A study published by the U.S. Centers for Disease Control reports the discovery of Japanese broad tapeworm in samples of wild Alaska salmon, but state officials say adherence to strict federal standards assures the safety of commercially caught fish.
The study, which appears in the February issue of the journal Emerging Infectious Diseases, was published by the U.S. Centers for Disease Control and Prevention.
The tapeworm, Diphylloborthrium nihonkaiense, was detected by a group of scientists from the Czech Republic, in the musculature of wild pink salmon from Southcentral Alaska.
This particular tapeworm is common in Pacific salmon and has been around for thousands of years, but identifying these worms is very challenging, said Jayde Ferguson, a fisheries pathologist with the Alaska Department of Fish and Game.
“There is no need for an alarm. It’s a common thing.”
While people can get diphyllobothriosis (tapeworm infections) from infected fish, such infections can easily be avoided, he said.
The study, supported by Czechoslovakian research groups, examined 64 wild Pacific salmon from Southcentral Alaska, including one king, one coho, 23 pink, eight rainbow trout and 31 red salmon. Researchers filleted the musculature of each fish to narrow slices, and internal organs were observed under a magnifying glass.
The Czech researchers detected the presence of several morphotypes of diphyllobothriid plerocercoids. They said their work provided additional evidence that salmon from the Pacific coast of North American may represent a source of human infection.
“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.”
The Alaska Seafood Marketing Institute, responding to news of the report, promptly issued a statement noting that all commercially harvested seafood in Alaska is processed in accordance with strict U.S. Food and Drug Administration regulations, including parasite controls.
“These regulations specifically guard against potential harm to ensure that eating both salmon sushi and fully cooked salmon can be safely enjoyed,” ASMI said.
“The Alaska seafood industry adheres to standards that provide safe seafood products,” said Ted Meyers, ADF&G’s principal fish pathologist. “The Alaska Department of Fish and Game works closely with the Alaska seafood industry to ensure that healthy fish are available for consumers.”
FDA guidelines state that seafood should be frozen to minus-4 degrees Fahrenheit or below for seven days if it is to be consumed raw, and that salmon that has not been properly frozen should be cooked thoroughly to an internal temperature of 140 degrees Fahrenheit before consumption.
ADF&G has produced an online booklet (https://www.adfg.alaska.gov/static/species/disease/pdfs/fish_disease_book.pdf) with information about various diseases in fish and how to avoid them.
The booklet 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, Ferguson said.
