Even after cooking, Anisakis spp. still pose a health risk to humans. Anisakids (and related species such as Pseudoterranova spp. and Hysterothylacium aduncum) release a number of biochemicals into the surrounding tissue when they infect fish. They are also often consumed whole, incidentally, within the flesh of the fish.
7. Allergic reactions & Risk of anaphylactic shock
Even after cooking, Anisakis spp. still pose a health risk to humans. Anisakids (and related species such as Pseudoterranova spp. and Hysterothylacium aduncum ) release a number of biochemicals into the surrounding tissue when they infect fish. They are also often consumed whole, accidentally, within the flesh of the fish. Larvae in the body cavity of herring, humans are susceptible to nematodes, can develop disease and have severe anaphylactic reactions after eating fish contaminated with Anisakis spp. This is often confused with an allergy to a fish or shellfish (clams, oysters, mussels, crabs, shrimps), Anisakids allergy components are often difficult to test for because diagnostic kits often produce positive cross‐reactions when tested with other allergens.
Diagnosis in humans: In cases where the patient vomits or coughs up worms, the disease can be easily diagnosed by the morphology of the roundworm (it should be noted that Ascaris lumbricoides, a large roundworm in humans and a terrestrial worm related to the anisakines, and the larvae sometimes crawl up into the nasopharynx). Other cases may require the use of an endoscope that allows the physician to examine the stomach and the first part of the small intestine. These instruments are equipped with forceps that can be used to remove worms from that organ. Other cases are diagnosed based on histological examination of the main lesion, which is a granuloma, through abdominal exploration. A test that is also commonly used, especially the radioallergosorbent test for anasakiasis, is not commercially available.
The authors, Sung‐Jin Choi, Jae‐Chun Lee, Moo‐Jung Kim, Gyu‐Young Hur, Seung‐Youp Shin, and Hae‐Sim Park, who are from the Department of Allergy and Rheumatology, Ajou University College of Medicine, Suwon, Korea; Department of Internal Medicine, Jeju National University, Korea; and Department of Otorhinolaryngology, Kyunghee University College of Medicine, Seoul, Korea, conducted a study that showed that Anisakidae larvae can cause Anisakiasis when ingested by humans. Although several groups have reported allergic gastrointestinal Anisakis disease in Spanish and Japanese subjects, the present report is the first to summarize the clinical features of 10 cases of allergic Anisakis infection in Korea. A total of 10 Korean patients (6 men and 4 women) complained of severe allergic reactions after ingestion of raw fish or seafood. Anisakis sensitization is determined by the detection of Anisakis simplex‐specific IgE antibodies in the serum of patients.
The most common clinical features of Anisakiasis are pruritus and urticaria (100%), followed by abdominal pain (30%) and anaphylaxis (30%). All symptomatic patients also exhibited high levels of serum IgE antibodies (0.45‐100 kU/L) to A. simplex . Nine out of 10 patients (90%) showed atopy and very high serum IgE levels. Fish species suspected of being contaminated with Anisakis species were flatfish (40%), sardines or eels (40%), squid (30%), sea snails (10%), and tuna (10%). Anisakis simplex should be considered a food allergen in adults who present with urticaria, angioedema, and anaphylaxis after consuming raw or undercooked seafood.
The development of food allergies is increasing in relation to food consumption worldwide. In the United States, approximately 6% of infants and young children and 3.7% of adults exhibit some degree of allergic reaction to some food. The main foods for children are cow’s milk, eggs, peanuts, wheat, beans, fish, and shellfish such as shrimp, crab, clams, oysters, and mussels are at the top of the list. Anisakis simplex is a roundworm of the order Ascaridida , family Anisakidae , subfamily Ascaridoidea . Any fish or mollusk can be parasitized by the third‐stage larvae of Anisakis. Mackerel, cod, sardines, tuna, and squid are also among the species most susceptible to the parasite. Ingestion or ingestion of the third‐stage larvae of Anisakis can cause Anisakiasis in humans. Symptoms of Anisakiasis increase as the worms penetrate the gastric mucosa, leading to abdominal symptoms and allergic reactions.
