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The Honolulu Advertiser
Posted on: Sunday, February 3,2002

Fish poisoning can lead to serious health problems

By Landis Lum

Ciguatera is the most common cause of fish poisoning worldwide, and both ciguatera and scombroid types of fish poisoning can cause serious health problems, so people who like to eat fish would do well to be careful.

Some of the effects of ciguatera feel as bad as some ailment from a Harry Potter tale. You get weird skin sensations like temperature reversal (hot, feeling cold; and cold, feeling hot), numbness and tingling, the sensation that you have loose teeth, itching (especially of the palms and soles) and tooth pain — and these symptoms may last for years!

But before all this, you have vomiting, diarrhea or stomach pain that begins one to three hours (although sometimes as long as 30 hours) after eating the bad fish. Sometimes dangerous heart or blood pressure problems can occur, although deaths are rare — of the 40 or so cases a year in Hawai'i, just two people have died, in 1964.

What causes ciguatera poisoning? A nerve toxin called ciguatoxin is produced by a plankton that grows on the surface of algae that live on dead coral. Reef fish eat this plankton and are in turn eaten by larger fish, thus concentrating this toxin in their tissues, especially the head, viscera and roe.

Disturbances to coral reefs — hurricanes, heavy rains, sewage, dock building, dredging — increase the presence of ciguatera six to 24 months later.

Unfortunately, ciguatera-poisoned fish can look, smell and taste normal. Research by Dr. Y. Hokama from the University of Hawai'i John A. Burns School of Medicine led to Cigua-Check, a test you can buy that is 90 percent accurate in detecting ciguatoxin in the fish you catch. (Visit cigua.com; a kit with five tests costs $28.99.)

West O'ahu, the north shore of Kaua'i, west Maui and the Kona coast of the Big Island have the greatest number of cases. Last July 26, for instance, the Kaua'i Health Office issued a warning to avoid eating reef fish from the north shore ('Anini to Na Pali) after eight poisonings in two months caused by sea bass (roi or grouper), jack (ulua or papio) and surgeonfish (kole, kala, manini, palani, paku'iku'i, etc.). And in two weeks in February 1991, 35 poisonings were reported — nine from po'ou (wrasse) from the Big Island; the rest from ulua and 'ama'ama (mullet) off the Wai'anae coast.

Mannitol, given intravenously, particularly within the first 24 hours, may dramatically reduce neurologic symptoms in serious cases; this was discovered in 1988 by our very own Dr. Neal Palafox, director of family medicine at the UH medical school. Doctors would also recommend avoiding eating fish, fish sauces, shellfish, alcohol, nuts and nut oils for one to three months.

Scombroid fish poisoning also can be a problem. You get skin flushing that looks like sunburn on the face and upper body along with itching, hives or swelling of the lips, throat and tongue that usually appear 10 to 60 minutes after eating bad fish. As with ciguatera, there may be vomiting, diarrhea and stomach pain. You may get a throbbing headache or funny sensations around the mouth and gums. Breathing problems, hypotension (low blood pressure) or serious heart palpitations can occur. Antihistamines and even intravenous fluids or drugs may be necessary.

What causes this? Certain fish, such as ahi (yellowfin tuna), mahimahi, akule and marlin have high levels of histidine in the flesh. With improper refrigeration or preservation, bacteria can convert this histidine into histamine, which causes the above symptoms. Fish may taste normal, or seem peppery, sharp or bitter. And as with ciguatera, freezing, cooking, smoking or canning will not make the fish safe to eat.

The bottom line: Refrigerate fish promptly after capture, and avoid reef fish weighing more than 6 pounds, lest you unwillingly find yourself in a Harry Potter-like predicament!

Dr. Landis Lum is a family practice physician with Kaiser Permanente, and an associate clinical professor of family and community medicine at the University of Hawai'i's John A. Burns School of Medicine. This column is not intended to provide medical advice; you should consult your doctor.