An Introduction to Anisakiasis

Anisakiasis is an intestinal nematode, meaning that it is a nonsegmented roundworm that invades the human gut. The Nematodes belong to the phylum Nematoda and are relatively advanced parasites; most are free living, have complete digestive systems and are also sexually dimorphic. The parasite was first discovered in the Netherlands after a nematode was surgically removed from the mucus membrane of a patient’s small intestine. Humans become infected by consuming raw or undercooked fish containing 3rd-stage larva. Humans can also have allergic reactions to chemicals produced by the worm that remain in the fish flesh. Crustaceans and small fish are reservoirs for this parasite. Larger fish (such as herring, mackerel and salmon) vector the larva to humans. The larva develop into adult worms inside one’s stomach or small intestine. The parasite only fully matures inside a marine mammal’s gastrointestinal tract. Symptoms include abdominal pain and nausea. Onset of illness is 1 to 5 days after consuming contaminated seafood. The majority of human infections are reported in Japan (from sushi and sashimi consumption) and the Netherlands (from pickled herring consumption). Diagnosis is made upon history of exposure and sometimes gastroscopy or surgery. Anisakasis is not lethal and does not usually produce acute symptoms, so no treatment is necessary. However, 400 mg of Albendazole, twice daily for 21 days is curative.

Agent (Classification and Taxonomy)

Kingdom: Animalia
Phylum: Nematoda
Class: Secernentea
Order: Ascaridida
Family: Anisakidae
Genus: Anisakis
Species: A. pegreffii, A. physeteris, A. schupakovi, A. simplex, A. typical, A. ziphidarum