Van Thiel et al. (1960) reported the first case of Anisakiasis in the Netherlands in 1960. Subsequently, many cases were reported in Japan and Western Europe where raw fish is commonly consumed. Kim et al. (1971) also reported a case of Anisakis larvae in the pharynx of a human as the first case in Korea. Subsequently, several patients with acute Anisakiasis and mainly gastrointestinal symptoms such as abdominal pain, nausea, and vomiting were analyzed and clarified through gastroduodenoscopy. Desowitz et al. (1985) described a method for detecting specific IgE antibodies against A. simplex. Since then, Kasuya et al. have also identified the allergenic potential of A. simplex in 2 clinical cases and have emphasized this parasite as the causative agent associated with raw fish consumption in patients with urticaria. In Korea, Kim et al. reported the first case of Anisakiasis with gastrointestinal allergy after the patient ate raw fish on Jeju Island. There have been no reports of allergic reactions due to Anisakis, although Korean people freely eat raw fish.
8. Complications and effects on the human body
Anisakids pose a health risk to humans in two ways: through infection with worms from improperly handled or raw fish and through allergic reactions to chemicals released by infected fish parts. Sung‐Jin Choi et al., Department of Allergy, Ajou University of Medicine, Korea; Department of Internal Medicine, Jeju National University (Korea); Department of Otorhinolaryngology, Kyunghee University of Medicine, Seoul, conducted a study that showed that Anisakis có thể gây bệnh khi người ăn phải chúng. Dù một số nhóm nghiên cứu đã báo cáo về dị ứng trong bệnh Anisakis trên đường tiêu hóa ở người Tây Ban Nha và Nhật Bản, song báo cáo ở đây là lần đầu tiên tóm lượt các đặc điểm lâm sàng của 10 ca nhiễm Anisakis tại Hàn Quốc, 6 nam và 4 nữ có triệu chứng dị ứng nghiêm trọng sau khi ăn cá sống hoặc thức ăn cá hay mực từ môi trường biển. Sự mẫn cảm với Anisakis spp. được xác định bằng phát hiện kháng thể IgE đặc hiệu với A. simplex trong huyết thanh bệnh nhân. Đặc điểm lâm sàng hay gặp nhất của bệnh nhân là ngứa, mày đay (100%), đau bụng (30%) và sốc phản vệ (30%).
All symptomatic patients showed high levels of serum IgE antibodies (0.45‐100 kU/L) to A. simplex . Nine out of 10 patients (90%) had atopic manifestations and elevated serum IgE levels. Fish species suspected of being infected with Anisakis species were flatfish of the order Pleuronectiformes (40%), sardines or eels (40%), squid (30%), sea snails (10%), and tuna (10 %). A. simplex should be considered a food allergen in adults who present with urticaria, angioedema, and anaphylaxis after ingestion of raw or undercooked seafood.
The development of food allergies is increasing in relation to food consumption worldwide. In the United States, approximately 6% of infants and children and 3.7% of adults exhibit some degree of allergic reaction to some food. The main foods for children are cow’s milk, eggs, peanuts, wheat, beans, fish, and shellfish such as shrimp, crab, clams, oysters, and mussels are at the top of the list. A. simplex is a roundworm and any fish or mollusk can be infected with the third‐stage larvae of Anisakis spp. Mackerel, cod, codfish, anchovies, sardines, tuna, and squid are also susceptible to the parasite. Ingestion or ingestion of the third‐stage larvae of Anisakis spp. can cause Anisakiasis in humans.
Anisakiasis symptoms increase as the worms penetrate the gastric mucosa, leading to gastrointestinal symptoms and allergic reactions. Subsequently, some cases of acute Anisakiasis and mainly gastrointestinal symptoms such as abdominal pain, nausea, vomiting were analyzed and clarified by gastroduodenoscopy. Desowitz (1985) described a method for detecting specific IgE antibodies against A. simplex. Differential symptoms when infected with parasites due to eating raw fish: small liver flukes Clonorchis sinensis, Anisakis spp. and tapeworms Diphyllobothrium spp . All of these agents when infected can cause gastrointestinal symptoms, but differentiation is very difficult. Within a few hours after ingestion of infected larvae, the virulent abdominal pain caused by the worms is accompanied by abdominal pain, nausea, vomiting. Sometimes the larvae cause us to cough. If the larvae pass through the intestinal wall into the small intestine, a severe granulomatous and eosinophilic reaction may also occur 1‐2 weeks after infection.
Diagnosis can be established by gastroscopy revealing 2cm long larvae, which can be removed, or by histological analysis and examination via biopsy or during surgery. It is thought that the risk is higher if we eat wild rather than farmed fish infected with Anisakis spp. Many countries require that potentially dangerous fish intended to be eaten raw be frozen to kill the parasites.
