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Culinary specialties raw such as swordfish, tuna, sea bass or salmon carpaccio, sushi and sashimi they are among the most popular foods in the summer. If in the past the use of raw fish in our country was limited to the preparation of typical dishes such as marinated anchovies and bottarga, which is not free from risks, with the advent of multiethnic cultures and traditions, the consumption of raw or undercooked animal products has further increased.
But experts warn: the possibility is high that the raw fish is infested with Anisakis, a dangerous pathogen for both acute and chronic forms of poisoning, extremely widespread also in the Mediterranean, where there are species of fish, such as the mackerel and scabbard fish, which reach 70-100% infestation in the catch.
Symptoms of anisakidosis
Once ingested, anisakid larvae often they die and do not cause disturbances. In some cases, however, they can invade the mucosa of the stomach or intestines causing the gastrointestinal anisakidosis.
There acute form of the infection is generally the gastric one, characterized by symptoms such as nausea, vomiting and pains in the “pit of the stomach” that may appear 4 to 6 hours after eating infested fish. In the intestinal form, however, the signals can occur even 7 days after infection with fever, increased white blood cells (leukocytosis), vomiting, diarrhea, abdominal pain and nausea. Sometimes, the larvae can puncture the gastrointestinal mucosa, causing bleeding.
In rare cases, the larvae are located outside the gastrointestinal tract (in mesentery, a folding of the membrane that lines the abdominal cavity, into the abdominal cavity etc.).
They can also provoke allergic manifestations of varying degrees ranging from urticaria conjunctivitis up to, in severe cases, anaphylactic shock.
Incubation, diagnosis and therapy
In humans, which is an accidental host, these parasites cannot develop until adult stage. In fact, in the human body the anisakids generally remain for no more than two weeks, ending up engulfed in a small aggregate of inflammatory cells called a granuloma.
Once the diagnosis through endoscopic examination, in general – the ISS experts write – the best cure is the endoscopic removal of parasites from the gastrointestinal tract, whenever possible (in gastric forms). However, in severe cases, for example in intestinal obstruction, appendicitis or peritonitis, a surgery. Cases have been described in which treatment with antiparasitic drugs which albendazole has led to therapeutic success.
How to prevent Anisakis intoxication
The freezing and the cooking fish and shellfish are the two most effective methods of avoiding an anisakid infection.
With the decree of 17 July 2013, the Ministry of Health has made it compulsory to display in the points of sale of a sign in a clearly visible position bearing the following information: “Consumer information for a correct use of fish and fresh cephalopods. In case of raw, marinated, not fully cooked consumption, the product must be preventively frozen for at least 96 hours at -18 ° C in a domestic freezer marked with three or more stars “.
To prevent anisakidosis it is therefore recommended to:
- Remove the bowels from the fish as soon as possible in order to decrease the risk of the passage of the larvae from the visceral cavity to the muscles (parts that are eaten).
- Make sure that the fish in its entirety, even the largest parts, is frozen at minus 18 degrees (-18 °) for at least 96 hours (only industrial freezers or household freezers with three or more stars can reach this temperature). Only after this treatment can raw fish (sushi, sashimi, carpaccio, cold smoked fish, marinated fish) or undercooked fish be consumed
- Cook the fish, taking into account that, to be sure of killing the larvae, the inside of the fish, even the largest parts, must reach a temperature above 60 ° C for at least 10 minutes.
At the level of retail outlets or restaurants the use of the so-called blast chiller, an instrument capable of inducing a very rapid drop in temperature below -20 ° C for at least 24 hours. Restaurants and fishmongers must also indicate to the consumer which of their products have been slaughtered.
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