Anisakis simplex induces not only anisakiasis: report on 28 cases of allergy caused by this nematode

Anisakis simplex R., parasitizes several sea-fish and cephalopods. This parasite induces not only anisakiasis but also anaphylactic reactions, as has recently been confirmed. We present 28 patients with immediate hypersensitivity to Anisakis simplex, developed after parasitized fish ingestion. Each case was diagnosed by suggestive anamnesis, skin prick tests with an A. simplex extract, specific IgE detection in serum (CAP System), and histamine release test. The clinical manifestations were urticaria/angioedema in all 28 patients and respiratory arrest in one. Paradoxically, the patients reported tolerance to ingestion of the same kind of fish between and after the allergic episodes. Type 1 hypersensitivity to A. simplex was demonstrated by a positive skin-prick test reaction, specific IgE detection in all cases and positive histamine release in a representative case. Sensitization to the proteins of the fish themselves was ruled out by negative reactions of the same tests in all cases. It was also proven that the allergen/s involved may be resistant to cooking and deep freezing. Hence, anaphylactic reactions may result either from infection or, more frequently, from mere exposure to the allergen. The results confirm that A. simplex can develop IgE-mediated anaphylactic reactions, the clinical severity of which was pronounced in the patients examined. Physicians must take into account that the consumption of parasitized fish may cause severe reactions, even if fish of the same kind is subsequently tolerated. A higher frequency of reactions of this type can be expected in countries where fish is a staple diet.