Parasites are common in wild fish from the sea. This is particularly true for the larvae of certain parasitic nematodes. The most important species in our waters is Anisakis simplex, which may cause acute gastrointestinal illness if accidentally eaten alive. However, parasitic nematodes will die at freezing, frying, boiling, or strong salting over an extended period. In Norway, farmed Atlantic salmon (Salmo salar) has for several years been exempted from the so-called freezing requirement, since the risk of farmed salmon containing nematodes was regarded negligible. This is because the parasitic nematode life-cycle is broken when the salmon is exclusively fed heat-treated dry feed. This exemption from the freezing requirement may also be applicable to other farmed species, where it can be documented that there is no risk of attaining parasitic nematodes if the fish is eaten raw. The Norwegian Food safety authority (NFSA) wants to include this freezing exemption in national regulations, and include other farmed species, where documentation of the absence of Anisakis is satisfactory. Therefore, there is need for update documentation, similar to the documentation for salmon, showing that the fillets of farmed rainbow trout do not pose any health hazard with regards to the presence of nematodes.
The main objective of the project is to establish the epidemiological baseline concerning the occurrence of Anisakis in Norwegian farmed rainbow trout, as the basis for assessment of the exemption from the freezing requirement before raw consumption. In addition to being an important contribution to the revision of existing regulations, the project will provide increased knowledge of important factors affecting the occurrence of Anisakis in Norwegian cultured rainbow trout.