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Side Order of Worms?

You like fresh salmon? So do marine parasites.

The two most overrated things in the world, goes a gritty old Texas saying, are home loving and home cooking. Since the time when Julia Child first began appearing on television shows, home cooking has improved considerably in Texas and the rest of the United States. Perhaps home loving has gotten better too, since Alex Comfort, but that's fodder for another section of the paper.

Meanwhile, back on the home range, one item that seems to be best left permanently in the hands of professionals is that daredevil's delight, sushi. At a recent dinner party, a guest who spends nearly every weekend on the Gulf extolled the quality of sushi and sashimi he prepared right on his boat from the freshest of fresh red snapper. Two physicians attending the dinner immediately declared that they wanted to be excluded from any such meals. Physicians are often terrific amateur chefs, and almost always knowledgeable diners. Why the fear and loathing of sushi fresh from the sea?

Dr. Clifford Dacso, a professor at Baylor College of Medicine, recalls a case he was involved in while working in the San Diego area about a decade ago.

"A friend of mine, a professor of biology at [the University of California-San Diego] had a dinner party for 40 people. He served sushi and had put a few pieces in his refrigerator to have the following day. It was a Sunday, and he called me at home, in a panic because things were crawling out of the sushi. I went over there, and sure enough, he was right. I took it to the lab and identified the worms as a nematode, Anisakis simplex. Fully half of the guests had to be treated for the parasite."

The worm in question is a parasite of marine mammals, such as sea lions and elephant seals. The early part of its life cycle is spent in various marine fish. Along the Pacific coast, commercially important species such as salmon and Pacific rockfish (often sold as Pacific red snapper) may have an infestation rate of higher than 80 percent. An FDA study published in The Lancet in 1990 stated that the average number of anisakis larvae per an average-sized dressed salmon is 46. The study estimated that an average salmon yields about 1,000 sushi-sized slices of flesh, putting the odds of swallowing an anisakis larva at one in 22. However, since the front part of the fish is where sushi chefs prefer to obtain their slices -- and the front carries a disproportionate number of larvae in an infected salmon -- the odds improved to one in 13.

Once a live larva is ingested, it proceeds to attach itself, in the great majority of cases, to the stomach wall. This attachment in turn causes a strong allergic reaction that at first may appear to be an allergic reaction to a food. If the worm perforates the stomach wall and enters the peritoneal cavity, symptoms may suggest acute appendicitis or a gastric ulcer. Since humans are not the definitive host species for this worm, the luckiest patients simply cough up the inch-and-a-half-long creature. For most others, fiber-optic endoscopy will allow the physician to spot the worm and remove it with the endoscope's grappling tool. For maybe 10 percent or so of victims, those who have the nematode set up house in their small intestine, only a surgical resectioning of the infested portion of the bowel will rid them of the creature. Unlike the case with mankind's ancient freeloading friend the tapeworm, to date there are no drugs that can effectively kill anisakid worms.

Given these hair-raising odds, why aren't the Japanese as worm-eaten as old toadstools? The best statistics on anisakiasis from Japan are from a five-year-long study conducted between 1973 and 1977. In a country with a population, at that time, of about 110 million people, all of whom eat sushi regularly, the entire number of cases of anisakid worm infestation came to 379 -- about 76 cases per year, or one case per 1.45 million residents per year.

In Japan, the salmon used for sushi, called sake in Japanese, are always cold-smoked and then frozen before use. The nematodes and other parasites can survive the smoking process, but they do not survive being frozen to minus-four degrees Fahrenheit for 60 hours. Routine fish handling utilizes lower temperatures and longer periods of cold storage. In addition, the sushi chef in Japan has undergone an extensive apprenticeship, sometimes as long as eight years; sushi restaurants also are regularly inspected, and the chefs are educated and licensed by local governments. (One quick way to tell if the sushi chefs are properly trained in a U.S. restaurant is to observe their hands: Long fingernails, rings and even watches are considered signs of incomplete training in Japan.)

Two Japanese physicians writing in The Medical Journal of Australia also noted that there's a long and tasty roster of sea creatures never known to have harbored parasites harmful to humans, including tuna, bonito, mackerel, sardine, horse mackerel, sea bass, shrimp, cuttlefish, octopus, scallops, ark-shells, ear-shells, giant clams, salmon roe, herring roe and sea urchins.

When asked about cases of parasitic infection traced to Houston restaurants, Kathy Barton, chief of public affairs for the Houston Health Department, searched the records back for five years, the maximum time records are kept, and found none.

Still, the adventurous gourmet fisherman should leave the soy sauce and wasabi at home before heading out into the Gulf.

 
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