Echinococcosis is a parasitic invasion by the larval stage of the echinococcus tapeworm, occurring with damage to internal organs (liver, lungs, heart, brain, etc.) and the formation of echinococcal cysts in them. Nonspecific symptoms of echinococcosis include weakness, urticaria, transient fever; specific ones depend on the location of the parasite and can be represented by local pain, nausea, jaundice, cough, focal neurological symptoms, cardialgia, arrhythmia, etc. Diagnosis is based on data from instrumental studies (X-ray, scintigraphy, ultrasound, CT) and serological tests. Treatment is surgical.
Echinococcosis is a helminthic disease from the group of cestodoses caused by the parasitization of echinococcus in the human body at the stage of the oncosphere. In the world, the highest incidence of echinococcosis is observed in Australia, New Zealand, North Africa, South America, Southern Europe, and Central Asia.
In endemic regions, the incidence of echinococcosis reaches 5-10%. The prevalence of echinococcosis is closely related to the development of animal husbandry. Given the fact that various internal organs can be affected with echinococcosis, and the only radical method of treatment is surgery, the disease lies in the sphere of interests of thoracoabdominal surgery, neurosurgery, cardiac surgery.
Human echinococcosis is caused by the larval stage of the tapeworm Echinococcus granulosus – lavrocyst. The final hosts of mature helminths are animals (dogs, foxes, wolves, lions, lynxes, etc.), in whose intestines cestodes parasitize. Humans, domestic and wild herbivores (cattle, pigs, horses, deer, moose, etc.) are intermediate hosts of larval stages and at the same time a biological dead end, since they do not secrete echinococcus eggs into the environment and cannot serve as a source of invasion.
Adults of echinococcus are small helminths 2.5–8 mm long and 0.5-10 mm wide, having a head with four suckers and two rows of hooks, a neck and several segments. Mature segments contain echinococcus eggs with oncospheres and a six-pronged larva-embryo inside. Oncospheres survive in a large temperature range (from -30 ° C to +30 ° C), remain in the soil for several months, but soon die under the influence of sunlight.
From the intestines of the final host, eggs with feces are released into the external environment. Infection of people with echinococcosis occurs alimentary (when eating vegetables and fruits contaminated with feces, water) or by contact (when cutting carcasses or contact with animals infected with echinococcus). Persons engaged in animal husbandry and animal care (animal breeders, hunters, slaughterhouse workers, etc.) have a high risk of echinococcosis.
In the human gastrointestinal tract, under the action of digestive enzymes, the shell of the egg and the oncosphere dissolves, and the larva comes out. With the help of hooks, it is introduced into the intestinal mucosa, from where it enters the venous bloodstream and the portal system. Most of the oncospheres settle in the liver; sometimes, through the inferior vena cava, oncospheres enter the right parts of the heart, and from there – into the small circulatory circle and lungs. Less often, through the pulmonary veins and the left parts of the heart, the embryos are in a large circle of blood circulation and can be brought into any organ: the brain, spleen, kidneys, muscles, etc. As a result of invasion, liver echinococcosis develops in about 70-80% of cases, lung echinococcosis develops in 15%, and in other cases, other organs are affected.
After the echinococcal embryo settles in one or another organ, the vesicular or hydatidous stage of parasite development begins. The echinococcal vesicle is a cyst covered with a two-layer shell consisting of an inner (germinal) and outer (chitinous) layers. The cyst slowly increases in size (by about 1 mm per month), but after years it can reach gigantic sizes. Inside the echinococcal bladder contains a transparent or whitish opalescent liquid in which daughter bubbles and scolexes float. Daughter bubbles of echinococcus can also form outside the chitin shell; their total number can reach 1000.
Manifestations of echinococcosis are associated with the sensitizing effect of parasitic antigens and the mechanical pressure of the cyst on organs and tissues. The parasitization of echinococcus is accompanied by the release of metabolic products, which leads to the development of intoxication and a delayed allergic reaction. In the case of a complete rupture of the cyst, its contents flow into the pleural or abdominal cavity, which can cause anaphylactic shock. The increasing size of the echinococcal cyst presses on the surrounding structures, disrupting the functions of the affected organ. In some cases, suppuration of the cyst develops; less often, spontaneous death of echinococcus and recovery are possible.
Echinococcosis can be asymptomatic for years and decades; in the case of clinical symptoms, there are no pathognomonic signs. Regardless of the localization of the parasite in the body, echinococcosis passes through three stages in its development:
- I – asymptomatic. The course of the latent period begins from the moment of the introduction of the oncosphere into the tissues and continues until the first clinical signs of echinococcosis appear.
- II – stage of clinical manifestations. During stage II, patients are concerned about pain at the site of cyst localization, weakness, urticaria, itching, as well as specific symptoms caused by parasitization of the cystic form of echinococcus in a particular organ.
- III – stage of complications. In the stage of complicated echinococcosis, a cyst rupture may occur and the contents flow into the abdominal or pleural cavity with the development of peritonitis, pleurisy. With suppuration of an echinococcal cyst, high fever and severe intoxication are added. Cyst compression of organs and tissues can cause the development of mechanical jaundice, ascites, dislocations, pathological fractures.
