Prevalence of and risk factors for IgE sensitization to Anisakis simplex in a Spanish population

Background: The number of allergic reactions to A. simplex reported in Spai n has increased dramatically in the last decade. Nevertheless, there have b een no studies of the prevalence of and possible risk factors for IgE sensi tization to this parasite, possibly because suitably specific diagnostic me thods have only recently become available. The objective was to investigate the prevalence of and risk factors for IgE sensitization to A. simplex in Galicia, a region of northwestern Spain with a population of about 3 millio n and high average fish consumption (78.5 g/person per day). Methods: The study was performed with a random sample of 2801 healthy blood donors distributed in 53 geographic areas, proportional to the density of donors. IgE sensitization to A. simplex was tested by a capture ELISA metho d that has proved to be the most specific method currently available. Results: The results showed a total of only 12 positive subjects, of whom f ive also showed IgG1 sensitization. All positive subjects and 101 randomly selected seronegative subjects were then included in a case-control study o f risk factors for sensitization to A. simplex, based on a telephone interv iew about fish consumption (especially raw and undercooked fish). All serop ositive subjects (but only 25% of seronegative subjects) reported consumpti on of undercooked fish or homemade raw-fish products. Conclusions: Our results strongly suggest that sensitization to A. simplex is caused only by live larvae, and not by allergens contained in fish tissu es, and that ingestion of homemade boquerones (anchovies [Engraulis encrasi cholus] in vinegar), and to a much lesser extent of undercooked fish, are t he main risk factors for IgE sensitization to Anisakis in this region.