Some severe cases of Anisakiasis are often very painful, requiring surgical intervention. Removal of the worm from the lesion is known to be the only way to relieve pain and eliminate the cause (rather than waiting for the worm to die). Symptoms may also persist after the worm has died because some lesions found during surgery to remove the worm have retained worm remnants. Pyloric stenosis has also been noted in laparotomy to remove worms from the stomach. For worms, humans are the definitive host, Anisakis and Pseudoterranova larvae cannot survive in humans and even die. Therefore, treatment in symptomatic cases, heavy doses of infection. Caution should be exercised when prescribing treatment in cases of small bowel obstruction due to Anisakis larvae , such cases require emergency surgery, although there are some cases where treatment with Albendazole alone (avoiding surgery) has been successful, but it should not be risky.
With the clinical manifestations and complications that can threaten the patient’s life due to this dangerous parasite, we should be cautious and advise the community to always be careful, and can communicate behavior change to help the whole community know how to practice safe eating to avoid infection with parasites in general and Anisakis in particular.
9. Detection & Diagnosis of diseases caused by Anisakis spp.
Anisakiasis spp . known to infect humans include the Anisakis simplex complex [ A. simplex sensu stricto, A. pegreffii, A. berlandi (= A. simplex C)], the Pseudoterranova decipiens complex ( P. decipiens sensu stricto, P. azarasi, P. cattani and others) and the Contracecum osculatum complex . Recent genetic studies have shown high genetic diversity among these Anisakis groups and have suggested that additional wild species (cryptic species) may also cause zoonotic infections.
Diagnosis of Anisakiasis is not easy due to the lack of specific symptoms.
Anisakiasis is generally referred to in relation to acute human disease where it is suspected. Some conservative authors have given the disease a different name to refer to it, but it is largely considered familial. The clinical spectrum is diverse with many symptoms independent of the Anisakis spp. species as reported in some cases. A history is necessary (Del Rey‐Moreno, 2008) to establish dietary implications within 72 hours before the onset of symptoms such as acute gastritis, epigastric pain and abdominal pain, such as a history of eating sea fish, or seafood preserved in vinegar, or in brine or drying seafood in salt is not sufficient to cook and cannot kill live Anisakis spp. larvae.
In North America, Anisakis spp. is usually diagnosed when the infected patient feels a prickling or tickling sensation in the throat and coughs or can remove the worms by hand when coughing. In more severe cases, there will be acute abdominal pain similar to acute appendicitis accompanied by nausea. Symptoms occur from one hour to several weeks after infection with the pathogen in undercooked vegetables or seafood. The roundworms can revive in the patient, with their anterior end, these larval roundworms of worms from fish or shellfish such as clams, mussels, shrimp, crab, … they usually burrow in the digestive tract to the muscular mucosa (sometimes they also penetrate the intestinal wall perfectly and we can find them in the body cavity. They produce substances that can attract eosinophils and other blood cells of the host to this infected area.
‐ In cases where the patient vomits or coughs up worms, the disease can be easily diagnosed by the morphology of the roundworm Anisakis spp;
‐ Diagnosis can be established by gastroscopy detecting larvae in the upper part of the small intestine, and Anisakis spp. larvae can be obtained;
‐ Histological analysis and testing through biopsy or during surgical biopsy using larval graspers;
‐ Some cases are diagnosed based on histological analysis of the main lesion, which is granuloma, through abdominal exploratory surgery;
‐ A commonly used radioallergosorbent test for the diagnosis of Anasakis spp. disease is also of interest.
Method for detecting Anisakis spp. parasites in fish and squid
‐ The new method allows the detection of Anisakis in any fish product, from whole, fresh or frozen fish to canned fish. Developed by Spanish scientists, the detection system is based on molecular techniques and overcomes the limitations of the classical method. The method is characterized by high specificity and high sensitivity in detection even when they are present at very low concentrations (0.05 pg) of Anisakis spp. , Pseudoterranova spp. , Contracaecum spp. and Hysterothylacium spp. in the analyzed sample.
‐ This method is fast and efficient and, unlike previous techniques, can be applied to any fish product regardless of the degree of product variability. The methods used to date for the detection of Anisakis spp. larvae are visual inspection and digestibility by artificial gastric juice. The classical methods are not applicable to very large species or to processed products;
The species of parasites that infect humans are usually Anisakis simplex , Pseudoterranova decipiens and less commonly Contracaeum osculatum and Hysterothylacium aduncum . The presence of Anisakis larvae parasitizes the muscle tissue and viscera of many species of fish and molluscs. Affected fish species are cod, black cod, horse mackerel, sardines, anchovies, herring, salmon, tuna, whitefish, flounder and pollock, while affected cephalopods are squid and cuttlefish.
