Anisakiosis (Anisakidosis)

Abstract

The term ‘anisakiosis (anisakidosis)’ or ‘anisakiasis’ collectively defines human infections caused by larval anisakids belonging to the nematode family Anisakidae or Raphidascarididae. Anisakis simplex, Anisakis physeteris, and Pseudoteranova decipiens are the three major species causing human anisakiosis. Various kinds of marine fish and cephalopods serve as the second intermediate hosts and the infection source. Ingestion of viable anisakid larvae in the fillet or viscera of these hosts is the primary cause of infection. The parasite does not develop further in humans as they are an accidental host. Clinical anisakiosis develops after the penetration of anisakid larvae into the mucosal wall of the alimentary tract, most frequently the stomach and the small intestine. The affected sites undergo erosion, ulceration, swelling, inflammation, and granuloma formation around the worm. The patients may suffer from acute abdominal pain, indigestion, nausea, vomiting, and in some instances, allergic hypersensitive reactions. Symptoms in gastric anisakiosis often resemble those seen in peptic ulcer or gastric cancer, and symptoms in intestinal anisakiosis resemble those of appendicitis or peritonitis. Treatments include removal of larval worms using a gastroendoscopic clipper or surgical resection of the mucosal tissue surrounding the worm. No confirmed effective anthelmintic drug has been introduced, though albendazole and ivermectin have been tried in vivo and in vitro. Prevention of human anisakiosis can be achieved by careful examination of fish fillet followed by removal of the worms in the restaurant or household kitchen. Immediate freezing of fish and cephalopods just after catching them on fishing boats was reported helpful for prevention of anisakiosis. It is noteworthy that anisakiosis is often associated with strong allergic and hypersensitivity reactions, with symptoms ranging from isolated angioedema to urticaria and life threatening anaphylactic shock.