Results of a study on parasites in fish supports a change to European regulation, according to researchers.

Their work found a low risk of Anisakis larvae infection in fish products from European mariculture activities. Mariculture, a type of aquaculture, involves food production for human consumption in marine environments.

The increasing demand for raw or undercooked fish products, supplied by aquaculture and fisheries, raises concerns about the risk of zoonotic fish parasites, according to the study’s authors. Anisakiasis, which is caused by nematode larvae belonging to Anisakis genus in the marine environment, is considered the main threat to human health.

Current EU rules
European regulation states it is mandatory to apply a freezing treatment of fish products intended to be eaten raw or undercooked but excludes farmed Atlantic salmon. This exemption is based on a European Food Safety Authority (EFSA) opinion from 2010.

Researchers in the journal Eurosurveillance said farmed gilthead seabream, European seabass, turbot and marine rainbow trout should also benefit from the exemption from freezing treatment.

From 2016 to 2018 a survey was undertaken on 6,549 farmed fish including 2,753 gilthead seabream, 2,761 European seabass and 1,035 turbot from 14 farms in Italy, Spain and Greece. These three species represent 95 percent of the EU mariculture production excluding Atlantic salmon.

Two hundred rainbow trout sea-caged in Denmark, 352 seabream and 290 seabass imported in Italy and Spain from other countries were examined as part of the EU funded ParaFishControl project that ended in March 2020. No zoonotic parasites were found in any of these fish.

The finding of a raphidascarid larva in a European seabass from an Italian farm during the study, led to further investigation of the site for this type of parasite which, although not zoonotic, shows similar transmission pathways to Anisakid nematodes. More European seabass runts from the same farm were analyzed and found to be negative, so researchers speculated its presence was accidental.

Surveillance and internal controls
As transmission of anisakid larvae occurs through the chain, the main risks to be monitored are linked to proper management of the fish farm, primarily focusing on implementation of correct feeding protocols and appropriate management of fish size classes.

The approach in the study also sets the groundwork for planning surveillance activities in EU fish farming systems. Diagnostic methods could be used as a tool within a type of Hazard Analysis of Critical Control Point system.

Such a system would help identify any critical points to be monitored during fish farming and document parasitological surveillance for zoonotic parasites along the aquaculture production chain over time. This internal control system should ensure better market prices for fish products with a high safety level and a progressive change to surveillance sampling plans with a lower number of fish to be internally examined, according to the researchers.

With implementation of a voluntary control system at farm level, long-term epidemiological surveillance will be useful to monitor the risk and ensure food safety in European aquaculture products.