New Study Confirms Presence of Tapeworm in Wild Salmon

Larvae of the Japanese broad tapeworm, which is associated with tapeworm infections in humans, has been detected in wild salmon in Southcentral Alaska, but a state fisheries pathologist says this is no reason for alarm.

“It’s a common thing,” said Jayde Ferguson, a pathologist with the Alaska Department of Fish and Game, who assisted fisheries scientists from the Czech Republic in their study, which was published in the February edition of the Centers for Disease Control and Prevention’s Emerging Infectious Diseases report.

The Alaska Seafood Marketing Institute responded quickly to the report about the presence of tapeworm infections in wild Alaska salmon, saying that Alaska salmon is among the highest quality seafood and safe for consumer consumption.

“All commercially harvested Alaska seafood, which accounts for more than 60 percent of all the seafood harvested in the United States, is processed in accordance with strict Food and Drug Administration regulations, including parasite controls,” ASMI said.

FDA guidelines dictate that seafood be frozen to minus-4 degrees Fahrenheit or below for seven days if it is to be consumed raw for food safety reasons. Salmon that has not been properly frozen should be cooked thoroughly to an internal temperature of 140 degrees Fahrenheit before consumption. For any raw or semi-raw preparations, ASMI always recommends using properly frozen seafood.

The tapeworm has been here for thousands of years, but identifying these worms is very challenging,” Ferguson said in an interview Jan. 12.

While people can get diphyllobothriosis (tapeworm infections) from infected fish, they can easily be avoided, he said.

An online booklet produced by ADF&G ( notes that cooking fish to at least 140 degrees Fahrenheit at least five minutes, or freezing it for at least 60 hours at minus-4 degrees will kill parasitic worms. Details on tapeworm are on pages 60-61. The same guidance should be followed before feeding these salmon to dogs and cats, he said.

Since ADF&G doesn’t have baseline data on this subject, the prevalence of this parasite in Alaska’s salmon is unknown, Ferguson said.

America may represent a source of human infection,” the Czech report said. “Because Pacific salmon are frequently exported unfrozen, on ice, plerocercoids (the last larval stage of this flatworm) may survive transport and cause human infections in areas where they are not endemic, such as China, Europe, New Zealand and middle and eastern United States.

“For more effective control of this human foodborne parasite detection of the sources of human infection (i.e. host associations) and critical revision of the current knowledge of the distribution and transmission patterns of individual human-infecting tapeworms are needed.”