Alveococcosis

Alveococcosis is a disease associated with the entry into the body and development of the larvae of the tapeworm Alveococcus multilocularis.

ICD-10 code

B-67. Alveococcosis

Epidemiology

Alveococcosis is a disease with pronounced endemicity. Foci of the disease are observed in Germany (Bavaria and Tyrol), southern France, Alaska, northern Japan (Hokkaido Island), Azerbaijan, Armenia, Kyrgyzstan, Uzbekistan and Kazakhstan. In Russia, alveococcosis has been registered in Bashkortostan, the Kirov Region, Western Siberia, Yakutia (Sakha), Kamchatka and Chukotka. Mostly young people fall ill. Most often these are hunters, berry pickers, people involved in the dressing of animal skins and workers at fur farms caring for foxes and arctic foxes bred in cages. However, cases of the disease are known in small children under 5 years of age and in the very old.

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What causes alveolar echinococcosis?

Alveococcosis is caused by the tapeworm alveococcus. This is a flatworm measuring 2-6 mm in size, consisting of a head with four suckers and hooks, two or three segments, the last of which is occupied by the uterus, containing up to 400 eggs. Each egg is surrounded by a dense shell resistant to external influences and contains a larva of the parasite. The sexually mature worm parasitizes in the small intestine of the final hosts - red and black-silver foxes, arctic foxes, wolves and corsacs. The number of worms in the body of one animal can reach several tens of thousands. The parasite's eggs naturally enter the environment, where they are eaten by the intermediate hosts of alveococcus - mouse-like rodents (field mice, gophers, lemmings, gerbils, river beavers and nutria). The final hosts become infected by eating the intermediate hosts, and the development cycle of the alveococcus in nature is completed. After eating the intermediate hosts, the final hosts develop sexually mature worms in the body of the latter by the 22nd-42nd day.

A person becomes infected by accidentally eating alveococcus eggs. Under the influence of gastric juice, the egg shell dissolves, the released larva enters the blood and is carried to the liver. Since the size of the alveococcus larva significantly exceeds the diameter of the human liver capillaries, it almost always lingers there and begins to develop. The larva turns into a small bubble with a diameter of 2-4 mm and actively reproduces by budding. Thus, a parasitic "tumor" appears, consisting of many small parasite bubbles located in the connective tissue stroma of the liver, which gives the parasitic "tumor" a very high density. The alveococcus node on the cut looks like porous fresh bread and consists of many chitinous parasite bubbles.

Unlike echinococcus, the parasitic node of alveococcus secretes the enzyme hyaluronidase, which melts the surrounding tissues. Thus, the node of alveococcus grows into the surrounding tissues and organs - the porta hepatis, diaphragm, lung, adrenal gland, kidney, pancreas, stomach, aorta and pericardium. The growth of alveococcus into the lymphatic and blood vessels leads to the fact that individual bubbles break off and are carried by the flow of lymph and blood to the regional lymph nodes, lungs and brain, where they also begin to develop, forming metastatic nodes. Individual bubbles of the parasite left in the liver during surgery also grow and provide relapses of the disease. This ability of alveococcus to grow into the surrounding tissues and organs, to metastasize and relapse makes alveococcosis very similar in its course to malignant tumors of the liver. The only difference is considered to be the slower growth of the parasitic node. Since the parasite feeds by diffusion of the host's nutrients, a more vigorous life reigns on the periphery of the node - alveococcus bubbles actively multiply and the node grows. At the same time, in the center, due to lack of nutrition, some parasitic elements die and decay cavities are formed - parasitic caverns. In most cases, they are filled with aseptic pus. In some cases, parasitic caverns break through into neighboring body cavities - abdominal, pleural and pericardium.

How does alveococcosis manifest itself?

The clinical picture of alveococcosis depends mainly on the stage of the disease and the complications present. The anamnestic data of patients with alveococcosis are quite characteristic. This is living in endemic areas. By occupation, these are most often agricultural workers, especially hunters, skinners, berry pickers and fur farm workers.

In the asymptomatic stage, patients usually do not complain of alveococcosis. There may be only allergic manifestations of the parasitic disease - urticaria and skin itching. In the uncomplicated stage, patients are bothered by constant dull pain and a feeling of heaviness in the right hypochondrium, a feeling of fullness in the stomach. During a physical examination, in most cases, hepatomegaly and local enlargement of the liver due to a parasitic node in it are noted. In this case, the node has a stony density.

When a parasitic cavern suppurates, pain in the right hypochondrium increases, hectic temperature, chills and profuse sweating appear. When the cavern breaks through into the body cavity, a violent picture of peritonitis or pleurisy develops.

The blockage of the liver gates leads to portal hypertension and mechanical jaundice. With portal hypertension, ascites appears, the veins of the abdominal wall are dilated, hemorrhoidal bleeding and bloody vomiting occur. When the bile ducts are compressed, the skin and sclera become yellowish, the urine darkens, the feces become discolored, and skin itching occurs.

When the cavities of decay break through into the abdominal cavity, sharp, sudden pain occurs and symptoms of increasing peritonitis appear. Breakthrough into the pleural cavity leads to the development of purulent pleurisy with respiratory failure, dullness of percussion sound and the presence of fluid in the pleural cavity.

Classification

Alveococcosis has three stages of progression:

• asymptomatic stage;
• uncomplicated stage;
• stage of complications.

