Scientists in Europe have updated the knowledge around parasites in fish based on available surveillance data.

The European Food Safety Authority (EFSA) scientific opinion also evaluated methods for detecting and killing parasites in fish.

European data indicates that many species of farmed fish are free from parasites that can infect humans. These include Atlantic salmon, rainbow trout, gilthead seabream, turbot, meagre, Atlantic halibut, carp, and European catfish.  

However, Anisakis pegreffii, Anisakis simplex and Cryptocotyle lingua were found in European seabass, Atlantic bluefin tuna and/or cod, and Pseudamphistomum truncatum and Paracoenogonimus ovatus in tench, produced in open offshore cages or flow-through ponds or tanks.

Situation in Europe
Eleven foodborne outbreaks caused by Anisakis occured in the EU from 2010 to 2022. In 2020, there were two outbreaks, both reported by Spain, involving six people.

From 2010 to 2023, there were 544 reports of infected fishery products reported by 21 EU member states to the Rapid alert System for Food and Feed (RASFF). Italy had the most with 274 reports. Origin of products mainly included Spain, Morocco, and France. Anisakis was the parasite reported in the majority of notifications.

Experts said it was almost certain that fish produced in closed recirculating aquaculture systems or flow-through facilities with filtered water intake and only fed heat-treated feed are free of parasites.

The offshore location of salmon farms may result in increased exposure of the fish to anisakids as they are situated close to marine mammals’ migration routes and habitats. Aquaculture that relies on the capture of juvenile wild fish for subsequent growing and fattening in captivity, as used for Atlantic bluefin tuna in Europe, also potentially facilitates exposure of fish to parasites.

Scientists said more data was needed to estimate the prevalence of parasites in seleced fish species, farming systems, and production areas in Europe.

The European Commission had asked EFSA to updat certain aspects of a 2010 scientific opinion on the risk assessment of parasites in fish products.

Currently, the relationship between survival of the larvae, after a given treatment, and their infection capacity in humans is unclear, and as stated in the past opinion, a precautionary principle is adopted, meaning all larvae should be dead, which gives a higher margin of safety.

Detecting and killing parasites
Ecological drivers of infection of fish with parasites include temperature, salinity and oceanographic conditions; the fishing ground; fish length and size and part of the fish that is infected. Climate change may have an impact because of rising water temperature. People are also consuming raw or undercooked foods more often.

Freezing and heating continue to be the most efficient methods to kill parasites in fishery products. High-pressure processing may be suitable for some products. Pulsed electric field is a promising technology although further development is needed but ultrasound treatments were not effective.

For freezing, this is a core temperature of −15 degrees C (5 degrees F) for at least 96 hours, −20 degrees C (-4 degrees F) for at least 24 hours or −35 degrees C (-31 degrees F) for at least 15 hours. Heat treatment is at least 60 degrees C (140 degrees F) for 1 minute.

Traditional dry salting processes of anchovies inactivated Anisakis. Studies on other traditional processes such as air-drying and double salting also suggest that anisakids are inactivated.

Advanced processing techniques for cutting, which include gutting and trimming operations could have a significant impact on ensuring parasite-free products for consumers.

Scientists said further work should focus on detection and inactivation methods. They also said a survey should be undertaken at the processing stage to address data gaps on the occurrence of zoonotic parasites in fish species commonly produced in open systems.

Experts are also working to see if any wild fish species from specific fishing areas pose a risk to public health due to zoonotic parasites.