What is Anisakis, the number one cause of food poisoning in Japan, and how can we avoid it?

Naomi Watanabe is seen in Shibuya Ward, Tokyo, December 12, 2017 (Mainichi/Toshiki Miyama)

TOKYO – The number of reported cases of food poisoning due to Anisakis, a parasite that enters the human body when sashimi is eaten and causes severe abdominal pain, is increasing in Japan.

In 2018, it became the leading cause of food poisoning in the country. Anisakis is a fearsome parasite that bites into the walls of the stomach and intestines, causing severe pain and nausea due to allergic reactions.

On June 26, Tomomi Itano, 30, a former member of the popular Japanese idol group AKB48 and now a TV personality, reported on her YouTube channel that she had suffered from anisakiasis.

How can we prevent that?

“Aniki attacked me,” “Aniki frightens me.” Blogs and social media sites for fishing enthusiasts are lined with posts about Anisakis, nicknamed Aniki, with horror and fear in mind.

Anisakis linear shaped found in mackerel appears on a fingernail. (Photo courtesy of the Fish Meal Promotion Center of the Japan Fisheries Association)

According to the Food Safety Committee of the Cabinet Office of Japan, Anisakis is a nematode that is 2 to 3 centimeters long. It passes from krill, a type of plankton, to fish including mackerel and horse mackerel, and through the food chain becomes adults in the bodies of marine mammals such as whales, dolphins and Steller sea lions, which are the ultimate host. The eggs are then released into seawater mixed with feces, and the hatched larvae are eaten by krill and reintroduced into the food chain.

During its life cycle, Anisakis is traced to the stomachs and intestines of humans who have eaten raw fish. Anisakiasis first appeared in written records in 1876 with a case in Greenland, in the Arctic Circle. Then, people who ate salted herring in Holland in the 1950s and 1960s fell ill one by one. The first case was reported in Japan around this time.

According to the Department of Health, Labor and Welfare, food poisoning is classified by cause into: (1) bacterial, such as salmonella; (2) Viral, such as norovirus; (3) Parasitic such as Anisakis. (iv) Chemicals, such as agrochemicals; and (5) a natural poison, such as pufferfish and poisonous mushroom poison. Anisakis was classified as a causative agent of food poisoning under the Food Sanitation Act in 1999.

In 2013, there were 88 cases of food poisoning in Japan from Anisakis, 9.5% of the total, but in 2017, the number exceeded 200. A series of reports of notorious food poisoning by celebrities in 2017 helped raise awareness of intestinal infections. For example, TV personality Naomi Watanabe stated on Twitter that she was in “extreme pain” and recalled, “I cried in the hospital.” Ryota Yamasato, half of the comedy duo Nankai Candies, and Tomoharu Shoji, half of the comedy team Shinagawa Shoji, also revealed during TV shows that they suffered Anisakis damage.

It exceeds food poisoning caused by Hakimia Campylobacter mainly found in chicken, and norovirus, in case numbers, and represents the largest number of outbreaks since 2018. There is no limit to the number of restaurants that are suspended.

Tadatoshi Hayataki, division head of the Fish Meal Promotion Center of the Japan Fisheries Association, is seen in the Minato Ward, Tokyo, June 20, 2022 (Mainichi/Isamu Gari)

On June 26 this year, former AKB 48 member Itano stated on her YouTube channel that she had removed Anisakis, saying that the isisakis was “extremely painful.” Her post brought the public’s attention back to nematodes.

Jun Suzuki, a board member of the Japanese Society of Parasitology and chair of the clinical microbiology division at the Tokyo Metropolitan Institute of Public Health, cited “increased awareness of Anisakis” as the main factor behind the increase in cases, but also noted that this number is “the tip of the iceberg.” Medical institutions are not fully aware of the need for notification, and there are estimates of about 7,000 cases of anisakiasis annually in Japan based on data from those institutions.

To avoid anisakiasis, the Department of Health recommends that fish be frozen at minus 20 degrees Celsius for at least 24 hours or heated at 60 degrees Celsius for at least one minute. Anisakis moves from the internal organs to the muscles when the fish die, so in addition to looking for the nematodes with your eyes to remove them, the ministry also demands that the internal organs be removed immediately after the fish are caught.

Can’t we “neutralize” it with the power of wasabi, which is said to have germicidal properties? According to Suzuki, “It may be somewhat effective if you swallow a tube of wasabi,” which gives you a little bit of hope. Also, Anisakis do not die when vinegar is applied or dipped in soy sauce, so people need to be careful.

Tadatoshi Hayatake, department head of the Japan Fisheries Association’s Fish Meal Promotion Center, which has been promoting fish consumption, recommended “heating or freezing the fish if you’re concerned,” but added, “The parasitism (Anisakis) changes depending on the type of fish, its habitat, and the season. Minimizing risks when consumers judge each fish individually, so I hope that each of us can become a connoisseur and enjoy the richness of seafood.”

(Japanese original by Isamu Gari, Digital News Center)

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