LivingEverything there is to know about anisakis

Everything there is to know about anisakis

In Spain, it is estimated that there are 8,000 cases of anisakiasis per year , that is, of parasites by anisákidos, according to the model of the Marine Research Institute of Vigo, belonging to the CSIC. The reasons for this are the amount of fish we eat, one of the highest in Europe (about 26 kilos per inhabitant and year) as well as our way of preparing it, which does not kill the parasite. See pickled anchovies, little cooked roasted sardines … And for a few years now, our taste for exotic fish-based preparations such as sushi, sashimi and ceviches. But can you do something to avoid being parasitized by these worms? Of course!

Anisakis is a parasite that can be found in marine fish and cephalopods (squid, octopus, cuttlefish …). Its adult larvae can be detected with the naked eye. Eating fish with anisakis usually causes digestive disorders such as gastroenteritis, stomach pain, vomiting, nausea, constipation, diarrhea … and an allergic condition that can range from hives to anaphylaxis (serious allergic reaction).

The biological cycle of Anisakis simplex is broadly as follows: fertilized eggs are expelled into the sea through the faeces of definitive hosts (large marine mammals). These eggs house the larva in its initial state (L1) from where it will evolve to the L3 state. To get to L3, the larva needs to parasitize other fish, stay in them, and it does so by first passing through the crustaceans of the plankton. Fish, cephalopods, and whales will eat the plankton and be parasitized . They will also become parasitized if they ingest fish that are already contaminated with anisakis larvae. The parasite will have already reached level 3 and this is when humans come into action, we will be parasitized if we eat raw or undercooked contaminated fish dishes .

Once the person has ingested the anisakis larvae, they enter the body through the mucosa of the digestive tract. Three clinical forms are distinguished: gastric, intestinal, ectopic.

Gastric form . It occurs when the larva enters the digestive tract. The symptoms of its presence will appear in less than twelve hours and consist of severe pain in the upper abdomen, nausea and vomiting .

Intestinal form . In this case, symptoms will appear between 48 and 72 hours after eating contaminated fish. Acute abdominal pain, vomiting, nausea and alteration of the intestinal rhythm usually occur causing constipation or diarrhea. The symptoms can be similar to acute appendicitis .

Extragastrointestinal or ectopic . It occurs on rare occasions and what happens is that the larvae perforate the gastric or intestinal wall, reach the abdominal cavity and migrate to different areas: peritoneum, lung, pancreas, liver … “When this happens, in the most serious cases it can surgery will be necessary . On even less frequent occasions, the larvae are capable of going up from the stomach to the oropharynx, causing the expulsion of the larva with coughing ”, tells us María Teresa Audicana, allergist at the IMQ Amárica Medical Center in Vitoria-Gasteiz, an expert in allergies food and children and member of TopDoctors.

According to Audicana, what most often occurs after ingesting anisakis is an allergic condition within half an hour or two hours after eating the infested fish . The symptoms are: urticaria on the skin (hives), swelling of the lips or eyelids, abdominal pain, feeling of fullness or fullness, nausea, vomiting and / or diarrhea, palmoplantar and genital itching and in more severe cases dizziness, loss of consciousness and feeling of death.

No. Anisakidosis refers to the parasitization in humans of the genus Anisakis , Pseudoterranova or Contracaecum . If we talk about anisakiosis we will be referring to parasitization by the genus Anisakis although the term anisakidosis is also used for the same. Anisakis allergy is allergy to the parasite (to its protein).

The good news is that humans are not the best hosts for anisakis and the L3 larva does not usually thrive to the adult stage within our body. The parasite is either eliminated through feces or vomiting, or it dies in about 15 days.

“The most effective treatment for gastric anisakiosis is the extraction of the larvae during endoscopy , which entails diagnostic confirmation and the consequent disappearance of the symptoms in a few hours. In intestinal anisakiosis, on many occasions, surgical intervention and resection of the affected fragment is necessary. However, when the suspicion of intestinal anisakiosis is strong, conservative treatment with fluid therapy and antibiotics may be sufficient for cure. In colon anisakiosis , the larvae can be successfully removed by colonoscopy. Although numerous antiparasitic treatments (anthelmintics) have been investigated such as pyrantel pamoate, thiabendazole and ivermectin among others, there is currently no effective pharmacological treatment. The larvae of A. simplex (genus of anisakis responsible for human parasitization) have been highly resistant to this type of drug, while those of P. decipiens (genus of anisakis that also parasitize humans but to a lesser extent, known as cod worm) appear to be sensitive to ivermectin, at least in in vitro studies, ”says allergist María Teresa Audicana.

