What Is Anisakis?

CDC describes anisakiasis, also called herring worm disease, as a parasitic disease caused by worms that attach to the walls of the esophagus, stomach or intestine. It is most common where eating raw fish is popular, such as Japan, and CDC says that because eating undercooked fish is becoming more common, cases have occurred in the US, Europe, South America and other parts of the world.

CDC lists abdominal pain, nausea, vomiting, abdominal swelling, diarrhea, blood and mucus in stool and mild fever as symptoms, along with allergic reactions such as rashes, itching and, infrequently, anaphylaxis. The FDA's Bad Bug Book says symptoms start 24 hours to 2 weeks after the fish is eaten, and that some people have allergic reactions to dead Anisakis remnants even in cooked or previously frozen fish.

Freezing or cooking kills the worms. FDA seafood guidance says freezing and storing at -4°F (-20°C) or below for 7 days total, or freezing at -31°F (-35°C) or below until solid and then storing at that temperature for 15 hours or at -4°F for 24 hours, is sufficient to kill parasites. The FDA Food Code says fish may be frozen before being served raw as an alternative to cooking, and that candling or other visual inspection is not adequate to avoid parasites in fish that has not been frozen. For cooked fish, the Bad Bug Book points to Food Code guidelines of 145°F for at least 15 seconds, 155°F for fishcakes and 165°F for stuffed fish.