What is Opisthorchiasis?

Opisthorchiasis – helminthiasis that affects the bile ducts of the liver, gallbladder and pancreatic ducts. Differs in a long course, proceeds with frequent exacerbations and contributes to the occurrence of cancer of the liver and pancreas. In 1884, S. Rivolta in northern Italy found a helminth in a cat, previously unknown to science, and called it a cat fluke. It took only 7 years, and this helminth was found in humans in Siberia. In 1891, Professor K. N. Vinogradov, during an autopsy of the human liver, discovered a small helminth, described it and called it Siberian fluke. Subsequent studies showed that the cat fluke and the Siberian fluke are one and the same kind of helminth. Considering the name “fluke” is wrong, because the helminth has one mouth, it was attributed to the genus opistorchis — that is, zadnemenkovy (testes are located behind), and the disease was called opisthorchosis. Opisthorchiasis – natural focal zooanthroponosis. Distributed in the form of foci of varying intensity. The formation of foci is determined by many factors: natural and climatic – the presence of reservoirs suitable for dwelling intermediate hosts; general sanitary – determining the possibility of contamination of water bodies with sewage, as well as the eating habits of people who use raw salted fish. The causative agent of opisthorchiasis is found in cats, dogs, foxes and other animals, as well as in mollusks and fish of the family karow in many European countries: Austria, Albania, Bulgarians of Hungary, Germany, Greece, Holland, Spain, Italy, Poland, Romania, Turkey, Finland, France. However, the vast majority of the modern world range of opisthorchiasis is concentrated on the territory of Russia and Ukraine, in three main foci – Ob-Irtysh, Volga-Kamsky and Dneprovsky. The territory in Russia that is endemic for opisthorchosis is Western Siberia and Kazakhstan in the Ob, Irtysh, Tobol and their tributaries, as well as in the Volga, Kama and their tributaries, in the Neman, the Northern Dvina, Pripyat, and the Don basin. Opisthorchiasis is widely spread in Ukraine. It represents a serious socio-economic problem for the regions located in the basin of the Dnieper and its tributaries (Psel, Sula, Seim, Vorskla, etc.), Sumy, Poltava, Chernihiv, less than Dnipropetrovsk, Kherson, Kiev regions. In the Dnieper basin, the level of endemia is generally lower than in Siberia, especially on the Ob. However, there are also villages with a high prevalence of residents, for example, Dobrianskoe and Ruchki villages in the Sumy region, where the invasiveness of the population reaches 30–60%. Despite the fact that over the past decade, the level of invasion of the population has significantly decreased, the dynamic system of this indicator indicates the need for mandatory surveillance. Data from past years indicate that opisthorchosis is infected with carnivorous animals (mostly cats) in the Dnieper basin and its tributaries (up to 32%), the Southern Bug (up to 28%), the Seversky Donets (up to 25%), the Dniester (up to 19%). The invasion of mollusks by the cercariae of the opisthorch varies from 0.3 to 1.5% in the basins of these rivers, and from the carp family of metacercariae, from 3 to 18%.

