In the stage which infects fish, Anisakis species are found in a distinctive "watch-spring coil" shape. They are roughly 2 cm long when uncoiled. When in the final host, anisakids are longer, thicker, and more sturdy, to deal with the hazardous environment of a mammalian gut. Health implications
Anisakids pose a risk to human health through intestinal infection with worms from the eating of underprocessed fish, and through allergic reactions to chemicals left by the worms in fish flesh. Anisakiasis
Anisakiasis is a human parasitic infection of the gastrointestinal tract caused by the consumption of raw or undercooked seafood containing larvae of the nematode Anisakis simplex. The first case of human infection by a member of the family Anisakidae was reported in the Netherlands by Van Thiel, who described the presence of a marine nematode in a patient suffering from acute abdominal pain. It is frequently reported in areas of the world where fish is consumed raw, lightly pickled, or salted. The areas of highest prevalence are Scandinavia (from cod livers), Japan (after eating sashimi), the Netherlands (by eating infected fermented herrings (maatjes)), Spain (from eating anchovies and other fish marinated in escabeche), and along the Pacific coast of South America (from eating ceviche). The frequency in the United States is unknown, because the disease is not reportable and can go undetected or be mistaken for other illnesses. Anisakiasis was first recognized in the 1960s. During the 1970s, about 10 cases per year were reported in the literature.
Similar parasites
Cod or seal worm Pseudoterranova (Phocanema, Terranova) decipiens 
Contracaecum spp. Hysterothylacium (Thynnascaris) spp. See also
List of parasites of humans

References
External links

CDC page on Anisakiasis
Endoscopy video of Anisakiasis
Sushi, nemotodes and allergies in Canada