Any marine fish can be infected with anisakid larvae . If we look at the species that we usually consume the most, the most affected are: herring, sardines, anchovies, pollock, hake, salmon, tuna, turbot or monkfish , among others. Hake, being one of the most consumed fish in Spain, is highly parasitized. Anisakis larvae can also parasitize cephalopods such as octopuses and squid .

Audicana states that the fish that are free of anisakis are bivalves (oysters, clams, cockles, mussels …) , crustaceans (shellfish) and river fish (trout, carp, perch) .

Anisakis is a pearly white worm about two centimeters long that can be found in the viscera of parasitized fish. It can also be seen in a spiral shape on the skirt of the fish.

To avoid contracting anisakiasis, what you have to do is not eat raw parasitized fish or that has been cooked so that the parasite has not been killed . These are the recommendations that AECOSAN (Spanish Agency for Consumption, Food Safety and Nutrition) give to avoid parasitization:

Buy the fish clean and without entrails (guts). In case it has not been cleaned in the fish shop, it should be done at home as soon as possible, removing the viscera and washing the surrounding area well to prevent the larvae from passing from the viscera to the fish meat and

Cook, fry, bake or grill at 60ºC for at least one minute and the whole piece. In the blog Gominolas de Petróleo by Miguel A. Lurueña, graduated in Food Science and Technology from the University of León and Agricultural Technical Engineer (Specialty Agricultural and Food Industries) from the University of Salamanca, its author writes that this is easy to do. get when we cook, bake or fry but it can be more difficult if we prepare the fish on the grill or in the microwave , so we will have to pay attention.

-Although the allergist consulted affirms that crustaceans do not have anisakis, AECOSAN recommends following the previous recommendation with lobster, prawn, lobster, prawn, shrimp, crab, spider crab …

– If the fish is to be consumed raw or in preparations that do not kill the parasite, it must be frozen beforehand. If we are going to freeze at home, we have to make sure that the refrigerator reaches a minimum of -20ºC (refrigerators with three stars or more) and keep the fish frozen for five days. In case our refrigerator is not three stars, it is recommended to buy the fish already frozen.

Following the AECOSAN recommendations, we will have to freeze these preparations if we make them at home . If we buy them prepared it will not be necessary because the freezing will have been done by the manufacturer.

Anchovies in vinegar and pickled fish.

Sashimi, sushi, carpaccios and other specialties based on raw fish.

– Marinated fish, such as ceviche or salmon .

– Raw or practically raw fish roe.

Herring and other raw fish prepared in brine or slightly salted.

– Marine fish subjected to cold smoking.

Oysters, mussels, clams, coquinas and other bivalve mollusks.

– Fish from inland waters (rivers, lakes, swamps …) and freshwater fish farms . For example: trout, carp … If the fish comes from a saltwater farm, Miguel A. Lurueña points out that there is a minimal incidence of anisakis “but in any case, the prevalence depends on the practices that are carried out, so don’t let your guard down ”.

Semi-preserved foods such as anchovies (in metal, glass or other presentations).

Dried fish salted in a traditional way , such as cod or mojamas that we buy already prepared.

As stated on the AECOSAN website, European and Spanish legislation oblige businesses not to sell fish with visible parasites .

“In addition, establishments that serve food to final consumers or communities or that produce these products for sale to the final consumer, must guarantee that the fishery products to be consumed raw or after preparation that is insufficient to destroy parasites have been previously frozen under the conditions established by law . National legislation also obliges these establishments to inform consumers that fishery products to consume raw or after preparation that is insufficient to kill parasites, have been frozen. If they do not have this information, the consumer can request it ”, it can be read.

“The presence of anisákidos in the last ten years in fishery products is increasing, due to marine pollution and fishing practices. It could be stopped, improving gutting practices in fishing vessels (that the viscera are not thrown into the sea because if they are contaminated they will return to the food chain of the fish), improving the labeling of fishery products indicating the recommendations to follow (heating 60ºC, freezing -20ºC for more than 24 hours) and developing a vaccine against allergy to anisakids ”, says Mónica Carrera, biologist and researcher at the Marine Research Institute IIM-CSIC in Vigo.

At the Marine Research Institute IIM-CSIC in Vigo, Mónica Carrera and her team are working on a vaccine that would be aimed at patients allergic to the different anisakid species belonging to the Anisakis , Pseudoterranova and Contracaecum genera. It is in the experimental phase and, at the moment, studies have been done only in mice.

The IIM-CSIC Marine Research Institute of Vigo has also developed the fastest method available to date to detect anisakids in any food product . “For this, a biomarker protein is monitored by means of a mass spectrometry equipment. Thus, in just two hours we can detect the presence or not of anisakids in any food (fresh, frozen, processed, pre-cooked). This method has been awarded by the Royal Galician Academy of Sciences . This method could be implemented in laboratories of food control authorities and / or laboratories of the food industry ”, Carrera tells us.

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