Causes of Opisthorchiasis

The causative agents of opisthorchiasis are two types of trematodes – Opisthorchis felineus and O. viverrini (Poiries, 1886, Hassal, 1896), which are similar in their systematic position, development cycle, morphology, pathogenesis, and clinic of the disease caused. The main causative agent of human opisthorchiasis is Opisthorchis felineus (Rivolta, 1884). Opisthorchiasis vivera is common in Southeast Asia (Thailand, Laos, India, China). Opistorhis – a relatively small flute. The shape of the body is leaf-shaped, lanceolate with a pointed front end, length 8-18 mm, width 1.2-2 mm. It has oral and abdominal suckers. From the mouth of the sucker go throat, esophagus, from which the double intestine departs. In the back end, place the excretory (excretory) channel. The reproductive system is hermaphroditic. Male organs are represented by two lobe testes, seminal receptacle – in the posterior third of the body; females – with uterus and zheltochnik, pushed forward and occupying the middle part of the body. The genital opening opens in front of the abdominal sucker. Per day one individual produces up to 900 eggs. The eggs are small, pale yellow in color and resemble a cucumber seed. On one pole of the egg is a cap, on the opposite side there is a tubercle, sizes – 26 – 30 x 10 – 15 microns. Life cycle. Opistorchis – biohelminths. In the life cycle, ensuring their circulation in nature, the final and two intermediate hosts are involved. The final owners are man and 34 species and one subspecies of mammals, representatives of 7 groups of 15 families: cat, dog, pig, fox, arctic fox, sable, wolverine, beaver, otter, ferret, hamster, raccoon, ermine, mink, weasel, columns, a badger, a chipmunk, a hare, a shrew, a wolf, a brown bear, a lion, a seal, etc. In the laboratory, they infect rats, mice, rabbits, guinea pigs, monkeys. The first intermediate host is a freshwater mollusk (Vogel, 1932) of the genus Bithynia inflata, by the modern definition of Cadiella (Mefodiev, 1988). It is a molluscian mollusk, the inhabitant of shallow, well-warmed, vegetation-rich water bodies with stagnant water or its weak current, especially floodplain water bodies, drying up old ladies, with a maximum depth of 2 to 3 meters. Cadiella biotopes occur when the pH of the water is not more than 7.5, when the chlorine content is not more than 50 mg/l. Bithonias migrate when the ground dries, for a month they are able to move by 4 m, stay in suspended animation for 7–10 months a year. They tolerate low temperatures well, winter in freezing ground. The time of awakening of the mollusk depends on the water temperature not lower than 10 – 20 ° С. Sexual maturity occurs in the second year of life (S. A. Beer). The second intermediate host (or additional) —fishes of the carp family (proved by Brown in 1893): ide, tench, roach, dace, chub, guster, bream, rudd, podust, sabrefish, slope, bluefinch, white-eyed, verkhovka, shipipov and etc. In the final host, opisthorchias are parasitic in the liver ducts (100%), the gallbladder (43–60%), and in the pancreatic ducts (32–36%). Mature individuals secrete eggs, which, with the feces of the invasive one, go outside and enter the water, to the bottom of the reservoir. Miracidia develops in the egg. The mollusk swallows the egg; in its body, the miracidium turns into a sporocyst. In the sporocyste, several dozen redia are formed from the embryonic mass, in which up to 100-120 cercariae are further formed. Having reached maturity, the cercariae emerge into the water, actively moving, displaying positive geo-and phototaxis. As a result, swimming in the lower layers of water, they attack a fish passing by, the shadow of which, during its movement, activates the tailed larva. Once on the skin of the fish, the cercaria strengthens, sticks to it, losing its tail, and penetrates into its thickness. The penetration of cercariae into the body of the fish through the natural openings of the lateral line or when swallowed with mature cercariae is not excluded. In subcutaneous tissue and muscle tissue of infected fish, metacercariae are formed — incisive rounded or oval-shaped larvae (0.24-0.34×0.18-0.24 mm), localized in the dorsal external muscles. After 6 weeks, metacercariae become invasive for the final hosts. Their further development occurs in the organism of the final host, which, eating eating fish infected by metacercariae, becomes infected with opisthorchosis. In the duodenum under the action of gastric juice and digestive enzymes tissue fish digested and metacercaria, freed from the shell, along the common bile duct penetrate the liver and gall bladder, along the Wirsung duct into the pancreatic ducts. The promotion of metacercaries is fast (3-5 hours), and after 1.5-2 weeks they reach puberty. The duration of parasitic opisthorch in humans is years – 10-20-30 years.

