Eat Raw Fish ... Get a 9-Foot Tapeworm

Tapeworm cases from raw fish have jumped in urban areas in recent years.

June 15, 2009, 7:31 PM

June 16, 2009— -- One summer day in August 2006, Anthony Franz went to a Chicago area hospital carrying a 9-foot worm.

He did not find it in his garden.

Franz is one of the few, but growing number of tapeworm victims in cities across the world who are discovering (or rediscovering) that some of the most popular fish can host parasites.

Although still rare, a study this June showed salmon tapeworm infestations tripled from an average of 0.32 cases per 100,000 people each year in Kyoto, Japan, to at least to 1 case in 100,000 people in 2008. As more people adopt sushi and undercooked fish diets around the world so too, has the worm spread.

The article, printed in Emerging Infectious Diseases, tracked the movement of tapeworm infection for 20 years as reports migrated from rural fishing villages in Japan to urban centers around the world, including France, Switzerland and the United States.

"Usually, with this particular warm it produces discomfort, some pain, and it can produce anemia," said Dr. Felipe C. Cabello professor of Microbiology and Immunology at New York Medical College in Valhalla.

A more dangerous worm, a nematode called anisakis, can burrow into the stomach wall and require surgery. But Cabello said the fish tapeworm can still slowly drain a person's energy.

"The parasite sucks the vitamin B12, and the person with the parasite does not have enough," said Cabello. "This is a worm that can reach 25 feet and it might take months, a year to grow."

In 2008 a Czech tourist fell ill from eating raw sockeye salmon in Vancouver, Canada. According to an article in The Oregonian, the man only discovered a tapeworm when he returned home. Other forms of salmon tapeworm have been found in sushi-eating urbanites in Brazil, according to a July 2007 report in Emerging Infectious Diseases.

In Franz's case, the offending creature was the Diphyllobothrium latum. Franz was not available for comment and is suing an Illinois seafood restaurant for $100,000.

"Basically we discovered that this particular tapeworm was caused from uncooked seafood, particularly salmon," said Franz's attorney, Gregory Leiter. "That's what he brought into the hospital."

Why Fish Carry Parasites

Leiter charges the parasite came from "uncooked seafood salad," at Shaw's Crab House in downtown Chicago, a restaurant that's part of the greater Lettuce Entertain You Enterprises of Chicago.

"From the reports we've seen, and the people we spoken to, we're very confident that he did not get this tapeworm from food at our restaurants," said Kevin Brown, president CEO of Lettuce Entertain You. "In each of our restaurants food safety and proper food handling is the number one priority," he said.

Whatever happened at that restaurant, it's clearly possible to get a fish tapeworm in the United States.

"Chefs sometimes joke if the worms are moving then the fish is fresh," said Helen Rennie, author of the blog Beyondsalmon ( and owner of Helen's Kitchen cooking school in Boston.

"When I used to work in a restaurant I found that the fish I got was a lot more wormy than the fish I get in the store," she said. "It's natural."

Rennie, who specializes in fish dishes, said large tuna varieties such as blue fin, yellow fin and big eye are usually parasite-free. But Rennie said trout, cod and wild small salmon such as sockeye and coho (not king salmon) are prone to parasites.

In fact many grocery stores sell fish that's been through "candling" to remove surface parasites.

"They put fillets on glass and shine strong light through and pick it out worms with tweezers," she said. "They do that so you don't go to back to [the store] and rip the fishmonger's head off."

Disgusting as parasites may sound, fish safety officials, parasitologists and cooks say most of us should relax. It only takes cooking the fish to kill off the parasites.

"I always hear, 'oh my god, I'll never cook fish again -- but if you have ever eaten a fish dish before you, I promise you have eaten parasites before," said Rennie. "But if you are serving it raw at home -- I don't suggest anybody do that without any real training."

According to U.S. Food and Drug Administration regulations, all fish meant to be served as sushi must be frozen for a specified period of time (usually a week) to kill lurking parasites.

Learning to Safely Eat, and Cook Fish

Rennie said no matter how fresh, unless you're buying certified "sushi grade" fish it's best not to try to serve it raw at home.

"Parasites are really a non-issue, it's not as big of a problem as time and temperature holding," said Pamela Tom, Seafood Network Information Center Director at the University of California, Davis. "People focus on methyl mercury, but in reality it's not as important as the bacteria."

"I'd say overall the nation is not at risk," she said.

Indeed, many other countries still see fish tapeworm more often than the raw-fish aficionados in the United States.

"There was one big recall a couple years ago in California where someone brought in fresh salmon from up north to a restaurant," said Scott Lyell Gardner, curator and professor at the Harold W. Manter Laboratory of Parasitology at the University of Nebraska - Lincoln.

"People get it very commonly, especially in the northern parts of the world -- in Norway, Finland, Canada," he said.

Gardner said the fish tapeworm naturally moves from larval stages in fish to adult stages in bears (or sea mammals). The large mammals then excrete the eggs back into the water to start the process all over again.

"The main life cycle is bear-salmon, bear-salmon, and people get into it when they eat salmon," he said. Bottom line: cooking makes the fish safe. To stop this cycle, cook your fish."

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