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Pathology of Anisakiasis

Dr Sampurna Roy MD             





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.

Image1 ; Image2 ; Image3 ; Image4 (Dr Y Tsutsumi)


Further reading:

Low immunoglobulin E response in gastroallergic anisakiasis could be associated with impaired expulsion of larvae.

Different serum cytokine levels in chronic vs. acute Anisakis simplex sensitization-associated urticaria.

Two Cases of Gastric Anisakiasis for which Oral Administration of a Medicine Containing Wood Creosote (Seirogan) was Effective.

Anisakis simplex s.l. parasitization in mackerel (Scomber japonicus) caught in the North of Morocco - prevalence and analysis of risk factors.

Distribution of Anisakis species larvae from fishes of the Japanese waters.

Ani s 10, a new Anisakis simplex allergen: cloning and heterologous expression.

Anisakis simplex-induced anaphylaxis.

Small bowel anisakiosis: a report of two cases.





Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)






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