A Sushi Lovers' Dilemma
Eating raw fish poses risk of parasitic infection

(HealthDay News) -- Americans' growing fondness for sushi and sashimi could have severe gastrointestinal repercussions.

Recent case studies warn of a possible increase in the number of Americans who will contract anisakidosis, a parasitic infection caused by the ingestion of nematode or roundworm larvae.

Though such cases are rare in the United States , the incidence is expected to rise with the growing popularity of Japanese cuisine.

"In my country [ Japan ], where eating raw fish -- sashimi or sushi -- is very popular, anisakidosis is not uncommon," said Dr. Hidehiro Takei, a staff pathologist at the Methodist Hospital in Houston and assistant professor of pathology at Weill Cornell Medical College in New York City . "For example, in the hospital I worked for several years ago, more than two to three cases -- mostly gastric anisakidosis, not intestinal -- occurred every summer."

The ingested larvae cannot survive in a human host, but they can produce symptoms severe enough to send a sushi lover to the emergency room, according to the American College of Gastroenterology.

Within hours of consuming infected fish, a person might experience violent abdominal pain, nausea and vomiting, the U.S. Centers for Disease Control and Prevention reports. Sometimes the person will cough up the larvae, it says.

If the larvae pass into the bowel, the person can develop symptoms mimicking Crohn's disease, which causes inflammation of the digestive tract, according to the CDC.

Researchers from Japan presented two cases of intestinal anisakidosis at the gastroenterology group's annual meeting in 2007. In each case, the patient had consumed raw sardines that contained anisakis larvae that caused an obstruction in the small intestinal.

Anisakidosis in the stomach is easily confirmed through endoscopy, but small intestinal anisakidosis is more difficult to diagnose, experts warn.

It is also more difficult to treat.

In a report in the Annals of Diagnostic Pathology , Takei described the case of a 42-year-old man in Japan who had eaten raw mackerel about 12 hours before experiencing severe abdominal pain. In his case, the larva penetrated the intestinal wall. After surgery, the man made a full recovery.

"For gastric anisakidosis, the parasites are invading the stomach wall, causing severe pain," Takei explained. "Interestingly, these parasites can be found by fiber scope and removed using it. This is the typical treatment for gastric anisakidosis in Japan ."

But for intestinal anisakidosis, "surgery may be the only possible treatment," he said.

To prevent this parasitic infection, the U.S. Food and Drug Administration's Center for Food Safety and Applied Nutrition recommends that all fish and shellfish intended for raw, marinated or partly cooked consumption be "blast frozen" to -31 degrees Fahrenheit or colder for 15 hours or that it be frozen by regular methods to -4 degrees Fahrenheit or colder for 7 days.

On the Web

To learn more about sushi safety, check out information from the Colorado State University Extension.

SOURCES: HealthDay News ; American College of Gastroenterology, news release, Oct. 15, 2007; Hidehiro Takei, M.D., staff pathologist, Methodist Hospital, Houston, Texas, and assistant professor of pathology, Weill Cornell Medical College, New York City; Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta; Oct. 2007, Annals of Diagnostic Pathology ; Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration (www.cfsan.fda.gov)
Author: Karen Pallarito
Publication Date: Oct. 31, 2008
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