Sickening fish parasite lowers sashimi demand in Japan

Published on
July 13, 2017

Japanese television news shows have recently featured several segments about the parasitic nematode Anisakis simplex, which can be transmitted to people when they eat raw fish that has not been previously frozen to below 20 degrees Celsius. 

The publicity about the parasite, which causes violent abdominal pain, nausea, and vomiting in those who consume it, has depressed sashimi sales throughout Japan. The wholesale prices of a few species, such as sardines, have fallen as a result. 

Larvae of the white, string-like parasite are about five millimeters wide and up to three centimeters long. They are often found in mackerel, Japanese horse mackerel, salmon, saury, sardines and squid. In English, it is sometimes called “herring worm.”

Although anisakis has been known as a parasite in Japan for a long time, reports of illnesses caused by it have increased in recent years. Japan’s Health, Labor and Welfare Ministry reported that the number of anisakiasis cases increased from only four in 2004, to 79 in 2013, and 126 in 2016. This increase in the number has prompted the news reports and greater public concern.

This increase may or may not be due to a change in the amount of parasites in the fish. It is possible that with greater access to information through the Internet, people with mild symptoms are better able to identify their problem and seek medical help. 

However, it is also possible that an increase in whale numbers since the banning of commercial whaling has contributed to an increased in anisakis infestations in fish. The parasite grows and lays eggs in the stomachs of marine mammals such as seals, sea lions, dolphins, and whales. The eggs enter the ocean through the mammals’ feces and are eaten by krill, which may then be eaten by fish, which are in turn eaten by humans. 

Peak demand for horse mackerel and sardines usually arrives with summer, but the demand for fresh product for raw consumption is likely to be softer this year due to concerns over the parasite.

Contributing Editor reporting from Osaka, Japan

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