Echinococcosis of the liver
Echinococcosis of the liver is characterized by complaints of nausea, decreased appetite, recurrent diarrhea, heaviness and pain in the right hypochondrium. Objectively, hepatosplenomegaly is detected; sometimes an echinococcal cyst of the liver is palpated in the form of a rounded dense formation. In the case of compression of the bile ducts by a cyst, mechanical jaundice develops; with compression of the portal vein, ascites, portal hypertension occurs. The addition of secondary bacterial flora can lead to the formation of a liver abscess. The most severe complication of liver echinococcosis is cyst perforation with the development of acute abdominal pain, peritonitis and severe allergic reactions. In this case, the dissemination of echinococci occurs, as a result of which secondary echinococcosis with multiple localization develops.
Echinococcosis of the lungs
Echinococcosis of the lungs occurs with an increase in body temperature, intoxication syndrome, chest pain, cough, hemoptysis. The pressure of the cyst on the lung tissue leads to the formation of lung atelectasis. When the bladder breaks into the bronchi, a strong cough, cyanosis develops, often aspiration pneumonia. An extremely dangerous complication of pulmonary echinococcosis is a cyst breakthrough into the pleura and pericardium, which can lead to anaphylactic shock, a sharp displacement of the mediastinum, cardiac tamponade and sudden death. Infection of an echinococcal cyst is accompanied by the formation of a lung abscess.
Echinococcosis of the heart
With echinococcosis of the heart, chest pains that resemble angina are bothering. Compression by cysts of the coronary arteries can cause the development of myocardial infarction. Rhythm and conduction disorders often occur: ventricular tachycardia, incomplete and complete blockage of the legs of the Gis bundle, complete transverse heart block. The causes of death of a patient with echinococcosis of the heart can be malignant arrhythmias, heart failure, cardiac tamponade, cardiogenic shock, PE, postembolic pulmonary hypertension, etc.
Echinococcosis of the brain
The blade of echinococcosis of the brain is characterized by hypertension syndrome and focal neurological symptoms (impaired sensitivity, paresis of the extremities, epileptiform seizures).
The correct diagnosis of echinococcosis is facilitated by a detailed epidemiological history indicating close human contact with animals, endemic infection. If echinococcosis of any localization is suspected, serological blood tests (ELISA, RNIF, RNGA) are prescribed to detect specific antibodies to echinococcus. The specificity and sensitivity of the tests reaches 80-98%. In about 2/3 of cases, a skin-allergic test, the Kazoni reaction, turns out to be informative.
The range of instrumental diagnostics of echinococcosis includes ultrasound, X-ray, tomographic, radioisotope methods. The list of studies depends on the location of the lesion:
- With echinococcosis of the liver, ultrasound of the hepatobiliary system, angiography of the abdominal trunk (celiac), MRI of the liver, scintigraphy, diagnostic laparoscopy, etc. are informative.
- Lung echinococcosis can be recognized by lung radiography and chest CT, bronchoscopy, diagnostic thoracoscopy.
- CT or MRI are the leading methods of diagnosing echinococcosis of the brain.
- If a heart lesion is suspected, EchoCG, coronary angiography, ventriculography, and MRI of the heart are performed.
When an echinococcal cyst breaks through into the lumen of hollow organs, the parasite’s scolexes can be detected in the duodenal contents under study, sputum. Also in these cases, bronchography, cholecystography, puncture cholangiography are resorted to. Echinococcal cyst must be differentiated from alveococcosis, bacterial abscesses, cysts of non-parasitic etiology, liver, lung, brain tumors, etc.
Radical cure of echinococcosis is possible only surgically. The optimal way is to perform an echinococcectomy – peeling the cyst without violating the integrity of the chitin shell. In the presence of a large bladder, its intraoperative puncture with aspiration of the contents is performed first. The residual cavity is carefully treated with antiseptic solutions, tamponed, drained or sutured tightly. During the operation, it is important to prevent the contents of the bladder from entering the surrounding tissues in order to avoid dissemination of echinococcus.
If it is impossible to excise the cyst with echinococcosis of the lung, wedge-shaped resection, lobectomy, pneumonectomy is performed. A similar tactic is used for echinococcosis of the liver. If excision of an echinococcal cyst of the liver is technically impossible, marginal, segmental, lobar resection, hemihepatectomy is performed. In the pre- and postoperative period, antiparasitic therapy with praziquantel, albendazole, mebendazole is prescribed.
Prognosis and prevention
In the case of radical removal of echinococcal cysts and the absence of re-infection, the prognosis is favorable, there are no relapses of echinococcosis. In the case of intraoperative dissemination of scolexes, a relapse of the disease may occur after 1-2 years with the formation of multiple echinococcal blisters and an unfavorable prognosis.
Measures to prevent human invasion are veterinary control and animal health (periodic deworming of dogs, vaccination of sheep, improvement of hygienic conditions of livestock, etc.). Hunters, breeders, breeders of dogs should be informed about the danger of infection with echinococcosis, the need to comply with personal hygiene measures. Patients who have undergone echinococcosis are under dispensary supervision for 8-10 years with annual serological tests, ultrasound and X-ray examination.