Scientific Opinion on risk assessment of parasites in fishery products

Human fishery product-borne parasitic diseases are caused by cestodes, trematodes and nematodes and are caused by infection following ingestion of viable parasites, or as allergic (hypersensitivity) reactions against parasite antigens. For allergy, the only parasite in fishery products implicated is the nematode Anisakis simplex, and sensitisation occurs via infection by live larvae. Once sensitised, response to nematode allergens can be highly aggressive and generate severe disease. In a sensitised individual, infection can provoke a concurrent A. simplex allergic episode or can be elicited by exposure to allergen alone from killed parasite: the relative epidemiological impact for each is unknown. Allergy to A. simplex is relatively common in some regions in Spain but rarely reported in other parts of Europe. Prevention of sensitisation is most likely to be effective by control of A. simplex infection. There is more information on the resistance to physical and chemical treatments by A. simplex than for other fishery parasites, and the properties of other parasites are likely to be similar. Many traditional marinating and cold smoking methods are not sufficient to kill A. simplex and freezing or heat treatments remain the most effective processes guaranteeing killing. All wild caught seawater and freshwater fish are must be considered at risk of containing any viable parasites of human health concern if these products are to be eaten raw or almost raw. For wild-catch fish, no sea fishing grounds can be considered free of A. simplex. For farmed Atlantic salmon reared in floating cages or onshore tanks and fed on compound feedstuffs however, the current risk of infection with anisakids is negligible. Apart from farmed Atlantic salmon, sufficient monitoring data are not available for any other farmed fish therefore it is not possible to identify which fish species do not present a health hazard with respect to the presence of parasites.

© European Food Safety Authority, 2010

Following a request from the European Commission, the Panel on Biological Hazards was asked to deliver a scientific opinion on food safety related to parasites in fishery products.

In particular EFSA was asked to: assess the food safety concerns due to possible allergic reactions in consumers to parasites that may be present in fishery products; evaluate alternative treatments for killing viable parasites in fishery products and evaluate their effectiveness compared to the freezing method described in the hygiene regulations; set criteria, if any, for when products are eaten raw almost raw or cold smoked from fishing grounds for wild catch and from aquaculture do not present a health hazard with regard to the presence of parasites, and an assessment of available documentation for farmed Atlantic salmon

EFSA concluded that human fishery product-borne parasitic diseases primarily include those caused by cestodes, trematodes and nematodes. These diseases are either caused by an infection following ingestion of viable parasites, or as an allergic (hypersensitivity) reaction against parasite antigens. The only parasite in fishery products that is implicated in allergic reaction is the nematode Anisakis simplex and that the primary initiator of the different forms of allergy is via infection by live larvae. Once sensitisation has occurred, response to nematode allergens can be highly aggressive and generate severe allergic disease. Some authors have shown that an infection can provoke a concurrent allergic episode in a sensitised individual, and claim this is the principal mechanism for disease. However, others consider that allergic episodes can not only be elicited by infection, but also by exposure to allergen remaining in food with no viable larvae. The relative epidemiological impact for each route of provoking an allergic episode is unknown. However there is general agreement that consumption of fishery products containing viable A. simplex larvae presents a greater risk for allergy than consumption of fishery products containing non-viable parasites. The different forms of allergy to A. simplex are relatively common in some regions in Spain but rarely reported in other parts of Europe.

EFSA concluded that there is more information on the resistance to physical and chemical treatments by A. simplex than for other fishery parasites. The properties of A. simplex are likely to be similar to that of other multicellular parasites (although trematode metacercariae are considerably more heat resistant). Freezing or heat treatments remain the most effective processes guaranteeing the killing of parasitic larvae, under well defined conditions. Treatments which provide an equivalent level of protection as freezing (-20ºC for not less than 24 hours) for the killing of A. simplex larvae include freezing at -35ºC for at least 15 hours or at -15°C for at least 96 hours, at the core of the fishery products and heat treatment at >60ºC for at least 1 minute. Many traditional marinating and cold smoking methods are not sufficient to kill A. simplex larvae.

All wild caught seawater and freshwater fish must be considered at risk of containing any viable parasites of human health concern if these products are to be eaten raw or almost raw. For wild catch fish, no sea fishing grounds can be considered free of A. simplex larvae. For farmed Atlantic salmon, if reared in floating cages or onshore tanks and fed on compound feedstuffs, which are unlikely to contain live parasites, the risk of infection with larval anisakids is negligible unless changes in farming practices occur. Apart from farmed Atlantic salmon, sufficient monitoring data are not available for any other farmed fish therefore it is not possible to identify which farmed fish species do not present a health hazard with respect to the presence of parasites.

EFSA recommends that co-ordinated studies to improve surveillance and diagnostic awareness of allergic reactions to parasites in fishery products should be implemented, and encourage epidemiological studies on a European scale to assessing the impact of A. simplex parasitized fish on human associated disease, including all allergic forms.

EFSA recommends that research should be improved on:

• The infectivity as well as inactivation of parasites in fishery products in relation to treatments, host fish species, and effects of passage through different hosts
• The effects of different farming practices on the prevalence of anisakids in aquaculture if products are to be consumed raw or almost raw.
• The collection of systematic data on the complete life cycle, geographical and seasonal distribution, prevalence, intensity, and anatomical location of parasites of public health importance in wild caught fishery products.
   

Fishery products, Anisakis, allergy, farmed Atlantic salmon