Researchers have discovered that a tapeworm typically found in salmon in northeast Asia now also exists in some salmon caught in the United States.
The Japanese broad tapeworm, or Diphyllobothrium nihonkaiense, was found in several types of salmon off of Alaska’s Pacific Coast. Broad tapeworms can grow up to 30 feet long, but infections are not common, and when they do occur, most have no symptoms, according to the Centers for Disease Control and Prevention (CDC). However, symptoms can include stomachaches, diarrhea, vomiting and weight loss. Infection can also cause vitamin B12 deficiency, which can lead to anemia.
Researchers examined 64 wild Pacific salmon, including rainbow trout and Chinook, pink and sockeye salmon, according to a report in the CDC journal Emerging Infectious Diseases. Evidence of broad tapeworm larvae were found in several fish, and a half-inch-long tapeworm was found in a pink salmon. The researchers said they reported their findings primarily to alert parasitologists and physicians about the potential danger of human infection.
Eating any raw or undercooked fish comes with a risk of food poisoning. However, parasites, including broad tapeworms, can be killed with proper storage and preparation.
So, what are experts saying? “If you weren’t worried about eating salmon before, you shouldn’t be worried now,” says Matt Grieser, RD, a clinical dietitian at Indiana University Health. “Just use caution when preparing your fish so it’s safe.” Salmon continues to be a healthy source of protein, he says, and it is high in omega-3 fatty acids, which help lower cholesterol and boost brain function.
To kill parasites in fish, the U.S. Food and Drug Administration (FDA) recommends consumers do one of the following:
- Cook fish to an internal temperature of at least 145° F.
- Freeze fish at -4°F or below for seven days.
- Freeze fish at -31°F or below until solid, then store at -31°F or below for 15 hours.
- Freeze fish at -31°F or below until solid and then store at -4°F or below for 24 hours.
Freezing salmon properly before sashimi or sushi preparation is particularly important because salmon is often transported on ice but not frozen. Additionally, pregnant women and people with weaker immune systems, such as those undergoing chemotherapy, should not eat raw fish because of the risk of foodborne illness, commonly known as food poisoning. Elderly people may also want to take special precautions. By age 75, many adults have a weakened immune system and are at increased risk from foodborne illness, according to the FDA.
While reputable restaurants should be following the FDA recommendations on freezing fish, consumers can always ask staff where their salmon came from to gain clarity. To learn more about buying and preparing seafood safely, visit the FDA’s consumer safety webpage.
-- By Melanie Padgett Powers