Anisakidoz - Causes, symptoms and treatment. MF.

Anisakidosis is a fairly recent problem in parasitology. This disease began to manifest itself most clearly from the middle of the XX century, when in 1955 in the Netherlands for the first time the first case of human infection after eating salted herring was registered.

For a long time, the disease was considered to be of little danger for humans, since it was established that the worm larvae do not develop in the human body before the mature stage. However, it soon became known that larvae in themselves are not only not harmless, but they also lead to serious health disorders of the sick person, and in the absence of assistance, even grave consequences.

Anisakidosis is a parasitological disease caused by larvae of helminths from the family Anisakidae, characterized by the predominant development of the pathological process in the gastrointestinal tract.

Geographic spread of anisakidosis

Along with the Netherlands, this helminthiasis is registered with a certain frequency in many European countries( Great Britain, France, Belgium, Sweden, Norway), South and North America, Southeast Asia( China, Korea, Japan and others).Rarely, but this disease occurs among the inhabitants of Russia - the Central Region, the Far East, Kamchatka and others.

In connection with the increase in consumption of the world's population of salted salmon products, and sometimes in raw and semi-raw form, a certain level of disease is maintained in almost any territory for which these products can be imported from different countries. A number of literature sources on the basis of a study of a large fish population indicate the high invasiveness of almost 100% of Pacific herring from the coast of Japan, 50% of hake in the same region, 25% of cod, up to 35% of pollock, up to 30% of mackerel and putasu and severalfish of other species. Such data should alert the person with respect to the rules for the thermal treatment of this product and limit the consumption of raw or semi-raw fish products.

Causes of occurrence of anisakidosis

The causative agent of anisakidosis is the larval stage of helminths belonging to the Anisakidae family, the genus Anisakis - Anisakis simplex( herring worm), the genus Pseudoterranova - Pseudoterranova decipiens, the genus Phocanema( codworm), the genus Contracaecum, the genus Hysterothylacium and others,the name "Anizakidy".These are small nematodes, whose body is spindle-shaped with rounded ends, measuring up to 65 mm in females and 55 mm in males. The head of the worm has lips in the number of 3 pieces. Fertilized females produce eggs, which for further development must enter the environment and into the organism of the intermediate host. Parasitological effects on humans are provided by the larvae of anisakid. Anisakid larvae are thermally moderately resistant - withstand a temperature of + 45º, at a temperature of + 60º perish within 10 minutes. When frozen to -18 °, the larvae die only after 14 days, at -30 ° they die within 10 minutes.

Sources of infection. The final masters of anisakids are marine mammals( for example, cetaceans - whales, dolphins, as well as pinnipeds - fur seals, seals), some sea fishes - stingrays, sharks, and in some cases birds feeding on fish - herons, pelicans. It is in the gastrointestinal tract of the final host that the sexually mature females and males of anisakids parasitize.

Intermediate hosts can be fish of freshwater and salt water bodies, crayfish, mollusks.
There are additional hosts of anisakids, which can carry larvae - a number of marine fishes - sea bass, cod, flounder, hake, sea trout, mackerel, capelin and many others.

Herring - a source of infection with anisakidami

The cycle of development of anisakid. After fertilization, eggs enter the environment, namely into water bodies. Here larvae emerge from the eggs, which fall into the intermediate hosts( mollusks, crustaceans, some fish), in the organism which can be found both simple larvae and cysts( larvae surrounded by a capsule).Invasiveness of fish by larvae reaches up to 1000 per fish. Larvae reach a length of 3-4 cm, have a pale yellowish appearance, sometimes with a brownish tinge( depending on the type of pathogen).Cysts are rounded formations( the larvae are arranged in them in the form of a spiral) with a translucent capsule around. Infected larvae are musculature of fish, internal organs( liver and gallbladder, intestine), body cavity of hosts. Ultimate hosts become infected by eating small fish, crustaceans and mollusks, invasive larvae of anisakid. After catching fish, larvae from the digestive system very quickly penetrate into the internal and musculature, which is why early cutting of freshly caught fish is very important( see prevention).

The mechanism of human infection is fecal-oral, and the way is food. A person becomes infected by eating heat-poorly processed invasive marine fish, crustaceans, mollusks( that is, containing larvae in a viable state). In the risk group, lovers of eating raw or not enough smoked, not enough salted fish, eating caviar "five-minute" and so on. Certain customs in culinary preferences may contribute to infection with anizakid, for example, caviar of weak salting, cooking "he" from raw fish, various national dishes, sushi, sashimi.

Food that can be contaminated with anisakid

Pathogenic effect of anisakid on the human body

After ingestion of invasive fish and seafood larvae, larvae enter the mucous membrane of the stomach, small and large intestines, and sometimes the pharynx. Sexually mature individuals do not develop, the duration of infestation lasts from several weeks to 3 months.

