By Amy Norton

NEW YORK, Mar 13 (Reuters Health) - In a world overburdened with high cholesterol and reports of mad cow disease, a tuna burger may seem a safer alternative to the traditional red-meat variety. But when the fish is handled improperly, a bite into a tuna burger can be a stomach-churning experience, according to a report in the March 14th issue of The Journal of the American Medical Association.

Health officials traced 22 cases of food poisoning in North Carolina to contaminated tuna, mostly in burger form and nearly all from restaurant dishes. Although they could not zero in on which points between sea and burger bun the fish became tainted, poor temperature control is likely to blame, according to researchers led by Dr. Karen Becker of the Department of Health and Human Services in Rockville, Maryland.

Of the 22 people who were sickened by histamine, a toxin that can develop in tuna and some other fish, 18 had eaten tuna burgers. The four others had eaten either tuna salad or tuna filet. Tuna burgers are susceptible to contamination because they are prone to "temperature abuse," Becker explained in an interview with Reuters Health.

The safest way to handle fish is to transport it from "ice to stove," according to Becker. But tuna burgers may have gone through a wave of temperature changes before they get to people's plates. For instance, Becker said, the grinding process heats up the fish. But this hot-and-cold shift can begin on the boat, where newly caught fish may not be adequately chilled. At every step afterward--from trucking to markets to preparation at restaurants--inadequate temperature control can increase the chances that bacteria will thrive.

Becker's team found temperature-control violations in two of five restaurants investigated, which accounted for two thirds of the food poisonings.

Histamine poisoning takes hold quickly, sometimes within minutes, and causes symptoms such as burning around the mouth, headache, rash, stomach cramps, nausea and diarrhea. In this study, there were no hospitalizations or serious complications.

In the one recent case that did not involve a restaurant, Becker noted, the woman bought a fish, then traveled for several hours with it in her car. For consumers, getting fish at least "close to freezing" quickly is vital, Becker stressed.

"It's not safe enough to keep it at temperatures cold enough for meat and poultry," she said.

On a larger scale, Becker and her colleagues write, investigators need a simple test that is sensitive enough to catch histamine contamination before it gets to the dinner table.

Between 1988 and 1997, histamine fish poisoning was reported in 145 outbreaks involving 811 persons from at least 20 states, according to the Centers for Disease Control and Prevention.

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