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article imageU.S. salmon may carry Japanese tapeworm, CDC scientists say

By Karen Graham     Jan 12, 2017 in Health
Diphyllobothriosis, a human disease caused by tapeworms, is reemerging because of the popularity of eating raw fish. The larvae or plerocercoids of the Japanese broad tapeworm have now been detected in wild salmon netted in Alaskan waters.
The Japanese broad tapeworm, Diphyllobothrium nihonkaiense is the second most common cause of diphyllobothriosis in humans behind the most common broad fish tapeworm, Diphyllobothrium latum, in Japan, according to the CDC.
A) Pink salmon (Oncorhynchus gorbuscha) from Alaska  USA.
A) Pink salmon (Oncorhynchus gorbuscha) from Alaska, USA.
CDC
It is now estimated that over 20 million people are infected with the broad tapeworm, double the number of infections seen in the 1970s. And recent molecular studies have found that the number of cases of diphyllobothriosis caused by D. nihonkaiense has been underestimated,
it was also found that the increasing popularity of eating raw fish, such as sushi or sashimi, is probably responsible for the increased number of imported cases in regions where this infection is not endemic.
B) Plerocercoid of Japanese broad tapeworm (Diphyllobothrium nihonkaiense) (arrow) deep in the muscl...
B) Plerocercoid of Japanese broad tapeworm (Diphyllobothrium nihonkaiense) (arrow) deep in the muscles of the salmon.
CDC
More studies have also identified four species of Pacific salmon as the principal sources of human infection: chum salmon (Oncorhynchus keta), masu salmon (O. masou), pink salmon (O. gorbuscha), and sockeye salmon (O. nerka). These anadromous fish become infected in brackish water along the coast of the North Pacific Ocean.
With the species that can carry the broad tapeworm identified, and previously only thought to be found in salmon in Japan, South Korea and the Pacific coast of Russia, it was surprising that in July 2013, the tapeworm was found in five species of salmon and rainbow trout collected in waters off the coast of Alaska.
C) Live D. nihonka plerocercoid in saline (inset) and scanning electron micrograph after fixation wi...
C) Live D. nihonka plerocercoid in saline (inset) and scanning electron micrograph after fixation with hot water; note the scolex with a long, slit-like bothrium opened anteriorly.
CDC
Scientists used gene sequencing to identify the D. nihonkaiense larvae. The CDC is now warning that unless the problem is not remedied soon, the broad tapeworm could spread globally. They are also warning health care professionals to be aware of a parasitic infection when someone presents with abdominal discomfort, nausea, loose stools and even weight loss.
Because salmon are often transported on ice, the larvae of the broad tapeworm may be able to survive the trip, possibly infecting consumers in Europe, New Zealand, China, and other parts of the U.S. The CDC points out that freezing or cooking the fish will annihilate the tapeworm.
More about Japanese broad tapeworm, Diphyllobothrium nihonkaiense, raw or undercooked salmon, plerocercoids, global spread
 
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