What are the dangers of eating undercooked fish?

The risk of eating raw fish

Eating raw fish in the form of sushi or sashimi, herring or other raw smoked fish, like anchovies or anchovies in vinegar or salting and Ceviche (fish lightly cooked with lemon or vinegar), carries a significant risk of infestation by Anisakis

These transparent colored worms are often confused with the muscles of the fish and hours after consumption may appear symptoms: acute abdominal pain, nausea, vomiting, and in sensitive people may occur an anaphylactic reaction -allergic- which is often confused with an allergy to seafood. If the larvae lodge in the intestine they can produce an obstruction that sometimes requires surgical intervention (this can happen up to 1 or 2 weeks after the infection).

What fish can contain anisakis?

Parasitized species are diverse, but among the most common are: cod, sardine, anchovy, herring, salmon, haddock, hake, whiting, mackerel, bonito, jack mackerel, etc., and squid, within cephalopods.

The amount of parasites varies depending on the place of capture and the moment of evisceration. In this way, fish caught in the high seas that are rapidly eviscerated have fewer parasites than those caught on the coast.

What diseases can cause us?

Once the larvae of the parasite have been ingested, they can cause two different types of pathologies: anisakiasis or anisakidosis and anisakis allergy.

Anisakiasis or anisakidosis:

In this case the disease is acquired by the consumption of live anisakis larvae due to the intake of raw, smoked, salted, vinegar, marinated or undercooked fish, in the microwave or on the grill.

The clinical picture may be mild or more or less serious. The larvae mainly affect the gastrointestinal tract and survive the different digestive secretions. They can become entangled and produce inflammation or in the most severe cases, reach perforate stomach and intestine or migrate to other tissues and organs.

The gastric form presents with abdominal pain, accompanied or not by nausea, vomiting and diarrhea, which may resemble the manifestations of other diseases such as appendicitis, ileitis (inflammation of the portion of the small intestine called the ileum), gastric ulcer, intestinal obstruction and even abdominal tumors.

There have also been 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 report having taken fish in the 48-72 hours before. The endoscopic techniques (gastroendoscopy or colonoscopy) allow to see the larvae and in turn to extract them, although in cases of greater severity, surgery may be necessary.
Allergy to anisakis:

People who have an allergy to this parasite show various symptoms after the ingestion of infested fish. These symptoms range from a simple urticaria (rash) to angioedema, which is characterized by the appearance of large welts on the surface of the skin, especially around the eyes, lips, and can also affect the hands, feet and throat. The most serious cases are associated with "anaphylactic shock" that requires hospital admission, and may be accompanied or not by the gastrointestinal symptoms mentioned above.

The diagnosis is based on the detection of antibodies (immunoglobulin E), as well as on specific skin sensitivity tests.

Anisakis information

The 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, the parasite eggs are released into the sea, which are ingested by small crustaceans that in turn serve as food for other fish and cephalopods such as cuttlefish or squid, in which the larvae mature.

The anisakis is habitually lodged in the digestive tract of the live fish and, once these die, the larvae migrate towards the viscera and the musculature, even going as far as to penetrate the skin of the fish.

The Anisakis was diagnosed for the first time in the year 1955, in Holland. But the country with the most cases of contamination is Japan, with more than 90% of the cases, due to the high intake of raw fish.
How to prevent us?

It is essential to avoid the intake of raw or undercooked fish, including homemade preparations in vinegar, smoked, salted, marinated, grilled fish or microwave insufficiently made, etc.

There are several processes to inactivate the larvae in the fish that we are going to consume, thus avoiding the ingestion of live larvae. One of the ways to eliminate them is to FREEZE raw fish at a temperature of -20 ° C or less, for at least 24 hours before consuming it.

Frozen or deep-frozen fish in the high seas, which has been eviscerated rapidly, have little chance of being parasitized.

The other variant is to eliminate it by heat, COOKING the fish at a temperature between 60-70 ° C for at least 10 minutes.

It is considered safe to consume cooked smoked fish, as well as pasteurized products.

Avoid eating raw fish, dishes made with fish not cooked in vinegar or salt, "without prior thermal due process"