Anisakiasis hazard varies depending on the origin of the fish, according to a study

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University of Granada

A research team of the University of Granada (Spain) has confirmed a higher presence of the parasite Anisakis spp in anchovies of the Atlantic South East coast and the Mediterranean North West coast, and they insist on freezing or cooking fish before consuming it. Although restaurants are required by the European Union and the Spanish law to freeze the hours at -20 ºC", say the UGR scientists, who have also detected Anisakis spp larvae and another similar parasite, the Hysterothylacium aduncum, in anchovies at the West of the Mediterranean Sea and the East of the Atlantic Ocean.

"The risk of contracting anisakiasis by ingestion of anchovies (Engraulis encrasicolus), may be influenced by the geographic area of catching, as there is a great variation in the parasites (average prevalence and intensity) of anchovies of different areas", explains to the platform SINC Adela Valero, main author and researcher of the Department of Parasitology of the UGR.

The study, which has been recently published in the International Journal of Food Microbiology, has analysed 792 anchovies caught between October 1998 and September 1999 in the fish market of Granada. Half of them came from the East of the Atlantic Ocean (Gulf of Cadiz and Strait of Gibraltar) and the other 396 of the West of the Mediterranean Sea (Alboran Sea, Mar Catalán, Gulf of Lion and Mar de Liguria).

According to the researchers, the parasite Hysterothylacium aduncum was more frequent in the anchovies of the Mediterranean Northeast, specifically the Gulf of Lion and the Ligurian Sea. In the anchovies caught in the Atlantic area of the Strait of Gibraltar (Gulf of Cadiz and the Strait), Anisakis is more frequent than in those coming from the Mediterranean area (Alboran Sea), "apparently due to the presence of cetaceans", points out Valero. "This connection is especially obvious in the anchovies coming from the Ligurian Sea, where the presence of Anisakis and cetaceans is higher than in the rest of the areas studied", says Francisco Javier Adroher, other of the authors and researcher of the UGR. This involves a higher hazard for consumers, if they do not freeze fish.

Fish muscles, habitat of the larvae

Another factor that increases the probability of infection for the parasite is the migration of the larva to the fish muscle. According to the scientists, "the higher presence of the parasite in the muscle increases the risk of contracting anisakiasis with the consumption of pickled anchovies". The scientists of Granada have also proved that the presence of the parasite in fishes increases depending on the fish size. "As pickled anchovies are prepared with bigger ones, the risk also increases", adds Adroher.

Valero and his team point out that more studies are required to identify the marine areas with a higher presence of parasites which can affect human health. This way it will be possible to determine if the abundance of the parasite in certain areas varies with time, "which would allow to design and apply measures to limit human exposure to such parasites".

Source: University of Granada