Complications include: mechanical jaundice, portal hypertension, invasion into adjacent organs, bile-bronchial fistulas, breakthroughs of decay cavities into adjacent cavities, metastases, and atypical mask forms.

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Screening

Screening examination is advisable in endemic areas, especially among hunters and fur farm personnel caring for animals and participating in their slaughter. Clinical examinations, immunological reactions and liver ultrasound are recommended.

How to recognize alveococcosis?

Laboratory and instrumental studies

Alveococcosis is characterized by eosinophilia, which in some cases reaches significant levels, an increase in ESR, hypoalbuminemia and hypergammaglobulinemia. In advanced cases, the serum bilirubin content increases, and with the development of liver failure, the activity of transaminases increases. The Casoni reaction with echinococcal antigen in alveococcosis is positive in 90% of cases. This is explained by the genetic proximity of both parasites. The specificity of immunological reactions (complement fixation and hemagglutination) is quite high. With the development and introduction of new radiation research methods into widespread practice, these reactions have lost their dominant significance in the diagnosis of the disease.

The "gold standard" in the diagnosis of alveococcosis is currently considered to be ultrasound. During it, it is possible to determine the size, shape, topography of the parasitic node, its relationship with the elements of the liver gate and the inferior vena cava, and the presence of a parasitic cavern and sequesters in it. Doppler ultrasound allows you to detect the absence of blood flow in the area of the parasitic node and its increase around the existing "tumor" in contrast to the true tumor.

CT provides a huge amount of information. The increasing availability of this method of examination allows us to refrain from such complex and risky examination methods as arteriography and splenoportography. When X-raying on soft images in the shadow of the liver in half of the patients, calcification foci are determined in the form of "lime splashes".

Differential diagnostics

Alveococcosis is differentiated mainly from malignant liver tumors. In terms of clinical manifestations, both diseases are very similar. A significant difference is considered to be the dynamics of the process. In malignant tumors, the progression of the pathological process occurs quite quickly. In alveococcosis in adults, the disease proceeds relatively slowly. But when children are affected by alveococcosis, the pathological process is quite intense. Ultrasound examination and CT with biopsy allow to verify the diagnosis.

Epidemiological history (residence in an endemic area, occupation - hunters, fur farm workers), positive immunological reactions, eosinophilia in the peripheral blood, ultrasound and CT data help in determining the correct diagnosis.

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Example of diagnosis formulation

Alveococcosis of the liver. Stage: asymptomatic, uncomplicated, stage of complications (breakthroughs, mechanical jaundice, portal hypertension, bile-bronchial fistulas, metastases).

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How is alveolar echinococcosis treated?

Treatment goals

The goal of treatment is to remove the parasitic node, eliminate complications, or eliminate the most distressing symptoms of the disease in inoperable cases.

Surgical treatment

Drug treatment can be used only as an addition to surgical intervention or in an extremely serious condition of the patient. In alveococcosis, only liver resection within healthy tissues can cure a patient with alveococcosis. Due to the long asymptomatic course of the disease, operability is quite low and is, according to various authors, from 25 to 40%. In case of total liver damage, the only radical method of treatment is liver transplantation.

In severe cases of alveococcosis and the presence of a large parasitic cavity, a marsupialization operation is performed. In this case, the anterior wall of the decay cavity is excised, the cavity is emptied of contents and sequesters, and its edges are sutured to the edges of the wound. In this case, it is also possible to destroy part of the parasitic tissue using cryotherapy. Subsequently, partial rejection of the parasitic tissue through the wound and healing by secondary intention occurs. Subsequently, in a number of cases, it is possible during repeated intervention to radically or partially remove the parasitic node from the liver.

Mechanical jaundice in a number of patients can be eliminated by various bile-draining interventions or stenting of ducts through parasitic tissue, which does not cure the patient, but alleviates his condition. Biliary-bronchial fistulas can be eliminated by resection of the lung area bearing the fistula and by affecting the parasitic node in the liver. In case of isolated metastases in the lungs or brain, it is possible to remove the lesion, provided that the main parasitic node in the liver is affected radically or palliatively.

Possible postoperative complications

Among postoperative complications, the most formidable is liver failure, which occurs after liver resections, especially extended ones. The risk of its development can be reduced by careful preoperative preparation, careful surgery with reliable hemostasis and active hepatoprotective and replacement therapy in the postoperative period.

Mortality after liver resection for alveolar echinococcosis is 5%.

Further management

After radical liver resection, a patient with alveococcosis is unable to work for 2-3 months, and then can return to work. After palliative liver resections, patients remain healthy for 10 years or more if the intervention was performed using cryotechnics. After palliative interventions, the patient is transferred to disability.

All patients operated on for alveococcosis require dispensary observation with ultrasound monitoring once every 6 months to detect possible relapse or progression of the process after palliative interventions. It is recommended to conduct courses of treatment with albendazole.

How to prevent alveolar echinococcosis?

Prevention of the disease consists of observing personal hygiene rules, especially when slaughtering caged animals, dressing skins and picking berries. Fur farm workers must carefully observe personal hygiene rules and have protection (mittens, armlets and aprons) when caring for animals and especially when slaughtering them.

Complete prevention of alveococcosis is very difficult due to the fact that the development cycle of the parasite is mainly limited to wild animals, the impact of humans on which is minimal, and dogs are rarely the final hosts of alveococcus.