Morphology

As a nematode, the Anisakids are round, unsegmented worms. In serious cases of Anisakiasis the thin, cylindrical, nonsegmented worm may actually be surgically removed. For a parasite, Anisakids are relatively developed. They have both an oral and anal opening and the male and female sexes are different in appearance. The mouth of the nematode has evolved projections intended for feeding and sensation. The epidermis of the parasite has notable excretory glands.

Larva can grow to be a length of 50mm with a 1mm to 2 mm diameter. They usually coil in a characteristic watch-spring shape. In the definite host (a marine mammal or human), the worms are longer and thicker. This allows them to survive within the species’ gastrointestinal tract.

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The worm invades the ileum.

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A Korean patient presents an adult worm.