Echinococcosis. Echinococcus.- Causes, symptoms and treatment. MF.
This parasitosis is ubiquitous in the world, more often it is the southern regions of countries or countries with developed livestock. In Russia, the incidence of echinococcosis ranges from 1 to 4 cases per 100 thousand of the population. The main problem of echinococcosis is late diagnosis due to low-intensity symptoms of the disease at an early stage.
Echinococcosis is a chronic parasitic disease affecting animals and humans caused by Echinococcus granulosis chain( echinococcus), characterized by the defeat of internal organs, more often of the liver and lungs, with the formation of echinococcal cysts and the development of serious disorders of the functions of the affected organs.
Echinococci
Geographic spread of echinococcosis is extensive. The disease covers many southern countries of the world, as well as northern livestock areas of countries. Some of them include southern European countries, such as Bulgaria, Greece, Spain, Italy, Cyprus, many countries of South America, for example, Brazil, Argentina and others, Australia, India, Japan, southern USA.In Russia, echinococcosis occurs with a certain frequency in the Stavropol Territory, the Krasnodar Territory, Tatarstan, Bashkortostan, northern livestock areas of the Khabarovsk Territory, the Krasnoyarsk Territory, the Altai Territory, Tomsk and Omsk regions and others.
Causes of development of echinococcosis
Causative agent of echinococcosis
The disease is caused by the larval stage of Echinococcus granulosis. This is the smallest tapeworm, 2.5-8 mm long( sometimes 9 mm), has a scolex( head) with 4 suckers and hooks( the hooks form two rows with a total of up to 50).Sexually mature worm has a head, neck and 3-4 segments, which differ in the degree of maturity: first go unripe segments - 1-2 pieces, then the hermaphrodite, and the terminal mature segment. It is the mature segment that contains the uterus with eggs( from 400 to 600 pieces).Each egg contains an oncosphere( a 6-ticle larva-fetus).Onkosfery fairly stable in the external environment: withstand extreme temperatures from minus 30 ° to plus 35-40 °, in the surface layer of the soil remain up to several months at a temperature of 12 to 25 °, but the sunlight destroys the oncosphere for several days.
Echinococcus and oncospheres
Sources of infection
Ultimate host - dogs, wolves, foxes, jackals, coyotes, lynxes, lions.
Intermediate host - sheep, buffaloes, horses, pigs, squirrels, rabbits, humans. Possible transmission through the placenta - from the mother to the fetus in the case of the primary development of infection.
Scheme of circulation of parasitic invasion: Ultimate host( animal) - the environment( where feces are excreted with oncospheres and joints) - an intermediate host( in particular, a person) or an uncontaminated final host. Man, as an intermediate host, is a biological dead end( that is, does not allocate eggs and segments of the helminth to the environment, hence, is not a source of infestation).
Echinococcosis, development cycle
Mechanisms of infection with echinococcosis
The main mechanism of human infection is alimentary, contact-household. Human infection occurs when contact with the wool of animals - the owners of helminths( often dogs), when collecting berries and herbs, drinking water from contaminated sources, eating vegetables and fruits contaminated with feces of the final host( eg dogs).
Susceptibility is universal, however, individuals of certain occupations or lifestyles related to livestock( workers of slaughterhouses, shepherds, tanners, hunters and others) are at high risk.
A short cycle of development of echinococcus in animals: In the final host( dogs, wolves and others) - the embryo enters the body when eating the internal organs of the intermediate host( rabbits, squirrels, pigs and others) infected with echinococcus. On the mucosa of the small intestine develops a sexually mature individual, producing eggs. Segments with ripened eggs come off the body and come out with feces. They have mobility. Eggs are stored in the external environment for a long time depending on the conditions. Parasitize adults about 5-6 months, sometimes up to 12 months.
A short cycle of development of human echinococcus: Through the mouth, eggs enter the intestine of the intermediate host( for example, a human) where an embryo leaves the oncosphere, which is absorbed into the blood and enters the liver and sometimes into the lungs through the portal vein system. Here there is a stage of larval development in the form of a single-chambered bubble( larvocysts) with a diameter of up to 5 cm. The wall of the bladder consists of external chitinous and internal embryonic membranes. The cavity is filled with liquid. Inside the maternal bladder, daughter and grandchildren can form. The total weight of the bubbles can reach several tens of kg and 6-10 liters of liquid. On the inner shell of the bladder, brood capsules are formed to develop the inverted scolex. Scolex can separate from the capsules and freely swim in the fluid cysts. The main effect is associated with the formation of specific echinococcal cysts in any organ, but most often it is the liver( up to 80%) and the lungs( up to 20%).It can be either one cyst or multiple echinococcosis.
Echinococcal cysts
Echinococci exert:
1) sensitizing action( development of an allergic reaction of immediate or delayed type, and with rupture of cysts up to anaphylactic shock);
2) mechanical action - echinococcal cyst, expanding, leads to a significant disruption of the function of the affected organ, and subsequently the organ atrophy. The outcome may be fibrosis, in the lungs - pneumosclerosis. The timing of the formation of cysts varies depending on the number of oncospheres and the initial state of the human body. On average, from the moment of invasion( ingestion of oncospheres) to the formation of a bubbly structure of the larvae, it takes about 2 weeks, after a few months( 4.5-5 months), the cyst has a diameter of up to 5 mm, and then grows with years. Large cysts up to several liters in volume are formed over decades( 20 years or more).
