Spain is the European country with the highest number of cases of infection by the parasite
Source of heart-healthy omega-3 fatty acids, proteins of high biological value, minerals such as calcium, iodine and selenium, and vitamins B and A. fish provides unquestionable nutritional benefits, but it also has a dark side: contamination by mercury or persistent chemical substances (POPs) - pollutants that remain in the environment and in the food chain -, bacterial infection and infestation by parasites, which pose a threat to human health.
As far as parasites are concerned, the famous anisakis, which causes a chronic allergy in those who have the misfortune to ingest alive one of these worms that coil up in the flesh of fish, is the great threat in developed countries. And despite the fact that for 12 years now restaurants in Spain have been obliged to freeze fish to kill any survivors of the species, the alert is growing as it infests more and more fish.
The most dangerous dish: anchovies in vinegar
In fact, according to a study published in NatureSpain is the country with the highest incidence in Europe and the culprits are in large part anchovies in vinegar. So you know, if you want to reduce your chances of becoming infected, avoid them. "More and more medical cases of anisakiasis are being reported," the report says, "although the exact extent cannot be known due to the scarcity of epidemiological data."
The advance of this parasite could be slowed downJavier Borderías, of the Institute of Food Science and Technology (ICTAN), of the CSIC, believes that "prohibiting fishermen from throwing overboard the remains of fish gutted at sea".
And anisakis is not alone: "The biodiversity of parasites in wild fish is very large," explains Santiago Pascual, from the Institute of Marine Research of the Spanish National Research Center (IIM-CSIC) and one of the authors of the research of Nature. "We talk about hundreds of species, but only a dozen make up a dirty list. that must be properly managed because of their potential impact on the quality and safety of fish".
More allergies to fish, but less to other allergens?
That dirty list includes, in addition to anisakis and its congeners, many other parasites that can be found in different types of fish: cryptosporidium and giardia in bivalve mollusks (mussels, clams, razor clams, etc.); trematodiasis in pelagic fish (anchovies, sardines, bonito...); kudoa in gadids (cod); microsporids in demersal fish (hake, sea bream, monkfish...) and mesoparasites and muscular cestodes in large teleosts (tuna).
One consequence of this omnipresence of parasites is the increase in the number of people allergic to them, although Africa Gonzalez, president of the Spanish Society of Immunology and director of the Biomedical Research Center (CINBIO), clarifies that not all parasites cause the same allergic reaction or the same symptoms. Some cause severe reactions, such as asthma or anaphylactic shock, or serious health problems, including liver cancer, as in liver fluke infestations, which are common in Southeast Asia and South America.
But there are also those that can protect against allergies, as in the case of infections by certain types of helminths (worm-like parasites): it is thought, says the immunologist, that "... they can also protect against allergies, as in the case of infections by certain types of helminths (worm-like parasites).more developed societies with less infection by helminth-type parasites have more allergies to different allergens".
The Spanish anisakis vaccine
The worst thing is that, once the allergy to fish or its parasites has developed, it remains forever, with the aggravating factor that "those allergic to anisakis, even if they freeze or cook the fish well and the parasite is dead, may have reactions.caused by traces of parasite proteins," says Gonzalez. Diagnostic tests, such as those developed at the IIM-CSIC, are of great help in these cases. "They consist of proteomic techniques -large-scale study of proteins- for the detection, in less than two hours, of parvalbumins or anisakids in any food product," says researcher Mónica Carrera, from the IIM-CSIC.
However, the best solution for those allergic to fish and anisakids would be to have a vaccine, a project on which CINBIO and IIM-CSIC are working and which already has several firm candidates to become the cornerstone of a possible vaccine.
And if you are thinking of switching to farmed fish to get around the dirty list of parasites, Santiago Pascual puts the record straight: "The fish is a very good fish," he says.In aquaculture fish, the list is more or less as extensive as in aquaculture fish.However, the parasites that affect the productivity of aquaculture exploitation have a greater weight than in extractive fishing".
In the end, as a consumer, he believes that "just as we all perceive that the quality of a product is highly variable depending on the species and the operator who markets it, the food safety of the fish on our plate is a direct consequence of how risks have been managed in the chain of command, and it is evident that not all products, operators and markets are equally demanding".
Fish, maximum two days in the refrigerator
If you do not want to give up sushi and anchovies in vinegar, freeze it at -20ºC for at least 48 hours. Careful: not all domestic freezers reach such low temperatures, in which case it is necessary to extend the time up to one week.approximately. In addition, these recommendations will allow you to reduce the risk of parasitic infestations and bacterial infections:
- Buy fish from reliable suppliers and establishments.
- Discard fish that smell too fishy or acidic (not fresh).
- Check it for parasites (sometimes they are visible).
- When you come home from shopping, do not leave fish out of the refrigerator for more than two hours because bacteria multiply rapidly at room temperature.
- If you do not freeze fresh fish, store it in the refrigerator and consume it within two days at the most.
- Wash hands after handling raw fish to avoid contaminating other foods.
- Marinating, vinegar or smoking reduce parasites, but do not eliminate them completely, so fish to be prepared with these techniques should be frozen.
CAN THEY PARASITIZE HUMAN BEINGS?
Yolanda González-Amores, specialist in Digestive System at Hospital Punta de Europa, in Algeciras, found an exceptional case: "Three live larvae of Hysrterothylacium aduncum [an anisakis-type worm] anchored in the gastric mucosa."
The doctor emphasizes that this is a unique case in every aspect, which is why it was published in the Spanish Journal of Digestive DiseasesThe man was infected by a rare parasite after eating pickled anchovies bought in Malaga. He came to the hospital with very strong abdominal symptoms and after ruling out intestinal perforation, an endoscopy revealed the three live larvae (causing intense inflammation). When the parasites were removed from the mucosa, the symptoms disappeared and no treatment was necessary".
This case supports the recommendation to "never eat raw or undercooked fish", stresses the digestologist and insists that "the typical sushi is behind the increase in allergies and intolerances associated with the consumption pattern of this type of food".
"The general recommendation is to subject it to some thermal process, from cooking at temperatures above 60 degrees Celsius until frozen at -20ºC for at least 48 hours. These guidelines prevent the anisakis larvae from penetrating the intestinal wall of people and avoid sensitization leading to allergy," explains Javier Borderías, from the Institute of Food Science and Technology (ICTAN), of the CSIC.
