Anisakis simplex		Contents		Rev 07/26/2012
		Classification		Hosts
		Morphology and Anatomy		Life Cycle
Return to Anisakis Menu		Economic Importance		Damage
		Distribution		Management
Return to Anisakidae Menu		Feeding		References
		Go To Nemaplex Home Page

Rev. 07/26/2012

Classification

Class:    Chromadorea

SubClass: Spiruria

Order:       Ascaridida

Superfamily: Ascaridoidea

Family:         Anisakidae

                          Anisakis simplex

Morphology and Anatomy:

	Infective third-stage juvenile of Anisakis simplex (may reach a length of 2-4 cm.)

Distribution:

Worldwide

Economic Importance:

Anisakiasis has highest incidence in areas where raw fish is eaten (e.g., Japan, Pacific coast of South America, the Netherlands).

Hosts:

Marine mammals such as cetaceans (whales, dolphins) and pinnipeds (seals, sea lions, walruses) are the definitive (primary host for A. simplex; fish are an intermediate host.

Anisakiasis in humans is caused by the accidental ingestion of juveniles of A. simplex in raw or undercooked fish.

Feeding:

Intestinal mucosa

Life Cycle:

Adults are embedded in clusters in the intestinal mucosa of marine mammals. Eggs are passed in the feces of the mammals .  In the water, first-stage juveniles develop in the eggs and molt to the second-stage . The juveniles hatch from the eggs in the second stage and are free-swimming in water .  The juveniles are ingested by crustaceans and develop to third-stage juveniles that are infective to fish and squid when they ingest crustaceans .  In the fish or squid hosts, the juveniles migrate from the intestine to the tissues in the peritoneal cavity and grow up to 3 cm in length.  Upon the host's death, juveniles migrate to the muscle tissues and, through predation by other fish, are transferred to other fish hosts.  Third-stage juveniles persist in fish and squid maintain and are infective to marine mammals (and humans) when their hosts are consumed .  When ingested by mammalian hosts, juveniles 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 juveniles penetrate the gastric and intestinal mucosa, causing the symptoms of anisakiasis.

(adapted from http://www.dpd.cdc.gov/dpdx)

Damage:

Anisakiasis in humans is expressed as violent abdominal pain, nausea, and vomiting within hours after ingesting Anisakis juveniles.  Occasionally the juveniles are coughed up; if they pass into the bowel, a severe eosinophilic granulomatous response may also occur 1 to 2 weeks following infection, with symptoms mimicking Crohn's disease.

Management:

Diagnosis is by gastroscopic examination  or by histopathologic examination of biopsy tissue.

Preferred treatment is surgical or endoscopic removal.  Drugs are available.

Prevention: adequate cooking of fish (60 C) or freezing (-20 C for seven days or -35 C for 15 hours) before ingestion will kill anisakid helminths.

References:

http://www.dpd.cdc.gov/dpdx

Want more information about nematodes? Go to Nemaplex Home Page.