Immunity with echinococcosis is unstable, repeated infections are possible.
Clinical forms and symptoms of echinococcosis
Several stages are distinguished during helminthiasis:
1) asymptomatic( from the moment of invasion to the formation of a small initial cyst);
2) the emergence of small complaints and symptoms of damage to an organ;
3) severe symptoms of the disease;
4) development of complications of invasion.
This gradation is very conditional because of the slow development of the disease, the slow growth of cysts.
Echinococcosis of the liver( more often)
Patients are troubled by weakness, nausea, decreased appetite, vomiting, stool disorder, itching rash, abdominal pain( right hypochondrium, epigastrium).When examined, there is an increase in the size of the liver and spleen( hepatosplenomegaly).The cyst can be accessible by palpation, dense to the touch. If secondary bacterial flora is attached, the cyst is inflamed, and clinically the patient will have fever( fever), chills, abdominal pain. An abscess of the liver can develop. When squeezing the cyst of intra- or extrahepatic bile ducts, jaundice of mechanical( or obturation) nature may develop. First, the urine darkens, the sclera turns yellow, the stool begins to lighten, then the skin becomes yellow. Jaundice is intense, often accompanied by pruritus. In the general analysis of blood - an increase in leukocytes, eosinophilia( up to 15-25%).
A severe complication of liver echinococcosis is the perforation of the echinococcal cyst, which is clinically manifested by severe pain, severe allergic reactions, up to anaphylactic shock, and dissemination of echinococci throughout the body will occur with the development of secondary multiple echinococcosis.
Echinococcosis of the liver
Echinococcosis of the lungs
With large cysts, patients suffer from shortness of breath, chest pain, hemoptysis. There may be a deformation of the chest, a shortening of the percussion sound and a weakening of the breath. There may be a displacement of the mediastinum. The pleura may develop into the process with the development of exudative pleurisy( inflammation of the pleura, exudation of the fluid).
When the cyst breaks, the symptoms change. If a breakthrough in the bronchi, the patient appears a sharp cough, choking, cyanosis, severe allergic reactions. The breakthrough of the cyst into the pleural cavity and pericardium leads to the development of anaphylactic shock with a fatal outcome.
In UAC: leukocytosis with a stab-shift( increased ratio of stab neutrophils to segmented neutrophils), eosinophilia( up to 15-25%).
Very rarely, but with echinococcosis, other organs can be affected: spleen, kidneys, CNS .This
occurs when the larvae migrate to a large circle of blood circulation. One of the important signs - repeated allergic reactions in the form of urticaria against the background of the emerging symptoms of the defeat of a particular organ.
Echinococcosis of the right lung
Diagnosis of echinococcosis
For the diagnosis of invasion, a properly collected epidemiological history is important( patient's connection with livestock, frequent visits to forests, meadows, close contact with animals-dogs and others).
Laboratory and instrumental diagnostics includes:
1) Ultrasound examination of the abdominal cavity organs, CT, R-graph of the lungs for the purpose of detecting single or multi-chamber cysts. If a cyst is found, puncture examination is unacceptable to avoid fatal outcomes for patients.
Echinococcosis of the liver on ultrasound
2) Serological examination of the blood of the patient for the purpose of detecting specific antibodies( using the reactions: RNIF, RNGA, ELISA) with high specificity of the methods from 80 to 90%, and high sensitivity up to 98%.The overwhelming majority of patients with cysts detected and suspected of their echinococcal nature have specific antibodies to the echinococcus in the blood.
3) Helminthological studies of ( sputum, duodenal contents, urine) in case of cyst break through into the lumen of the hollow organs in order to detect schelexes of echinococci.
4) The general clinical method of is a general blood test( leukocytosis, eosinophilia), biochemical studies( elevation of ALT, AST, GGTP, bilirubin by direct fraction) and others.
Treatment of echinococcosis
The main method of therapy:
1) surgical treatment( removal of echinococcal cysts followed by restoration of the function of the affected organ).The method of radical echinococcectomy( complete removal of the cyst with fibrous membrane) or opening of the cyst, removal of fluid, complete cavity treatment with special disinfectants, drainage, sewing tightly. Any opening of the echinococcal cyst should be carried out with the utmost care to avoid re-seeding( tissue isolation, prevention of ingress into the cavity - thoracic or abdominal).
2) If the operation is not possible due to a massive lesion, antiparasitic treatment is performed. Albendazole is administered with a course of 3 weeks or several months, the number of such cycles up to 20 times. The intervals between them are 21-28 days. Efficiency ranges from 41 to 72%( on average, 25% of patients recur).An alternative medicine is mebendazole for 15-24 months. Antiparasitic treatment is also performed in the postoperative period to prevent dissemination, in patients in endemic foci with the presence of antibodies to echinococcus, but the absence of cysts with a full instrumental examination.
3) Symptomatic therapy( antihistamines, hepatoprotectors, antitussives and
others depending on the symptoms).
Prevention of echinococcosis
1) Special veterinary measures to prevent the invasion of animals( dehelminthization of dogs, compliance with sanitary regulations in slaughterhouses).
2) Examination of decreed persons for echinococcosis( hunters, cattle breeders, dog breeders, slaughterhouse workers, meat packing plants and others)
3) Individual prevention: limiting contact with dogs, observing personal hygiene rules - washing hands, careful processing of vegetables, fruits, berries before meals, drinking water from trusted sources.
Physician infektsionist Bykova N.I.