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Anisakis simplex: a cause of intestinal pseudo-obstruction.

OBJECTIVE
the ingestion of Anisakis simplex larvae may lead to the appearance of gastrointestinal symptoms. However, the number of reported cases of parasitization by Anisakis in Spain is lower than would be expected in a country with the second-highest fish consumption per inhabitant in the world, particularly since fish is often eaten raw or only slightly cooked. We suggest that the incidence of anisakiasis in Spain would be higher if complementary studies were used in all patients suspected of having anisakiasis.


METHODS
we studied 6 patients with a diagnosis of intestinal obstruction who frequently ate fish. Skin prick tests with seafood, inhalant allergen and Anisakis extracts were done. Total and specific IgE against Anisakis larvae were tested with a CAP system radioimmunoassay and immunoblot assays. Oral challenge tests with frozen larvae were also used.


RESULTS
a positive skin prick result and high levels of total and specific IgE were found in all patients. The results of immunoblot assays for IgE did not show a consistent pattern, but a group of several low (14-18 kDa) and intermediate molecular weight antigens (30-50 kDa) were found in all patients. All patients tolerated the oral challenge test well.


CONCLUSIONS
in our patients with intestinal pseudo-obstruction and a history of frequent fish eating, the clinical and laboratory findings were suggestive of parasitization by Anisakis simplex larvae as the cause of the obstruction. Such complementary studies should be used whenever there is a suspicion of anisakiasis. The results of the oral provocation test show that the intake of dead larvae does not induce clinical parasitization.