Anisakids In Fish, Squid: Symptoms, Life Cycle, Are They Dangerous To Humans?

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Anisakids In Fish, Squid: Symptoms, Life Cycle, Are They Dangerous To Humans?
Anisakids In Fish, Squid: Symptoms, Life Cycle, Are They Dangerous To Humans?

Video: Anisakids In Fish, Squid: Symptoms, Life Cycle, Are They Dangerous To Humans?

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Video: Anisakiasis | Anisakis | Life cycle, symptoms, treatment | By phanindra gupta 2023, February

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  • What are Anisakida
  • Habitat and ways of infection
  • The structure and life cycle of anisakida
  • Symptoms of anisacidosis
  • You can defeat parasites!

Pinworms, roundworms, bovine and pork tapeworms, flukes - all these and other "popular" helminths are well known.

It would seem, what other new parasites can appear and pose a threat to us? However, this is exactly what happened when a man died in 1955 in the Netherlands after eating too much lightly salted herring contaminated with anisakids.

What to do in such a situation? To get started, we recommend reading this article. This article details the methods of dealing with parasites. We also recommend contacting a specialist. Read the article >>>

The fatal diagnosis was anisacidosis. Let's see what it is, what the anisakids themselves are and how they are dangerous to humans.

Anisakids in fish
Anisakids in fish

What are Anisakida

In fact, anisakids have long been known to science, it was just that earlier it was believed that they are harmless to humans, since after entering their body, their larvae do not go through the subsequent stages of development to sexually mature.

However, the larvae, as it turned out, are enough to cause irreparable harm to our body. Of course, irreparable only if you do not diagnose this helminthiasis in time and do not take up treatment.

Despite the primitive structure, anisakids, or rather, their larvae, localized in the human intestine, are able to perforate its walls, practically piercing them and thereby causing edema and inflammation.

In severe cases, anisacidosis can result in intestinal obstruction up to peritonitis, which is a fatal threat.

What are Anisakida
What are Anisakida

Habitat and ways of infection

Until recently, anisakida and the anisakidosis caused by them were recorded mainly in countries and areas on the sea or ocean coast, where a lot of fish is usually consumed. No wonder the second name of this worm is herring worm.

It should be noted right away that anisakida is not transmitted from person to person. It is fish and seafood that have not undergone appropriate heat treatment that are the main source of infection.

Therefore, it is quite natural that earlier in our country anisakids were recorded mainly in the Far East and Kamchatka.

There are many cases of anisacidosis in Europe (Scandinavia, Great Britain, France), in North and South America, and especially in Japan and Southeast Asia, where seafood traditionally constitutes a significant part of the diet.

The data of scientific research do not inspire optimism: according to their results, in herring and in such red fish as chum salmon caught in the Sea of ​​Okhotsk, the infection with anisakids is 100%.

In the Pacific Ocean, the situation is somewhat better: for example, in hake the infection rate is 50%, in pollock - 35%, in pink salmon, pollock, cod, mackerel, and in squid the level of infection is also quite high.

That is why it is strongly recommended to exclude raw, semi-raw and slightly salted fish from your diet - this is the most reliable prevention of anisacidosis.

The structure and life cycle of anisakida

Anisakids do not look threatening at all - they are small round worms (nematodes) with a cylindrical body shape, 1-2 mm in diameter and up to 5 cm long.At one end there is a mouth opening with three lips, on the other - an anal opening, and between them - a gastrointestinal tract.

The life cycle of these parasites occurs with repeated changes of hosts, so its description is of particular interest.


Each parasite has its own hosts, and anisakids are no exception. Their main hosts are marine mammals (whales, seals, dolphins, fur seals, walruses), and intermediate at different stages:

  • on the first - crustaceans;
  • on the second - marine and anadromous ichthyofauna (herring, cod, salmon, sardine, etc.), as well as cuttlefish and squid.

As for man, he is classified as a random host, like those animals and birds that eat raw fish.

So what does the life cycle of anisakida look like?

  • Adults parasitize marine mammals, from where their eggs, along with the host's feces, enter the water.
  • In the water, larvae appear from the eggs.
  • The larvae are consumed by crustaceans (this is the first intermediate stage).
  • Crustaceans are consumed by fish and squid, in which the larvae of anisakida grow up to 3 cm (second intermediate stage).
  • Fish and squid are consumed by marine mammals, in whose bodies the larvae turn into mature individuals of anisakids, produce eggs, and the process continues in a circle.
The structure and life cycle of anisakida
The structure and life cycle of anisakida

Anisakidosis occurs when larvae enter the human body with contaminated seafood, therefore, the question at what temperature anisakidi die is extremely relevant.

Unfortunately, nature has taken good care of these parasites: their larvae feel great in a wide temperature range, up to + 45-50 ° C, and only after a 10-minute heat treatment at + 60 ° C do they still die.

To kill them with cold, you will need to keep the fish for at least two weeks at a temperature of -18 ° C, but at -30 ° C it will take again 10 minutes.

So salting, smoking or freezing infected fish is useless - this is unlikely to save you from getting anisacidosis.

Sometimes you can hear the question: is it possible to eat fish with anisakida? In principle, if it has undergone a high or low temperature heat treatment as described above, the answer can be yes.

However, it is enough to examine such a fish not even under a microscope, but with the naked eye, as any appetite will disappear: not only can adult anisakids be found in it, usually when the fish dies, the larvae from the abdominal cavity move into the meat, and this is very good in the photo it is seen.

Symptoms of anisacidosis

Like other helminths, the vital activity of anisakids is accompanied by the release of a significant amount of toxic substances, which, in addition to specific symptoms, also cause general intoxication of the body and the development of allergies.

Clinical symptoms when infected with anisakids may not appear for a couple of weeks, and then they are determined by the localization of the larvae, which have time to gain a foothold in the stomach or intestines.

Take an anisakid test

Symptoms Answer Muscle weakness Yes Not Cough Yes Not Stomach ache Yes Not Headaches Yes Not Vomiting Yes Not Weight loss Yes Not Skin rashes Yes Not Flatulence and rumbling in the stomach Yes Not Diarrhea Yes Not Heat Yes Not

With the gastric form of anisacidosis (the most common), the following symptoms appear:

  • abdominal pain of an incomprehensible nature in the epigastric region;
  • nausea and vomiting, often with blood streaks or few clots - this is considered the most reliable indication of the presence of anisakids;
  • toxic-allergic edema and skin rashes resembling urticaria, in various places - a combination of these phenomena also indicates anisakidosis;
  • febrile condition with high temperature (sometimes above 38º);
  • in the case of retrograde, that is, the opposite, the ingress of larvae from the stomach into the pharynx and the esophagus, a cough appears, the throat is tickled.

With the intestinal form of anisacidosis, the following symptoms appear:

  • intense acute pain in the abdomen, localized in the navel;
  • flatulence and rumbling in the stomach;
  • diarrhea with mucus and small streaks or blood clots.

Anisakidosis can occur in acute, subacute and chronic forms. If such symptoms take an acute form, then there is a risk of serious complications (intestinal obstruction, inflammation of the peritoneum, peritonitis).

What to do if two or three symptoms appear at the same time? If you do not consult a doctor on time, then the prognosis is extremely unfavorable, even fatal.

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