Anisakiosis is a parasitic disease caused by the nematodes of the genera Anisakis, Contracoecum and Pseudoterranova. The infection occurs through the consumption of fish infected with nematodes. What are the symptoms of anisakiosis? How is the treatment going? Is it possible to avoid this parasitic disease?

Anisakiasis(Latinanisakiasis , anisakiasis) is a parasitic disease that is most widespread in areas where raw fish are eaten, in light brine or s alted, smoked fish are also dangerous if the temperature of heat treatment does not reach 60 ° C, among others. in Scandinavia, Japan, South America, the Netherlands.

These parasites are rare in seas with low salinity such as the B altic.

The increase in the percentage of fish infected with nematodes is followed by the common practice of gutting fish caught while still on board and throwing their insides overboard, which spreads the disease to other fish.

Anisakiosis: the life cycle of nematodes

Nematode eggs (Anisakis) are released into the seawater, where they undergo different larval stages. Immediately after hatching, they are ingested by the first intermediate hosts, usually small crustaceans that form krill.

Krill, in turn, is eaten by fish and reaches the larval stage in their bodies. The fish are then eaten by the ultimate host of marine mammals - dolphins, seals, whales.

Man is their accidental host. We get infected by accident by eating, for example, herring, sushi.

The larvae are about 2 cm in size and first enter the gastric mucosa. From there, after a week, they begin to move to the small intestine. These parasites have the ability to penetrate the mucosa of the human digestive system

Anisakiosis: symptoms of infection

Symptoms may appear within hours of eating infected fish, including:

  • severe abdominal pain
  • nausea
  • vomiting imitating peritonitis

A cough later appears, in which the larvae escape through the mouth, but this is not noticeable by most patients.

As soon as the parasite enters the small intestine, there are inflammatory infiltrates of the intestine reminiscent of Crohn's disease:

  • stomach ache
  • chronic diarrhea
  • nausea
  • changes in anus
  • fever within 1-2 weeks of infection

The location of the larvae on the stomach or intestinal wall may cause a severe allergic reaction.

Larvae rarely reach adulthood inside the human digestive tract. Most often they die within a few weeks. However, even when dead before they are excreted, they can stimulate an inflammatory or allergic response that will look like:

  • hives
  • angioedema
  • asthma attack
  • contact dermatitis
  • anaphylactic shock

Anisakiosis: diagnosis

The diagnosis can be made by performing gastroscopy and extracting the larvae for parasitological examination or by taking a section of the intestinal wall for histopathological examination (image of the larvae surrounded by granulation tissue). Parasites can be visualized in a barite-contrast X-ray.

Anisakiosis: treatment

Larvae can be removed endoscopically. Obstruction of the small intestine, which may occur in the course of parasite infestation, is an indication for surgery.

Good results in the treatment of the obstruction have also been achieved with the use of an anti-parasitic drug (albendazole), which will remove the nematode from the human body.

Anisakiosis: prevention

The method of getting rid of the parasite is to raise the temperature above 60 ° C, freeze it sharply or freeze below -20 ° C for 3 days. Thoroughly clean the fish before processing.

The US Food and Drug Administration recommends that all fish and seafood intended to be eaten raw be previously frozen for 7 days in an ordinary freezer or 15 hours at -35ºC.

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