Raw-fish eaters face parasite infections

Nutrition Health Review, Wntr, 1989

Raw-Fish Eaters Face Parasite Infections

Parasite infections of people who eat raw or undercooked fish are increasing, and the main cause is said to be the rising population of seals and other protected marine mammals. Creatures such as dolphins, sea lions, and seals are normally heavily infested with two types of nematodes whose eggs the mammals expel in their feces. The immature wormlike larvae are then eaten by tiny shrimplike crustacea, which in turn are eaten by squid and some fish -- and can end up in the stomachs or intestines of humans.

A medical rarity in the United States until recently, human infection by the parasites, called Anisakidae, has increased markedly. Fifty cases have been reported -- 70 percent of them since 1980 -- but they may be the "tip of the iceberg" because the infection is difficult to diagnose, according to scientists writing in the latest issue of the New England Journal of Medicine.

They attribute the increased U.S. incidence to the legal protection of the mammals, starting in 1972, and to the current popularity of raw fish, such as sushi and sashimi, served in Japanese restaurants. When consumed in raw or undercooked fish, the worms enter the intestine or stomach, where they die, but before dying they cause inflammation and pain resembling symptoms of other, more common diseases, such as appendicitis, gastric ulcers, or stomach cancer.