The Centers for Disease Control and Prevention revealed in a new study that the Japanese broad tapeworm has been found in Alaskan salmon, despite the parasite typically existing only in Asia’s Pacific coasts, and nowhere near North America.
A new study conducted by the CDC’s Emerging Infectious Diseases department revealed how the Japanese broad tapeworm now exists in wild salmon caught in Alaska, after primarily being associated with fish caught in Asia. According to USA TODAY, any salmon caught anywhere off the Pacific coasts in North America could be at risk of being infected, and while the health impact on humans isn’t thought of to be serious, the CDC’s scientists believe that the tapeworm could spread out even further if things aren’t nipped at the bud.
Alaskan salmon and other fish targeted by the parasite aren’t frozen, but are packed and transported on ice. That means Japanese broad tapeworm larvae may survive shipment trips, and may potentially spread to other continents, affecting residents of China and New Zealand, as well as those in Europe and other U.S. regions apart from the Pacific.
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The Washington Post related a story of how the Japanese broad tapeworm affects salmon, and how it could, in turn, affect people who consume the fish.
“In 2012, a Japanese man with a fondness for chilled salmon came down with what physicians described as a ‘watery’ bout of gastrointestinal distress. This was uncomfortable enough, but his illness took a turn for the shocking. The 40-year-old discovered that a meter-long ‘tape-shaped object’ had ’emerged from his anus.'”
Fortunately for the man, he was able to recover quickly and successfully, thanks to oral anti-worm medication. But it marked a classic example of how Diphyllobothrium nihonkaiense – the Japanese broad tapeworm – infects humans, and not just the salmon and other fish they target. Aside from humans, animals such as bears and wolves can also be affected by the parasite.
Outside of the U.S., the Japanese tapeworm has been blamed for about 2,000 illnesses in northeastern Asia, including Japan. And now that it’s been found in four different species of wild Alaskan salmon, the CDC’s team of researchers, which included scientists from the Czech Academy of Sciences and the Alaska Department of Fish and Game, suggest that consumers may want to cook the fish first before eating it.
“Salmon from the American and Asian Pacific coasts and elsewhere pose potential dangers for persons who eat these fish raw.”
In their study, the CDC’s team took 64 examples of wild Alaskan salmon across four types (chinook, coho, pink, and sockeye) in 2013 in search of larvae, and with the help of gene sequencing technology, they concluded that the larvae belongs to the Japanese broad tapeworm, and not fish tapeworm, a parasite that is known to affect North American fish. In one case, a tapeworm was found within the muscles of a Pacific pink salmon, quite close to the fish’s spine.
Alaska Department of Fish and Game pathologist Jayde Ferguson, who was one of the study’s co-authors, spoke to the Alaska Dispatch News, explaining that while there may have been confusion at first between the two types of tapeworm, both fish and Japanese broad tapeworm are essentially similar in terms of how they affect fish. He added that there has been “more and more evidence” of the Japanese tapeworm spreading its reach outside of Asia, but with the reveal of the new study, that has proven that North Americans are “just getting better at identifying it.”
While this new development may suggest that it’s time to avoid the sushi bar and opt for cooked fish in the meantime, Ferguson suggested that things haven’t reached critical mass just yet; Alaskan salmon sold raw on the market is still generally parasite-free for the most part.
“If it was anything that was of concern, increased risk or anything like that from a management standpoint, we would have said something,” he continued. “They’re wild animals — they’re going to have parasites, they’re out in nature.”
[Featured Image by Andrew Burton/Getty Images]