Next Page

Clinical Characteristics

The infection seems to be more common in males (3:1) and in the 20 to 50 years group. It is found where fish is eaten raw (Japanese "sashimi, sushi or sunomono" or Peruvian "ceviche"), insufficiently salted or pickled (Dutch or German "green herring") or undercooked (nouvelle cuisine), leading to development of gastric or intestinal anisakiasis. Localization of the "tumor" caused by the worm is more common in the stomach in Japan, whereas in the Netherlands and Europe the majority of lesions are in the small bowel. It has been speculated that these anatomical preferences are due to variations in the species of the parasite and to different local eating habits. The species of anisakine parasites varies greatly between the marine zones according to the distribution of the intermediate and final hosts, and there is a different pattern of parasitism in the fish consumed in certain areas. Some fish contain larvae only in their viscera, while others, like the Pacific salmon and true herring, often harbor larvae in their flesh. There is a high level of parasitism in some fish species used to prepare delicacies such as sushi and sashimi, regularly eaten by 20 to 40 year-old male Japanese professionals and office workers, in whom there is an extremely high incidence of anisakiasis. The preponderance of gastric anisakiasis in Japan may also be due to low levels of hydrochloric acid in their stomachs, as well as their custom of eating raw seafood in small pieces accompanied by alcohol, all of which may influence the site of penetration of the worm.

Many patients with gastric anisakiasis will have no clinical complaints. In others, symptoms will begin 1 to 24 hours after eating infected seafood, and may resemble those of a peptic ulcer or neoplasm, with complaints of severe epigastric pain, nausea and vomiting, and occasionally diarrhea. The peripheral blood may show a moderate eosinophilia. Some patients may develop a milder, more chronic illness with loss of appetite and weight, and recurrent epigastric pain, which can persist for years.

When the infection is predominantly in the small bowel, symptoms may have a gradual or sudden onset after an incubation period of one day to a few weeks. There may be violent colicky abdominal pain, nausea, vomiting, diarrhea, bloating and a low fever. Abdominal tenderness is common and is often localized to the right lower quadrant: acute appendicitis is often suspected. The infection may become chronic and protracted, and cases lasting many years have been reported. Such patients complain of abdominal distention and transient attacks of crampy lower abdominal pain with intermittent slimy diarrhea and weight loss. Blood within the stool is an almost constant finding. For those undiagnosed patients who undergo laparotomy, the preoperative diagnosis is usually that of appendicitis or Crohn's disease. At surgery the infected segment is found to be edematous, indurated and congested, and there is usually a moderate amount of peritoneal fluid. Occasionally a perforation, or even a thread-like worm may be recognized.

There have been a few patients, chiefly from North America, who presented with tingling in the throat and in whom Pseudoterranova larvae have been expectorated or vomited or removed from the orophaynx a few days after eating a suspicious fish meal. Occasional patients have also been reported with generalized urticaria, allergic polyarthritis and eosinophilic pleural effusion.

Back to the Table of Contents

Copyright: Palmer and Reeder

Tropical Medicine Mission Index of Diseases About Tropical Medicine Tropical Medicine Home Page Tropical Medicine Staff