Anisakis food poisoning is increasingly common in our country. Mainly because of the “fashion” of eating sushi and raw fish in general. And it is that sometimes we feel like expert cooks and we go around preparing a delicious salmon tataki from total ignorance of food handling. In our article today we tell you everything you need to know about Anisakis, how to prevent them and how to treat poisoning by these parasites.
Anisakis food poisoning
The first case of food poisoning by Anisakis appeared in Spain in 1995. Today, we are the first country in Europe to present cases of poisoning by these parasites. The culprits are the anchovies or rather, our way of preparing them. On the continent we are accompanied by the Netherlands (for eating infected herring) and the Scandinavian area (for cod liver). In America, the main culprit for these infections is ceviche. Worldwide, Spain ranks second in these cases; the first is occupied by Japan, due to the intake of sushi and sashimi.
Do you also like Japanese food? We love! But you must be very careful. It is quite difficult to prepare it at home following the recommendations so as not to get infected with Anisakis, basically because we do not have the proper storage conditions and we do not have food handling courses. That is why we recommend you attend restaurants that you trust and that comply with the necessary protocols.
Anisakis are nematode parasites commonly known as worms that grow in fish and marine mammals, causing lesions in their digestive tract. Ingestion of these worms by humans produces anisakiasis (parasitosis); infected fish can produce an anaphylactic reaction that can lead to life-threatening shocks.
You can easily identify these parasites. As soon as you open the fish you find them with the naked eye. They are worm-shaped, 2.5 centimeters long, white and thin and resemble threads.
According to the OCU, up to 36% of the fish we consume in Spain comes with Anisakis. Nor should you be alarmed and think that you can never eat fish again. These worms are easily removed by frying, grilling, or freezing fish; however, they survive and are ingested if you eat sushi, the so fashionable poké bowl, ceviche, and so on.
How do parasites get into the human body?
As we already anticipated, the Anisakis reach the human body through the ingestion of contaminated fish. In fresh fish, the worms are alive and move, but when they die, the parasites nest in the muscles, forming cysts. By consuming raw or undercooked fish, we increase the risk of being poisoned by these worms. A useful fact: the fish that come from the Cantabrian usually bring more Anisakis than those from the Mediterranean.
Many marine species host these pesky parasites. Among these fish we find hake, bonito, cod, sea bream, anchovy, and so on. Special case is the species that are consumed raw, smoked and marinated, such as anchovies, sardines, mackerel, herring and salmon. Within crustaceans, crabs and lobsters; octopus and squid in cephalopods. It is generally found in the belly (very present in restaurants) and the abdomen area.
Freshwater fish are spared from these parasites. Here we find, for example, trout and carp. Cockles, oysters, clams and mussels do not have Anisakis either.
Consequences of Anisakis food poisoning
Anyone suffering from Anisakis poisoning may react with an allergy or gastroenteritis. Symptoms, in both cases, can last for up to several days. We also tell you that not all people feel the symptoms of anisakiasis; many simply have a mild stomach upset that, after a few days, evaporates. But humans are not the ultimate host for these parasites because Anisakis larvae cannot survive in the body and end up dying. That is why many of the anisakiasis are asymptomatic or have mild reactions.
The allergy begins minutes or hours after the ingestion of the infected food. In milder cases, the person has hives and irritation, difficulty breathing; in the most serious cases, asthma and anaphylactic shock. We tell you that only 10% of cases have allergy symptoms .
The episodes of gastroenteritis, which we all know so well, appear 1 or 2 days after ingesting the parasites. There are vomiting, stomach pain, nausea, diarrhea, constipation and, in the most severe cases, intestinal obstruction; this can lead to the death of the patient.
How to prevent Anisakis infection
Fish is a fundamental food in a healthy diet. You are not going to stop consuming it because of the risk of contracting an Anisakis infection, but we do recommend that you be very careful when cooking fish.
The first thing is to gut the fish as soon as you take it home. You can even ask the fishmonger to make it for you. This will prevent parasites from moving towards the muscles. On the other hand, if you are going to eat raw or rare fish, it is advisable to freeze it for 5 days at -20º C. As home refrigerators do not reach these temperatures, many advise freezing it for more days before consuming it. If you don’t have time, industrially frozen fish is safer and parasite-free.
Anisakis, not only enter the body by eating raw fish. Cooking it at low temperatures also increases the risk. It is recommended to cook the fish at 60ºC, for at least 2 minutes, particularly if it is fresh and recently bought fish, without freezing. We tell you that putting it in the microwave is not very helpful, because the temperature is not enough.
Diagnosis and treatment
As you have already noticed, Anisakis infection presents quite common reactions to other types of diseases and parasites. Leaving aside the most severe cases, the first symptoms appear 24-48 hours after eating fish. This is when you should sound your alarm bells and consider infection by these parasites.
To confirm the diagnosis, 2 types of tests can be done. The doctor may order a blood test (serology) to detect antibodies against certain antigens. Among these we find the Prick test or allergy skin test; In this, an allergic reaction is reproduced in the dermis to determine the allergen.
When faced with anisakiasis, doctors can also request X-rays. Through radiological tests it is detected if a narrowing of the intestines can occur, for example. Infection can also be diagnosed through endoscopy; this test also serves as a treatment to remove the parasite. With endoscopy the doctor will see the anisakis in all their splendor.
Treatment is usually quite simple as most cases respond immediately. The infection generally clears up on its own and without complications. Medications are usually prescribed to ease stomach discomfort and relieve vomiting and diarrhea, if you have them. If the intestine is inflamed, the doctor may order corticosteroids to avoid surgery.
In case of allergies, antihistamines or corticosteroids are enough. If the allergic reaction is severe and anaphylactic shock occurs, adrenaline should be applied immediately.