1) Due to the larvae, mechanical damage to the mucous membrane of the digestive system occurs with the formation of inflammation, swelling of the mucosa, "granulomatous eosinophilic infiltrates" or granulomas. Granulomas are morphologically - a larva, edema and an inflammatory infiltrate with hemorrhages.

2) Possible development of intestinal obstruction due to granulomas formed, as well as perforation of the intestinal wall with the development of peritonitis.

3) Sensitization of the body by the products of the vital activity of anisakid( similar to the action in toxocarosis) is an allergic reaction of the body, manifested as urticaria, toxic-allergic edema, bronchospasm.

Clinical symptoms of anisakidosis

The incubation period( from the time of infection to the appearance of the first complaints) can be
up to 1-2x weeks. The whole clinical picture is largely determined by the location of the larvae. At the onset of the disease, when there are symptoms in the lumen of the intestine, there may not be any symptoms.

The gastric form of anisakidosis ( the introduction of larvae into the wall of the stomach) is the most common
.Patients complain of pain in the epigastric region( areas of the stomach), often acute nature, unstable, nausea and vomiting, periodically vomiting with blood veins. Almost simultaneously, patients develop a severe allergic reaction according to the type of urticaria, toxic-allergic edema and others. Often the symptoms are accompanied by a temperature reaction, and the fever can be high - over 38º.
A reverse( or retrograde) drift of larvae from the stomach into the esophagus and pharynx is possible, in which case patients are disturbed by coughing, swelling in the throat, sometimes soreness behind the sternum.

The intestinal form of anisakidosis is accompanied by the appearance of abdominal pains in the near-bulbous
area, the iliac regions, more to the right, where the pains can be acute, intensive, and therefore an "acute abdomen" should be excluded by the surgeon. Pain is accompanied by flatulence, a feeling of increased bubbling in the abdomen( rumbling), a stool breaking from mushy to watery. Sometimes streaks of blood, mucus appear in the stool.

The disease can be acute, subacute and chronically. The course of the disease can be either mild, moderate or severe. In severe form complications occur.

Complications of anisakidosis

Intestinal obstruction, perforation of the intestinal wall with the development of peritonitis, and in the absence of timely assistance and death.

Diagnosis of anisakidosis

Diagnosis is made on the basis of the data set:

1) Epidemiological anamnesis - the availability of seafood( herring, cod and others) and seafood( squid, crustaceans) is not thermally processed or in raw and semi-endemic territory for anisakidosis and consumption of seafood there.
2) Clinical data are symptoms characteristic of the gastric or intestinal form of the disease in combination with an allergic reaction in the past or present. In view of the nonspecific symptoms of the disease, differential diagnosis will need to be carried out with a variety of digestive system diseases: gastritis, gastric and duodenal ulcer, gastroenteritis, Crohn's disease, oncological processes, pancreatitis, cholecystitis, appendicitis, diverticulitis and others.
3) Laboratory studies:
- Detection of larvae of anisakid in vomit masses and stools of patients is a rather rare method of detection, most often neither larvae nor helminth eggs are detected with microscopy;
- Instrumental diagnostics: FGDS( fibrogastroduodenoscopy) allows to identify edema and erosion of the mucous membrane in places of introduction of larvae, and sometimes to remove the larvae;contrast fluoroscopy.
- Surgical intervention with resection of the stomach or part of the intestine allows revealing the penetrated anisakid;
- In a general blood test, you can identify leukocytosis, eosinophilia.
- Serological methods have no practical application.

Anisakidosis - larvae in the mucous membrane of

Treatment of anisakidosis

Therapeutic measures for anisacidosis are as follows:
1) Surgical intervention by minimally invasive methods or by usual methods that is possible if appendicitis, intestinal obstruction, perforation of the intestine, ie in case of complications, arises. During the operation, larvae are often removed with the help of an endoscope, however, one should watch for their complete removal, since the remaining head end can lead to the appearance of new granulomas.

Anisakidosis - removal of larva

2) Drug therapy is performed by antiparasitic drugs( mebendazole, albendazole) in short courses, at which a positive therapeutic effect is noted.

Prognosis of the disease is severe in the event of complications and lack of timely resuscitative care.

Clinical follow-up is established after an operative intervention during the year with the FGDs once every 4-6 months.

Prevention of anisakidosis

- Observance of a food culture( eating only proven thermally processed fish and seafood, avoiding the consumption of raw or low-salted fish).
- Compliance with the rules for handling suspicious marine fish and seafood. The rules include the rapid evaporation of fish to prevent the rapid introduction of anisakid larvae into the musculature of fish, fish freezing at a temperature of -20º for at least 120 hours( 5 days), and at -18º for 14 days;thermal processing of fish( at a temperature of +80º and more, 20 minutes are enough to kill the larvae);sufficient salt of fish - salt concentration of 14% for 10-12 days.
- Compliance with the rules for cutting fish( separate knife, board and utensils).
- Helminthological examination of sea fish and seafood.

The doctor infektsionist Bykova N.I.