Infectious Disease Online
Pathology of Anisakiasis
Anisakiasis is caused by the accidental ingestion of larvae of the nematodes (roundworms) Anisakis simplex and Pseudoterranova decipiens.
[ Anisakiasis caused by Anisakis simplex - Herringworm disease ; Whaleworm disease. Anisakiasis caused by Pseudoterranova decipiens - Codworm disease; Sealworm disease.]
This parasitic infection should be considered in the differential diagnosis of acute abdominal syndromes and eosinophilic infiltrates of the stomach, small intestine, colon, omentum, and mesentery, especially with a history of raw marine fish consumption.
Aniskiasis is contracted when inadequately cooked fish containing these nematode larvae are eaten.
Popular foods containing viable larvae are pickled herring in Scandinavian countries, sushi or sashimi in Japan, and cord, flounder, and tuna from the east coast of the United States.
Nematodes causing anisakiasis have a marine mammal as the definitive host.
In humans the larvae penetrate the wall of the throat, stomach, intestine or colon.
Intestinal discomfort begins a few hours after eating the fish.
Larvae are released from the muscle of the fish, penetrate the gastric or intestinal mucosa, or become attached in the throat without invasion of tissue.
Infection is diagnosed after surgical intervention for intestinal obstruction or peritonitis, which is caused by necrotizing, eosinophilic, granulomatous inflammation.
Worms in the throat or stomach are frequently vomited or coughed up, and a common clinical presentation is a wriggling sensation in the throat, with larvae appearing in the mouth of an alarmed patient.
Intestinal anisakiasis clinically resembles appendicitis, with right lower quadrant pain, nausea, and vomiting.
Continued migration to omentum or mesentery is common.
Worms lodge in and thicken the gastric or bowel wall.
The identification of larvae provides the diagnosis.
Infections of the small intestine, caecum, or colon are usually not diagnosed before exploratory laparotomy.
Removal of worms relieves the symptoms.
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