This article is more than 5 years old. Information may no longer be current.
Researchers find Japanese tapeworm in wild-caught Alaska pink salmon
Click Here to Manage Email Alerts
Researchers who discovered a potentially infectious tapeworm larva in a North American salmon warned that the parasite could potentially sicken people who consume raw fish. The researchers isolated the Japanese broad tapeworm (Diphyllobothrium nihonkaiense) several years ago in a wild-caught Alaska pink salmon.
The tapeworm, commonly found in northeast Asia, is one of several parasites that can cause mostly mild-to-moderate illness in humans who eat fish, according to the CDC. It can grow up to 30 feet long and causes symptoms in humans including abdominal swelling and cramps, weight loss, and anemia, the CDC said.
Human cases, which may be underreported, are on the rise, likely as a result of the popularity of eating raw fish, according to Roman Kuchta, PhD, a researcher in the Institute of Parasitology at the Czech Academy of Sciences, and colleagues.
“For decades, the possible occurrence of the Japanese broad tapeworm on the Pacific coast of North America was ignored, but since 2008, human infection with adult tapeworms and natural infection of carnivores (wolves and bears) with adult tapeworms have been confirmed by use of molecular markers,” Kuchta and colleagues wrote in Emerging Infectious Diseases. “Our main intent is 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.”
To kill parasites, the CDC and FDA recommend cooking fish to an internal temperature of at least 145°F. People who intend to eat raw fish should only eat fish that was previously frozen, the FDA warned. This means freezing fish at −4°F or below for 7 days, at −31°F or below for 15 hours, or at −31°F or below and storing at −4°F or below for 24 hours, according to CDC and FDA guidelines.
Infectious Disease News asked the FDA if fish that are going to be served raw in the United States are required to be frozen before being served.
“If a processor knows, or has reason to know, that a fish with a parasite hazard will not be fully cooked or will be consumed raw, then the processor needs to control the parasite hazard,” the agency said in a statement. “Freezing is the only practical method in current use.”
In July 2013, Kuchta and colleagues examined the musculature and internal organs of 64 wild Pacific salmon from south-central Alaska that they either caught themselves or obtained from local fishermen. The fish included one chinook salmon, one coho salmon, 23 pink salmon, eight rainbow trout, and 31 sockeye salmon.
Among their observations, Kuchta and colleagues discovered a single tapeworm larva deep in the musculature near the spinal cord of a pink salmon caught in Resurrection Creek near Hope, Alaska. Genetic testing proved “unequivocally” that it was a Japanese tapeworm larva, they said.
“This report provides additional evidence that salmon from the Pacific coast of North America may represent a source of human infection,” Kuchta and colleagues wrote. “Because Pacific salmon are frequently exported unfrozen, on ice, plerocercoids 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.” – by Gerard Gallagher
Disclosures: The researchers report no relevant financial disclosures.
Click Here to Manage Email Alerts