‐ Conduct seafood testing to detect and collect Anikasis spp. larvae by biopsy and microscopic examination. Early detection of worm larvae in seafood will help with research , teaching and recommendations for safe food use and good nutrition .
‐ Testing fish food on a clean, bright table used for processing or handling reduces the number of worms in some white fish known to be commonly infected. This method is not completely effective, nor is it effective enough to remove large numbers of worms in fish.
‐ The technician must be qualified and professionally trained in testing or have a testing certificate, trained in professional procedures in this field. In terms of materials and chemicals, biological products for diagnosis include: Xylene glass cleaner , 0.9 % NaCl , 70% ethanol , 99 % ethanol , acid for immersion , distilled water. Tools include a knife , a plastic cutting board, a sample container, a specimen box , a pointed stainless steel needle , a 75 x 25 mm glass slide, absorbent paper, a medical mask, a medical glove, a 3cm ‐ 5cm petri box , a plastic pipet ;
‐ Equipment: stereoscopic magnifying glass, optical microscope with 10X eyepiece, 10X and 40X objective lens, incubator, refrigerator, biosafety cabinet level II.
‐ Prepare the subject or specimen including fresh seafood or refrigerated at 2 o C ‐ 8 o C for less than 10 days. The time to perform the technique can be 2‐4 hours in the laboratory and in the field .
‐ Laboratory technicians must wear medical protection when in contact with specimens such as: gloves, masks, hats, and lab coats. Comply with biosafety conditions in the laboratory. Samples after analysis, excess samples, and samples after testing must be processed to ensure biosafety. Instruments must be processed after testing in accordance with biosafety regulations .
‐ Start the biological safety cabinet at least 15 minutes before performing , arrange the necessary tools in the biological safety cabinet ;
‐ Record the seafood code, identify the seafood species XN, seafood collection source, collection address. Use a knife to thinly slice the seafood about 5cm x 2cm long, 0.5mm thick and place on a glass slide ;
‐ Use another slide, place it on the slide with the cyst and gently press the 2 slides together . Observe and find A nisakis spp. larvae under a magnifying glass or microscope at 10x objective and identify them at 40x objective.
‐ When larvae are observed, separate the upper glass slide, use a stainless steel needle to separate and concentrate the larvae. Suction the larvae with a plastic pipette.
‐ Separate and concentrate the larvae (suck all the larvae with a Pasteur pipette and transfer to a 3cm ‐ 5cm Petri dish). Count the number of larvae in the Petri dish and record it on the result sheet.
10. Treatment & Handling Attitude
Some severe cases of Anisakis spp. are very painful and require surgical intervention. Removal of the worms from the lesions is the only way to relieve pain and eliminate the agent.
Symptoms may persist after the worms have died, as some lesions found during surgery to remove the worms may contain remnants of the worms. In the definitive host, humans are the host, and Anisakis spp. and Pseudoterranova spp. larvae do not survive. Therefore, treatment of symptomatic cases with high infection doses is necessary. Caution should be exercised in treating small bowel obstruction caused by Anisakis spp. larvae, which may require emergency surgery, although treatment with albendazole alone (avoiding surgery) has been successful in some cases.
Impact on human health
Since 1960, Van Thiel and colleagues reported the first case of Anisakis spp. infection in the Netherlands, then more and more cases were reported in Japan, Korea, and Western Europe because of the daily consumption of raw fish (Desowitz et al., 1985). Anisakis spp. pose a health risk to humans, when the disease develops, it is called Anisakiasis and it causes damage to humans in two ways: (i) Through infection with worms from improperly handled or live fish and (ii) Through allergic reactions to chemicals secreted by the flesh of infected fish (Sung‐Jin Choi et al., 2014).
Studies have shown that Anisakis spp. larvae can cause disease when ingested. Regarding allergic reactions to Anisakis spp. in the gastrointestinal tract, patients from Spain, Korea and Japan reported severe allergic reactions after ingestion of raw fish or seafood. Sensitization to Anisakis spp. was confirmed by the detection of specific IgE antibodies to Anisakis spp. in the serum of patients and the most common clinical features of the disease were pruritus, urticaria (95‐100%), abdominal pain and gastrointestinal disorders (17‐31%) and anaphylaxis (30%). Given the high incidence of anaphylaxis, vigilance against this species is necessary. All patients who showed symptoms also expressed high levels of blood IgE antibodies (0.45‐100 kU/L) to A. simplex.
