caused by the accidental ingestion of larvae of the nematodes
(roundworms) Anisakis simplex and Pseudoterranova decipiens.
Adult stages of
Anisakis simplex or Pseudoterranova decipiens reside in the
stomach of marine mammals, where they are embedded in the mucosa, in
clusters. Unembryonated eggs produced by adult females are passed in
the feces of marine mammals
The eggs become embryonated in water, and first-stage larvae are formed
in the eggs. The larvae molt, becoming second-stage larvae
and after the larvae hatch from the eggs, they become free-swimming
Larvae released from the eggs are ingested by crustaceans
The ingested larvae develop into third-stage larvae that are infective
to fish and squid
The larvae migrate from the intestine to the tissues in the peritoneal
cavity and grow up to 3 cm in length. Upon the host's death, larvae
migrate to the muscle tissues, and through predation, the larvae are
transferred from fish to fish. Fish and squid maintain third-stage
larvae that are infective to humans and marine mammals
When fish or squid containing third-stage larvae are ingested by marine
mammals, the larvae molt twice and develop into adult worms. The adult
females produce eggs that are shed by marine mammals
Humans become infected by eating raw or undercooked infected marine fish
After ingestion, the anisakid larvae penetrate the gastric and
intestinal mucosa, causing the symptoms of anisakiasis.
higher incidence in areas where raw fish is eaten (e.g., Japan, Pacific
coast of South America, the Netherlands).
Within hours after
ingestion of infected larvae, violent abdominal pain, nausea, and
vomiting may occur. Occasionally the larvae are coughed up. If the
larvae pass into the bowel, a severe eosinophilic granulomatous response
may also occur 1 to 2 weeks following infection, causing symptoms
mimicking Crohn's disease.
Diagnosis can be
made by gastroscopic examination during which the 2 cm larvae are
visualized and removed, or by histopathologic examination of tissue
removed at biopsy or during surgery.
The treatment of
choice is surgical or endoscopic removal.