Medical Definition of Anisakiasis

  • Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

Reviewed on 9/7/2018

Anisakiasis: a parasitic disease caused by nematodes (worms) that attach to the wall of the esophagus, stomach, or intestine. Anisakiasis is also known as herring worm disease. The parasite is transmitted to human when eating raw or undercooked fish or squid. Symptoms of anisakiasis include nausea, vomiting, abdominal distention and pain, diarrhea, blood and/or mucus in the stool, and fever. Allergic reactions can also occur.

The transmission of anisakiasis begins when infected marine mammals defecate into sea water and release eggs of the parasite. These mature into larvae and are eaten by crustaceans. In turn, the crustaceans are consumed by fish or squid, so that human who eat raw fish risk ingesting the larvae. In the human host, the larvae pass into the gastrointestinal tract, eventually dying and forming a mass there.

It is possible to feel a tingling sensation after or while eating raw or undercooked fish or squid due to the worm moving. In these cases it is sometimes possible to remove the worm manually from the mouth or cough up the worm. Vomiting can also be a symptom after consuming the parasites, and this may also expel the worm.

Anisakiasis is not transmitted from person to person. Prevention of the condition involves avoiding eating raw or undercooked fish or squid.


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Reviewed on 9/7/2018
CDC. "Anisakiasis FAQs." Updated: Nov 21, 2012.