Infectious disease experts have identified a parasitic Japanese broad tapeworm in around 2,000 reported illnesses in Japan and parts of northeastern Asia.
The first case of an infection from the parasite known as Diphyllobothrium nihonkaiense occurred in 2008 in North America. The parasite primarily grows inside fish, but is able to infect humans, wolves, and bears.
Though the worms had previously been found in wild Asian fish, a new study in the Centers for Disease Control and Prevention’s (CDC) journal, Emerging Infectious Diseases, the tapeworm has been discovered in North American waters near the Alaskan coast.
Researchers who conducted the study—tapeworm experts from the Czech Academy of Sciences and biologists at the Alaska Department of Fish and Game—found that “salmon from the American and Asian Pacific coasts and elsewhere pose potential dangers for persons who eat these fish raw.”
The team used a newly developed molecular technique to identify the Japanese species of tapeworm larvae using microscopes to examine several types of wild Alaskan salmon: chinook, coho, pink and sockeye salmon, as well as rainbow trout.
They found a Japanese broad tapeworm nestled near the spine of a Pacific pink salmon, deep in its muscle tissue.
Though the vast majority of raw salmon available to consumers does not pose the risk of parasitic infection, raw foods in general tend to bring more risk than cooked food.
“If it was anything that was of concern, increased risk or anything like that from a management standpoint, we would have said something,” Jayde Ferguson—a Department of Fish and Game ecologist and study author—told Alaska Dispatch News.
He said that the wild fish represented in the study pose a higher risk of parasitic infection.
“They’re going to have parasites, they’re out in nature,” he said.
The researchers assert that the aim of the study is not to cause fear in consumers, but to “alert parasitologists and medical doctors about the potential danger of human infection with this long tapeworm resulting from consumption of infected salmon imported (on ice) from the Pacific coast of North America and elsewhere.”
The likelihood of becoming infected with tapeworms in the U.S. is very low. The CDC added that most Japanese broad tapeworm infections show very few symptoms and thus, go unnoticed.
