In the continuing saga of potential perils for sushi eaters in the United States, researchers have exposed that a tapeworm once believed to infect only wild Asian fish has been detected in salmon in North American waters off the Alaskan coast.

Experts from the Czech Academy of Sciences and Alaska Department of Fish and Game, writing in the journal Emerging Infectious Diseases of the CDC, recently identified the presence of the Japanese broad tapeworm in wild pink salmon caught in the state. The Diphyllobothrium nihonkaiense was first recognized in 1986 as a human parasite.

Gruesome History Of The Tapeworm In Human Host

Back in 2012, a 40-year-old Japanese man who was fond of consuming chilled salmon had what was deemed a “watery” case of gastrointestinal condition, with a meter-length “tape-shaped object” found to emerge from his anus.

It turned out to be a case of the Diphyllobothrium nihonkaiense, which primarily survives in fish but can infect humans, bears, and wolves. The patient was given oral anti-worm medication.

The parasite has been found in about 2,000 documented cases in Japan as well as in northeastern Asia. The first such infection in North America was identified in 2008.

The team, hunting for the tapeworm larva under the microscope and confirming the species using advanced molecular technique, concluded that in light of the recent discovery, “salmon from the American and Asian Pacific coasts and elsewhere” pose likely risks for persons eating the fish raw.

How At Risk Are Sushi Lovers In America?

This tapeworm infection usually comes with no symptoms, but sometimes it can be accompanied by abdominal discomfort, vomiting, diarrhea, and weight loss, the CDC noted. Vitamin B12 deficiency resulting in pernicious anemia, as well as complications such as obstruction of the intestines and gall bladder disease, may also take place.

Infection can occur by eating raw or undercooked fish, including salmon, perch, trout, and usually other freshwater species. Salmon, for instance, live in both fresh and salt water and could contain the tapeworm either way. Fish could harbor the infectious organisms when lightly salted, smoked, or pickled.

As a form of precaution, the FDA recommends cooking fish to an internal temperature of 145 degrees Fahrenheit at a minimum and freezing at -4 degrees Fahrenheit or below for seven days. The infection can be treated using medications such as praziquantel or niclosamide.

The good news is the likelihood of acquiring a tapeworm in the United States is quite low, with most of its counterparts in Japan going unnoticed. Consuming pork or beef too yields only around 1,000 new tapeworm cases every year.

Study author Jayde Ferguson pointed to improvements in identifying in distinguishing the tapeworm from other types of the parasite.

“This worm has always been here, and we’re just getting better at identifying it.”

It could have been worse for seafood lovers. In August last year, findings of laboratory tests conducted by the FDA found hepatitis A in scallops suspected as the possible source of an outbreak of the virus, which sickened at least 206 people in Hawaii.