such as liquor, wine, vinegar, and pickles can trigger relapses. Four years after their ciguatera poisoning, Sandra Behar suffers from recurrent stomach cramps, and the soles of Dr. Behar's feet are numb.
Ciguatoxic fish are found primarily in island waters, in areas free from terrestrial run-off. It is endemic in the Caribbean, South Pacific, and Australia's Great Barrier Reef, and in virtually all subtropical waters of the United States, including Florida, Hawaii, Guam, the US Virgin Islands, Puerto Rico, and many Pacific Territories. Ciguatoxic species include mahi-mahi, red and yellow-tail snappers, grouper, barracuda, red bass, and moray eel.
Ciguatera poisoning is not a new phenomenon. Spanish colonists in the Caribbean blamed the sickness on a marine turban snail called “cigua,” and it struck Captain Cook in New Caledonia in 1774. Later theorists blamed diseased fish or pollution. Only recently have researchers traced the sickness to the dinoflagellate Gamberdiscus toxicus, a dinoflagellate that lives attached to bushy red, brown, and green seaweeds and also occur free in sediments and coral rubble. Herbiverous fishes eat the seaweeds and the attached dinoflagellates. Since ciguatoxin is soluble in fat, it lodges in the fishes' tissues and travels up the food chain as the smaller fish are eaten by predators. The largest, oldest, and thus most desirable fish are often the ones that have accumulated the most toxin and are the most dangerous.
For residents of the tropics, ciguatera poisoning is not only a health threat, but it makes a potentially lucrative export product undesirable in international markets.
Don Anderson does not eat local fish when he travels to the tropics, and he warns seafood lovers to be wary of reef-dwelling tropical fish sold in mainland restaurants. Although much progress has been made in ciquatera research, many toxicological, physiological, and ecological mysteries remain about this illness and its dinoflagellate source. Says Anderson, “This is a marine phenomenon that will give up its secrets very slowly.”
Copyright © 2002 Tom Gidwitz
Fish pictures copyright © 2001 WASCO