What is Anizacidosis?
Anisacidosis (synonyms: anisacidosis – Russian, anisakiasis – English, anisakiase – French) – zoonotic helminthiasis and characterized by lesions of the gastrointestinal tract, caused by parasitizing the larval nematode stages of the Anisakidae family in the human body.
In humans, parasitization of nematode nematodes of the genus Anisakis (herring worm), Phocanema (cod worm), and others causes an acute disease with severe allergic symptoms. Anizakioz is registered in America, Japan, the Netherlands. In all countries, the pathogen is parasitic in fish from freshwater, brackish and saline bodies of water.
Causes of Anizacidosis
The causative agents of human anisacidosis are the larval stages of development of the helminth of the genera: Anisakis, Contracaecum, Pseudoterranova, Hysterothylacium, belonging to the order Ascaridida Skrjabin et Schikhobalova, 1940, the family Anisakidae Skrjabin et Korokhin, 1945, The final owners of these helminths are many marine mammals (cetaceans, pinnipeds), carnivorous marine fish and fish-eating birds, in the gastrointestinal tract of which males and anisakids are parasitic. The average length of females is 60-65 mm, males – 50-55 mm. The body is spindle-shaped, narrowed to both ends (more narrowed to the head end). On the head end there are three lips.
Fertilized eggs fall into the water, where a larva leaves them, which is swallowed by the first intermediate hosts, crustaceans, from the composition of krill, most often belonging to the family Euphausiidae.
As additional owners many sea fishes, mollusks, larger crustaceans feeding on small crustaceans serve. Anizakid larvae in the body of intermediate hosts localize in the body cavity, on the surface or inside the various internal organs and in the muscles of the fish. They are inside translucent capsules – cysts, or without them. The size of cysts on average is 3-7 × 1-2 mm. Anisakid larvae that are not encystized, for example P. dicipiens, have a length of 1.5 to 6 cm.
Infection of final hosts occurs when they eat infected intermediate hosts: fish, crustaceans and mollusks. If larger intermediate hosts feed on smaller ones that are invaded by the larvae, then these larvae accumulate in the body of a larger, predatory fish.
Pathogenesis during Anisacidosis
People become infected by eating raw, pickled or lightly salted fish delicacies, such as green herring, sushi, sashimi, sunomono, chinook and gravlax, which contain larvae of stage III development. Invasion can be asymptomatic and is detected only when the helminth is released when coughing or with vomit masses. However, more often the larvae of the pathogen penetrate the mucous membrane of the stomach, small or, more rarely, large intestine.
Here they produce eosinophilic granulomatous tumors with edema, thickening and induration of the intestinal wall, which can be mistaken for gastric carcinoma or regional enteritis. Sometimes the larvae can penetrate the intestinal wall and cause damage to other organs of the abdominal cavity. Cases of intestinal perforation with peritonitis are also described.
In the pathogenesis of lesions developing in anisakiasis, as well as in toxocarosis, the leading role is played by sensitization of the body’s response to the antigens of the larvae. Morphologically, granulomas with a larva in the center, edema, hemorrhages in the mucous membrane of the gastrointestinal tract are found in the wall of the stomach and intestines.
When gastroscopy can be detected and in some cases removed the larvae from 2 to 4 cm in length, penetrated into the mucous membrane. The representatives of the Caucasoid race most often affects the small intestine.
Symptoms of Anizacidosis
The incubation period for anisacidosis is from several hours to 7-14 days. In many ways, the clinical picture of the disease is due to the location of the parasites. When the larvae are in the intestinal lumen, the symptoms can be very scarce. In gastric localization (the most common form of the disease), patients are worried about severe epigastric pain, nausea, vomiting, sometimes with blood. There is low-grade or febrile fever, the development of immediate-type allergic reactions (urticaria, angioedema).
In the case of the retrograde migration of anisakid larvae from the stomach to the esophagus, pain and irritation arise in the throat, cough. In intestinal anisaccosis, patients complain of pains in the navel and in the right iliac region, rumbling in the abdomen, flatulence. You may experience a symptom complex of acute abdomen, characteristic of appendicitis or intestinal obstruction.
Anisacidosis can be acute, subacute or chronic.
In mild cases of the disease, dyspeptic disorders (nausea, vomiting, abdominal pain) prevail. With severe invasion, paroxysmal abdominal pain occurs, sometimes symptoms of intestinal obstruction. Symptoms of a peptic ulcer or a tumor are often observed.
The clinical picture of anisacidosis can be quite severe and simulate the signs of an acute surgical disease of the abdomen. However, more often, colicy pains, diffuse tenderness of the abdomen, fever, and leukocytosis develop a week or more after eating fish. The disease usually spontaneously regresses on the background of conservative treatment.
Serious complications of intestinal anisacidosis include perforation of the intestinal wall and penetration of intestinal contents into the abdominal cavity with the development of peritonitis.
Diagnosis of Anisacidosis
The diagnosis is made on the basis of information about the use of raw herring, cod, clinical picture and morphological study of biopsy material. Sometimes the larvae can be found in the vomit or feces of the patient. At present, morphological identification criteria for anisakid larvae have been developed.
Helminth larvae can be detected by contrast X-ray and endoscopy or by examining areas of the stomach and intestines resected from surgical operations. When fibrogastroduodenoscopy, in the place of the introduction of helminths, swelling of the mucous membrane with multiple point erosion is detected. In the study of blood revealed moderate leukocytosis and eosinophilia. Serological diagnostic methods are not developed. When koproskopii larvae or anisakid eggs are not detected. Identification of the parasite to the genus and species is possible in the study of larvae removed by endoscopy or surgical intervention.
Anizakios should be differentiated from gastric ulcer and duodenal ulcer, gastritis, pancreatitis, cholecystitis and tumors. In the intestinal form, it is necessary to exclude appendicitis, diverticulitis, tumors, colitis and enterocolitis.
Treatment of Anisacidosis
Anisacidosis treatment is not developed. You can expect the effect of the use of mebendazole and thiabendazole. In cases of intestinal obstruction, the affected part of the intestine is resected. With timely treatment, the prognosis is good.
Preventive measures of anisacidosis include adherence to the correct technology of fish processing (quick gutting), keeping the fish in freezers at 20 ° C for 60 hours, proper cooking of the fish.