Scared of sushi? The Anisakis worm is a parasite that can cause nasty infections in humans who enjoy eating raw fish. It is 2 cm long and is sometimes coughed up after ingesting it in raw or undercooked fish.
Type of Microbe:Parasitic nematode (roundworm)
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How It Spreads
You’re at risk if you eat raw or undercooked seafood. The parasite is found frequently in cod, haddock, fluke, Pacific salmon, herring, flounder, and monkfish.
The US reports fewer than 10 diagnosed cases each year. In Japan, where raw fish is an integral part of the Japanese diet, more than 1000 cases have been reported each year.
Symptoms and Diagnosis
Penetration of the worm into intestinal tissues causes a local inflammatory immune response that results in the symptoms of anisakiasis. Common symptoms include:
After penetrating the intestine, the worm attracts white blood cells called eosinophils and macrophages and forms a mass of immune tissues called a granuloma.
Human infection is a dead end in the parasite’s life cycle. The worms are usually eliminated or expelled from the intestines within 3 weeks of infection.
Treatment and Prevention
Treatment is surgical or endoscopic removal of the parasites.
The FDA has provided several guidelines for retailers who sell fish intended to be eaten raw. These guidelines include freezing the fish to -31°F for 15 hours or -4°F for 7 days to kill parasites and physical examination known as “candling” for the presence of worms.
Complications
If the worm is not coughed up or vomited out, it may penetrate the intestinal tissues, causing a severe immune response that resembles appendicitis orCrohn’s disease.
Frequently Asked Questions
Symptoms of anisakiasis can include violent abdominal pain, nausea, and vomiting. When the Anisakis worm enters intestinal tissues, it triggers an inflammatory immune response in the body, resulting in these symptoms.
Yes, freezing fish for certain lengths of time should kill its parasites. The Food and Drug Administration (FDA) provides guidelines on how to eliminate parasites for retailers who sell raw fish.
3 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.European Academy of Allergy and Clinical Immunology.Anisakis.Centers for Disease Control and Prevention.Anisakiasis.Centers for Disease Control and Prevention.Anisakiasis FAQs.
3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.European Academy of Allergy and Clinical Immunology.Anisakis.Centers for Disease Control and Prevention.Anisakiasis.Centers for Disease Control and Prevention.Anisakiasis FAQs.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
European Academy of Allergy and Clinical Immunology.Anisakis.Centers for Disease Control and Prevention.Anisakiasis.Centers for Disease Control and Prevention.Anisakiasis FAQs.
European Academy of Allergy and Clinical Immunology.Anisakis.
Centers for Disease Control and Prevention.Anisakiasis.
Centers for Disease Control and Prevention.Anisakiasis FAQs.
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