Aquaculture fish have practically no risk of infection from parasites such as anisakis.

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In Spain up to 40% of some species of fish may be contaminated by the anisakis parasite and eating raw or undercooked fish increases the risk of suffering from this allergy. However, the Marine Zoology research group of the University of Valencia, within the framework of the project Anitest, has shown that the anisakis parasite has “very limited” infection success and it is almost always degraded by antiparasitic processes that occur during the ingestion and digestion of the fish.

The publication of various articles that demonstrate the vulnerability of farmed fish to the anisakis parasite has led this research group to have experimentally evaluated the infective susceptibility of fish to exposure to this parasite. The results that emerge from the project, which has just ended, show that, in the unlikely event that the parasite reaches crops, “the fish are not very susceptible to being infected.”

As reported by the academic institution in a statement, until now it had been considered that aquaculture is a “free space” for anisakis, since the fish are fed with feed free of the parasite. However, recent articles have cited “sporadic” cases of the parasite in farmed fish. In fact, anisakis is capable of infecting practically any fish.

The research has been led by the group of Marine Zoology of the Cavanilles Institute of Biodiversity and Evolutionary Biology (ICBiBE) of the University of Valencia, Anitest, you just posted your results. In addition, it has had the collaboration of the Biodiversity Foundation of the Ministry for the Ecological Transition and the Demographic Challenge, through the Pleamar Program, co-financed by the FEMP.

The project has focused on evaluating the actual susceptibility of the crop species, in case of exposure to the parasite, as well as in developing procedures to know the infective potential of anisakis. The study highlights that the infective capacity of anisakis is relatively low, since only 10% of the parasites manage to infect the fish.

“The fact that the parasites were mobile and apparently normal in appearance did not imply that they were viable, in the same way that immobile and damaged parasites managed to infect fish“, Has detailed Alejandro López, ICBiBE researcher and one of those responsible for Anitest.

The expert explains that this low infection capacity “is further reduced by the fact that, among the limited percentage of parasites established in fish, there were numerous live, encapsulated worms that presented notable external and internal damages, which would hinder their infective capacity ”.

Six hours

The team has observed that the time required for these parasites to penetrate the fish digestive tract and establish themselves in the visceral cavity is very short – from six hours after ingestion. He has also observed that anisakis is established only on the surface of the viscera and in the connective tissue, never in the muscle of the fish, which is important since the latter is the part used by the consumer ”.

The study highlights the need to develop standardized experimental models of infection, that allow to know if anisakis is capable of infecting in different scenarios of ecological, epidemiological and sanitary interest.