In these studies, the authors also identified fish species suspected of being contaminated with Anisakis spp. as sardines, eels (40%), squid (30%), sea snails (10%), tuna (10%) and identified Anisakis simplex as a food allergen in patients with urticaria, angioedema, and anaphylaxis after ingestion of raw or undercooked seafood. The development of food allergies is increasing in relation to food consumption on a global scale. In the United States, approximately 6% of children and infants and 3.7% of adults exhibit some degree of allergic reaction to some foods. The main foods in children are cow’s milk, eggs, peanuts, wheat, beans, fish, and shellfish such as shrimp, crab, clams, oysters, and mussels are the top foods on the list.
Any fish or mollusc can be infected by the third‐stage larvae of Anisakis spp. Mackerel, cod, anchovies, sardines, tuna, and squid are also susceptible to the parasite. Ingestion or ingestion of third‐stage larvae of Anisakis spp. can cause Anisakiasis in humans.
Symptoms of the disease increase when the worms penetrate the gastric mucosa, leading to abdominal symptoms and allergic reactions. Next, some patients have acute infections and mainly present with gastrointestinal symptoms such as abdominal pain, nausea, vomiting and lesions on gastroduodenoscopy. The symptoms need to be differentiated from infections with parasites caused by eating raw fish (small liver flukes Clonorchis spp. and fish tapeworm Diphyllobothrium spp.). All of these agents when infected can cause gastrointestinal symptoms, so differentiation is very difficult. Within a few hours after ingestion of larvae, acute abdominal pain occurs due to worms accompanied by nausea, vomiting, sometimes the larvae cause cough. If the larvae pass through the intestinal wall into the small intestine, a very severe granulomatous and eosinophilic reaction forms and can also occur 1‐2 weeks after infection, or can cause symptoms similar to Crohn’s disease.
Anisakis is a parasite that often causes allergic reactions.
The European Food Safety Authority ( EFSA) has concluded that the parasites in fish products that cause allergic reactions in humans are anisakis larvae found in fresh fish. According to the report, European experts believe that consumers who eat fish products containing live anisakis larvae are more likely to have an allergic reaction than those who consume fish containing dead anisakis larvae. Refrigeration or heating can kill or inactivate the activity of this parasite.
EFSA confirmed that all fishing areas are contaminated with Anisakis spp. However, Atlantic salmon raised in floating cages or onshore tanks and fed live parasite‐free feed have a low risk of infection with Anisakis spp. EFSA has recommended that the European Union (EU) strengthen monitoring and diagnosis of allergic reactions to parasites in fish products and conduct research on other aspects such as the life cycle of the parasite, its geographical distribution and its widespread role. In addition, to reduce allergic reactions, ESFA emphasizes the need to inform health professionals, fish workers and consumers about the dangers of this parasite and how to eliminate it.
Anisakis spp. is a nematode whose life cycle involves fish and squid and octopus and can produce allergic reactions when raw or undercooked infected fish are eaten. Anisakis spp. has a complex life cycle, passing through several hosts, with Anisakis spp. eggs laid in the sea and larvae eaten by crustaceans. Infected crustaceans are then ingested by fish and squid. The worms burrow into the intestinal wall and encyst in a protective shell, usually outside the internal organs, but occasionally in the muscles and under the skin. The cycle is completed when infected fish are eaten by marine mammals such as whales, seals and dolphins. The worms encyst in the intestine, grow, mate and release eggs into the seawater via the host’s feces.
Humans are infected by eating raw or undercooked fish
In some countries, Anikasis infection is common, such as Japan (from eating raw fish that has not been previously frozen), Scandinavia (from eating cod, mackerel, sardines containing the parasite), the Netherlands (from eating herring containing the parasite), and parts of South America (from eating raw fish marinated in lemon as an appetizer). Others may be caused by eating squid or cuttlefish containing the parasite. Anisakis spp. infection is also uncommon in lakes and fish farms or fish raised in low‐salinity water conditions.
Anisakis spp. still pose a health risk to humans. Anisakis spp. release a number of biochemicals into the surrounding tissue when they infect fish. Because they are located in the flesh of the fish, they are also often consumed whole. Humans are susceptible to these worms, and can develop disease and severe anaphylactic reactions after eating fish contaminated with Anisakis spp. This is often confused with an allergy to a fish or shellfish, and Anisakis spp. allergy is difficult to test for because diagnostic kits often cross‐react with other allergens.
(continuted)
Author: Dr. Huynh Hong Quang
(Quy Nhon Institute of Malaria, Parasitology and Entomology)
