Medical Definition of Anisakiasis

Reviewed on 6/3/2021

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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CDC. "Anisakiasis FAQs." Updated: Nov 21, 2012.