[New data on anisakiasis]

Abstract

Acute anisakiasis is generally due to the third-stage larvae of Anisakis simplex, and occasionally to other anisakidae. Human infection occurs through consumption of raw seafish, and especially herring, hake, black plaice and cod. Patients sensitized by prior consumption of parasitized fish develop, within a few hours, violent abdominal pain and an allergic reaction. Anisakis-induced urticaria is seen in about one in five cases. Preventive measures have reduced the number of cases. In France for example, the number of cases fell four-fold between 1977-1991 and 1992-2005. In 1990 Kasuya [1] reported chronic anisakiasis related to consumption of cooked parasitized fish. Seafish-induced urticaria might be an allergic response to Anisakis larval antigens rather than to the fish itself. Indeed, 11 patients with mackerel-related urticaria all had a positive reaction to Anisakis simplex larval antigen, while none reacted to mackerel antigen. A low-molecular-weight thermostable A. simplex allergen causes chronic urticaria, angioedema and even anaphylactoid reactions. Victims have a genetic predisposition (HLA class II alleles) that is uncommon in France and Germany but frequent in Japan. A number of cases have been observed in Spain, where fish is particularly popular. Immunoblotting shows cross-reactions between antigens of A. simplex and Toxocara canis, nematodes belonging to the same superfamily. At present, the only way to avoid contracting anisakiasis is not to eat raw or even cooked parasitized seafish.