Eating raw fish as sushi or sashimi, smoked herring or other fish raw, as are the anchovies in vinegar or salted fish and ceviche (fish cooked lightly with lemon or vinegar), carries a significant risk of infestation Anisakis.
These transparent colored worms are often confused with the musculature of the fish and can consume hours after onset of symptoms: abdominal pain, nausea, vomiting, and can occur in sensitive individuals-allergic anaphylactic reaction, which is often confused with an allergy to shellfish. If the larvae lodge in the intestine can cause a blockage that sometimes requires surgery (this may occur up to 1 or 2 weeks after infection).
What fish may contain Anisakis?
Parasitized species are diverse, but among the most common are: cod, sardines, anchovies, herring, salmon, pollock, hake, whiting, mackerel, bonito, mackerel, etc., And squid, in cephalopods.
The amount of parasites varies depending on the place of harvest and the time of evisceration. Thus, the fish caught at sea are quickly drawn to have fewer parasites than those captured on the coast.
What diseases can cause?
Once you have ingested the larvae of the parasite, they can produce two different types of pathologies: anisakidosis anisakiasis and Anisakis and allergy.
Anisakiasis or anisakidosis:
In this case the disease is acquired by consumption of larvae of Anisakis due to ingestion of raw fish, smoked, salted, pickled, marinated or lightly cooked in the microwave or grilled.
The clinical picture may be mild or more or less severe. The larvae mainly affect the gastrointestinal tract and survive the various digestive secretions. Are lockable and produce inflammation or in severe cases even perforate the stomach and intestine or migrate to other tissues and organs.
The gastric form presents with abdominal pain, with or without nausea, vomiting and diarrhea, which may resemble the manifestations of other diseases like appendicitis, ileitis (inflammation of the small intestine called the ileum), gastric ulcer, intestinal obstruction and even abdominal tumors.
Also found cases of joint involvement and other organs (lung, liver, pancreas and spleen).
A good medical history is essential in the diagnosis of the disease, since the vast majority of patients reported taking fish in the 48 -72 hours earlier. The endoscopic techniques (gastroendoscopia or colonoscopy) can see the larvae and in turn extract, although in more severe cases may require surgery.
Allergy to Anisakis:
People who have allergy to this parasite show various symptoms after ingestion of infected fish. These symptoms vary from simple urticaria (rash) to angioedema, characterized by the appearance of large blotches on the surface of the skin, especially around the eyes, lips, and can also affect the hands, feet and throat. The most severe are associated with “anaphylactic shock” that requires hospitalization and can go with or without gastrointestinal symptoms mentioned above.
The diagnosis is based on the detection of antibodies (immunoglobulin E), as well as specific evidence of skin sensitivity.
Anisakis simplex is a nematode (worm), a parasite that infects marine mammals (whales, dolphins, seals, etc..) And large fish. Through the feces of these animals are released into the sea parasite eggs that are eaten by small crustaceans that in turn serve other food fish and cephalopods such as cuttlefish or squid, in which the larvae mature.
The Anisakis usually stays in the digestive tract of live fish, and once they die, the larvae migrate to the viscera and muscles, even to penetrate the skin of the fish.
Anisakis was first diagnosed in 1955 in the Netherlands. But the country with more cases of contamination is Japan, with over 90% of cases, due to the high intake of fish oil.
In Spain, the first cases were diagnosed in 1991. This country now has a law prohibiting restaurants preparing dishes with raw fish, without due process prior freezing.
How to prevent it
Is essential to avoid eating raw or undercooked fish, including preparations homemade pickled, smoked, salted, marinated, grilled fish or poorly made microwave, etc..
There are several processes to inactivate the larvae in the fish we eat, thus avoiding the ingestion of live larvae. One way to eliminate them is to freeze raw fish at a temperature of -20 º C or less for at least 24 hours before use.
The frozen fish or frozen at sea, which has been gutted quickly, has little chance of be parasitized.
The other variant is removed by heat, cook the fish to a temperature between 60-70 ° C for at least 10 minutes.
It is considered safe to eat cooked smoked fish, as well as pasteurized products.
Avoid eating raw fish dishes made with undercooked fish in vinegar or salt, “without due process prior thermal”