Anisakis poisoning seems to have become very common. However, the media coverage and the boom in sushi consumption may have blurred the data
In recent days, anisakis poisoning has covered the covers of various media, even talking about cases of allergy, something rarer still. It should be noted, on the other hand, that since we are in the middle of summer, food poisoning is much more common than in colder times: we cook less and eat more food raw or undercooked.
It's more. As we discussed last year, according to the OCU, fish is the second most likely food to cause food poisoning in summer (9% of the total, after eggs), being anisakis poisoning the most common among them. That is why today we will specifically review what we know about anisakis: what it is, why it has become so “popular”, where it is found and how we should treat food to avoid its poisoning.
What is anisakis
As the Spanish Agency for Consumption, Food Safety and Nutrition (AECOSAN) explains, anisakis is a parasite commonly detected in fish and cephalopods (octopuses, squid, cuttlefish and other related animals). The most common symptoms associated with anisakis tend to focus on the digestive system (anisakiasis), although it can also lead to serious allergic reactions.
The anisakis develops its life cycle in marine mammals such as whales or dolphins, but when it is in the so - called "larval stage" is fish, which are ultimately consumed by these larger animals, reaching enter the food chain of humans.
It should be noted that, as with other parasitic infections, anisakis cannot reach its adult stage in humans. It only completes its cycle in marine mammals, where it becomes an adult and releases eggs into the sea through their feces, thus being consumed by other smaller fish. In humans it is only capable of forming larvae and infecting the digestive system, which tries to eliminate it, giving rise to digestive ailments and even requiring surgery in some cases to remove the larvae, as was the case of a man who consumed sushi in Portugal last year 2017.
Among the most common symptoms associated with ankisakis is severe abdominal pain, nausea and vomiting, similar to severe gastroenteritis, in some cases being confused with appendicitis if the pain in the lower abdomen. On the other hand, anisakis is also capable of causing allergic symptoms, such as itching, skin lesions and even anaphylaxis. In fact, it is more common to suffer an allergy to anisakis than abdominal pain, but since they are not typical symptoms of food poisoning, they can be confused and not diagnosed correctly. In these cases of suspected allergy, the recommendation is not to consume any type of raw fish to avoid risks.
Where is the ankisakis found
Although in recent days there has been a tendency to directly associate raw fish with anisakis, not all fish contain this parasite.
In Spain, one of the countries with the most ankisakis infections according to a study published in Scientific Reports, homemade anchovies and pickled anchovies (this fish being responsible for 8,000 cases of anisakis per year) , and pickled fish in general they are the most likely to cause anisakis infection. For their part, hake, sardines and bonito are usually caught at great risk. Likewise, sashimi, sushi, carpaccios and other raw fish would occupy a second place according to AECOSAN. Next, marinated fish, raw roe, herring and other crustaceans and smoked fish would also be at risk.
All these fish and derivatives must be frozen if they are made at home. If they are bought already prepared, the freezing must have already been carried out correctly by the manufacturer and / or seller, by law.
Freshwater fish such as trout, perch, panga or carp are free of danger. On the other hand, aquaculture fish, such as salmon, sea bream or seabass (most of them produced in farms and fed with feed) do not usually represent a danger, although the risk is still present to a lesser degree, and must have received the same treatment and the relevant freezing by the seller of said fish.
Finally, AECOSAN affirms that it would not be necessary to freeze foods such as oysters, mussels, clams, coquinas and other mollusks. Likewise, in addition to the aforementioned freshwater fish, semi-preserved anchovies (in metal or glass containers) and dried and salted fish such as cod and mojamas would not require such treatment either.
How to prevent anisakis poisoning
In addition to avoiding consuming the aforementioned fish raw, the AECOSAN advises buying the fish previously clean and without entrails (and if they still have them, they should be eliminated as quickly as possible). Subsequently, it must be cooked using methods that reach 60ºC or more for at least one minute.
Among the most common cooking methods that usually kill the parasite, if it is found in fish, are cooking, frying, baking or grilling. Always at the indicated temperature for more than a minute throughout the piece to be consumed. However, this method is not totally foolproof.
Currently, the best prevention method to avoid anisakis poisoning is the previous freezing of the fish: it should be frozen at -20ºC for a minimum of 24 hours, and as a general recommendation for at least five days in three-star refrigerators, something unusual in conventional home refrigerators, which is why AECOSAN advises in these cases to buy the fish already frozen.
Finally, if anisakis larvae or eggs are still detected in a piece of fish and they are completely removed, theoretically such fish could be consumed. However, this practice is not recommended, especially in the case of an anisakis allergy, since even if the parasite is completely removed, there may be protein remains in the piece that could also lead to allergy.
Has anisakis become resistant?
Although it seems that anisakis infections have increased, the situation is not such, since anisakis has always behaved the same, and its infection cycle has not changed. The problem is that anisakis was previously related to Japan and sushi, since this country traditionally consumes a lot of raw fish. But Spain too, as is the case with anchovies in vinegar, but the cases went more unnoticed.
On the other hand, home-made freezing methods are often overestimated, as we have already mentioned: a temperature of -20ºC is required for several days, and most home-made refrigerators are not capable of reaching it. Just by reaching -17ºC an imperfect freezing is already produced, being able to leave some parasites alive, which will develop excessively during the thawing period of the fish.
Likewise, and although cases of anisakiasis have appeared in theoretically frozen fish, the president of the scientific committee of the Spanish Society of Community Nutrition (SENC), Javier Aranceta, affirms that it has not been shown that anisakis has become resistant to cold: it is more likely that a loose freeze has just occurred.
What has occurred this summer is a greater media coverage of the cases of anisakis, along with a greater consumption of raw fish, given that the fashion for homemade sushi and other preparations has been on the rise in recent years. In addition, fish catching practices also help in part, since they tend to take large catches and clean the viscera in situ, to immediately freeze the fish; that means throwing the viscera into the sea, which can be infected and consumed by other fish or mammals, where the anisakis can continue its cycle. In fact, some Spanish fishing boats have already suggested treating these viscera with heat before throwing them into the sea to eliminate the anisakis.
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