Japanese Tapeworm Found in Alaskan Salmon

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Wild salmon caught in Alaska is infected with a parasite, the Japanese tapeworm, says a study published by the Centers for Disease Control and Prevention (CDC). 

Researchers identified four species of Pacific salmon infected by the Japanese Broad Tapeworm — a parasite discovered in 1986 that can grow up to 30 feet long in your digestive tract.

“We detected Diphyllobothrium nihonkaiense (Latin name of the Japanese Broad Tapeworm) plerocercoids (a larval form of the tapeworm) in the musculature of wild pink salmon (Oncorhynchus gorbuscha) from Alaska, USA. Therefore, salmon from the American and Asian Pacific coasts and elsewhere pose potential dangers for persons who eat these fish raw”, Cdc.gov reported in its February 2017 edition of Emerging Infectious Diseases.

The Japanese Broad Tapeworm is the second most common causative agent of diphyllobothriosis infection in humans.

Researchers examined, in July 2013, 64 wild Pacific salmon of 5 species: 1 chinook salmon, 1 coho salmon, 23 pink salmons, 8 rainbow trouts, and 31 sockeye salmons in south-central Alaska. They found a larva of the D. nihonkaiense tapeworm.

japanese tapeworm in salmon
Pacific salmon is frequently exported unfrozen, on ice, and parasites may survive.

How bad is the Japanese tapeworm?

Until now, it was believed that the Japanese tapeworm only infected fish in Asia and Russia. Now, the research team concluded that this is an evidence that salmon from the Pacific coast of North America may represent a source of human infection. This is because Pacific salmon is frequently exported unfrozen, on ice, which may lead to surviving of the parasites. In this way, they cause human infections in areas where they are not endemic, such as China, Europe, New Zealand, and middle and eastern United States.

That’s not to say you need to eliminate salmon from your diet completely. You can eliminate any risk of Japanese tapeworm by properly cooking or freezing the fish.

In 1986, the Japanese Broad Tapeworm was recognized as a human parasite separate from the most common broad fish tapeworm, Diphyllobothrium latum, in Japan. Diphyllobothrium latum and related species are the largest tapeworms, that grow up to 30 feet long, and they can infect people with diphyllobothriosis.

About 2,000 cases of diphyllobothriosis have been reported, mainly in northeastern Asia. However, recent studies indicate that the number of human cases caused by this tapeworm may have been highly underestimated.

Diphyllobothriasis can be a long-lasting infection. Most infections are asymptomatic. Manifestations may include abdominal discomfort, diarrhea, vomiting, and weight loss. Vitamin B12 deficiency with pernicious anemia may occur. Massive infections may result in intestinal obstruction.

According to the U.S. National Library of Medicine, treatment is important because fish tapeworm infections can cause serious problems.


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