Anisakis simplex: from Obscure Infectious Worm to Inducer of Immune Hypersensitivity

Abstract

SUMMARY Infection of humans with the nematode worm parasite Anisakis simplex was first described in the 1960s in association with the consumption of raw or undercooked fish. During the 1990s it was realized that even the ingestion of dead worms in food fish can cause severe hypersensitivity reactions, that these may be more prevalent than infection itself, and that this outcome could be associated with food preparations previously considered safe. Not only may allergic symptoms arise from infection by the parasites (“gastroallergic anisakiasis”), but true anaphylactic reactions can also occur following exposure to allergens from dead worms by food-borne, airborne, or skin contact routes. This review discusses A. simplex pathogenesis in humans, covering immune hypersensitivity reactions both in the context of a living infection and in terms of exposure to its allergens by other routes. Over the last 20 years, several studies have concentrated on A. simplex antigen characterization and innate as well as adaptive immune response to this parasite. Molecular characterization of Anisakis allergens and isolation of their encoding cDNAs is now an active field of research that should provide improved diagnostic tools in addition to tools with which to enhance our understanding of pathogenesis and controversial aspects of A. simplex allergy. We also discuss the potential relevance of parasite products such as allergens, proteinases, and proteinase inhibitors and the activation of basophils, eosinophils, and mast cells in the induction of A. simplex-related immune hypersensitivity states induced by exposure to the parasite, dead or alive.

Anisakid larva parasitizing Plagioscion squamosissimus in Marajó Bay and Tapajós River, state of Pará, Brazil

“…Therefore, attention paid towards consumption of raw fish in exotic dishes needs to be increased, because such consumption can increase the risk of acquiring anisakiasis. It is also important to draw attention to this species, given that it can cause gastrointestinal disorders and allergic reactions even if consumed cooked (AUDICANA & KENNEDY, 2008). …”

Cross-sectional study of serum reactivity to Anisakis simplex in healthy adults in Niterói, Brazil

“…Most cases are reported in Japan, where consumption of raw fish is traditional. However, the number of new cases worldwide has risen steadily over the last decades (Audicana and Kennedy 2008).…”

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“…There is lack of fast and reliable techniques for identification of parasites in fish products. Audicana and Kennedy (2008) pointed out that unfortunately, even dead A. simplex can cause allergic reactions to humans due to allergens left in the food. Therefore, the current preventive or control measures for a complete safety from A. simplex are not efficient.…”

“…Therefore, the current preventive or control measures for a complete safety from A. simplex are not efficient. Several studies have concentrated on A. simplex antigen characterization and innate as well as adaptive immune response to this parasite over the last 20 years (Audicana and Kennedy, 2008). Aquaculture could have advantages over extractive fishing in supplying fish guaranteed to be free from A. simplex and related parasites.…”