Pathogenesis during Opisthorchiasis

In the course of opisthorchiasis, there are two stages of the disease, which is caused by the peculiarities of the development of the pathogen. Once in the human body in the larval stage, the causative agent undergoes a phase of maturation in it to a mature individual, and then for many years inhabiting the intrahepatic and extrahepatic bile ducts, the gall bladder and the pancreas. In the early stage of the disease, the leading pathogenetic factor is the development of a common allergic reaction in response to exposure to metabolic products, enzymes of a growing parasite. It is based on the development of proliferative processes in the lymph nodes, spleen, proliferative-exudative reactions in the skin, mucous membranes of the respiratory tract, and digestive organs. An important role is played by the disorder of microcirculation and hypoxia with impaired gas exchange, especially in the blood of the liver. As a result of these effects – the development of dystrophic processes in the liver, myocardium and other organs. The development of organ pathology depends on the intensity of infection, as well as on the availability of immunological tolerance among the indigenous people of the lesions, in which the acute phase passes more easily than in the “non-immune” ones – visitors to the lesion. The pathogenesis of the chronic stage of opisthorchiasis is based on all the pathology’s multifactorial nature: the mechanical, allergic, neuro-reflex influence of adult worms, the secondary influence of the microbial flora, and the body’s autosensitization with the products of the death of its own tissues — epithelial cells of the bile ducts and the gall bladder. The phenomena of chronic proliferative cholangitis, pericholangitis develop, structural changes in the form of chronic hepatitis occur in the liver parenchyma, and in the long run – cirrhosis of the liver. Neuro-reflex influence caused by mechanical and toxic irritation of the vagus and sympathetic nerves, as well as duct interoreceptors, leads to dyskinesia of the biliary tract and gall bladder, disorders of the secretory and motor functions of the stomach, motility of the duodenum. Violated the functional state of the pancreas and adrenal cortex. As a result of chronic inflammatory changes in the mucous membrane of the stomach and duodenum of an allergic nature and hormonal disorders, invasion, as a rule, accompanies chronic gastroduodenitis. Opisthorchiasis is a factor predisposing to the development of primary liver cancer – cholangiocarcinoma. The source of invasion for opisthorchiasis is the final owner – people and pets (cats, dogs, pigs, etc.). Do not underestimate the role of wild animals (wolf, fox, wild boar, muskrat, water vole, etc.) in the preservation and maintenance of natural foci, and hence the causative agent of opisthorchiasis. With the feces of the final host, opisthorch eggs enter the reservoir in different ways: when wastewater is discharged, sewage is washed away by rain and melt water from the banks, etc. The maximum duration of preservation of opisthorch eggs in Siberia is 29 months. The formation of the center of opisthorchiasis depends on the possibilities and conditions of infection of the intermediate and additional hosts. The infection of the intermediate host – the mollusk – is caused by a number of factors: the size and density of their populations depending on the temperature and flow rate of the water, salt content, susceptibility to the pathogen, etc. The life expectancy of free swimming cercariae O.felineus does not exceed two days. Infection of carp fish depends on the number of mollusks, the emission of cercariae, the hydrological features of the reservoir. Opisthorchosis is infected by people of any age, but more often at the age of 20-40 years old, especially fishermen, members of their families, workers’ fishing cooperatives, fish-processing enterprises, seafarers, backeders, that is, people professionally involved in catching or processing fish. They constitute a risk group. Infection occurs by eating poorly cooked, roasted, slightly salted, dried, raw fish. Metazerkarii are distinguished by high viability: at a temperature of -3-12 ° C, they persist for up to 25 days, at – 30-40 ° C – 5-6 hours. They are less resistant to high temperatures and strong salting. In the northern foci of Russia, the use of stanutine contributes to the infection, while in the foci of opisthorchiasis in Ukraine – salted, dried fish.

Symptoms of Opisthorchiasis

Acute phase. The disease begins 5–42 days after infection. The average incubation period is 21 days. An acute onset of the disease prevails, less often – a gradual onset with the manifestation of indisposition, weakness, sweating, low-grade fever. In the future, opisthorchiasis can occur subclinical, asymptomatic, accompanied by a short-term rise in temperature to 38 ° C, eosinophilia up to 15-20% against the background of moderate leukocytosis. Acute opisthorchosis of moderate severity (40–50% of patients) is characterized by high fever with a gradual increase in temperature to 39–39.5 ° C, catarrhal phenomena of the upper respiratory tract. Eosinophilia reaches 25–60%, leukocytosis increases, ESR increases moderately to 20–40 mm/hour. In patients with mild to moderate severity, after 1 to 2 weeks, improvement occurs, the latent period of the disease, which later becomes chronic. In severe acute opisthorchiasis (10–20% of patients), there are typhoid, hepatocholangitic, gastroenterocolitic variants and a variant with a primary lesion of the respiratory tract in the form of asthmoid bronchitis, pneumonia. For the typhoid variant, which most clearly reflects the allergic nature of the acute phase, is characterized by acute onset, high fever with chills, lymphadenopathy, skin rashes. Cardialgia is often noted with diffuse changes in the myocardium on the ECG, intoxication phenomena. From the first days of the illness, severe weakness, severe headaches, myalgias and arthralgias, dyspeptic manifestations, coughing and other allergy symptoms are observed. Eosinophilia reaches 80 – 90% with leukocytosis up to 20-30-109 / l, increased ESR up to 30-40 mm/hour. The acute phenomena proceed 2-2,5 weeks. Hepato cholangitis occurs with high fever, eosinophilia and symptoms of diffuse liver damage: jaundice, hepatosplenomegaly, functional impairment – an increase in serum bilirubin in the direct reaction, an increase in protein level due to a2 – y globulins, changes in sediment samples (salivary, thymol) and etc). Symptoms of cholangiohepatitis include abdominal pain syndrome: dull pain, aching, pressing, sometimes the type of hepatic colic. In more severe cases, the symptoms of hepatobiliary disease are aggravated by manifestations of pancreatitis with dysfunction of the pancreas. Patients complain of the pain of shingles, in the right and left hypochondrium and dyspeptic manifestations. The gastroenterocolitic variant manifests itself clinically in the form of catarral, erosive gastritis, enterocolitis, gastric and duodenal ulcers. The most prominent symptoms of the disease are pain in the epigastrium, right upper quadrant, loss of appetite, nausea, less vomiting, impaired stool. When fibroscopy – erosive and hemorrhagic gastroduodenitis, sometimes ulcer niches. Fever and intoxication are less pronounced, eosinophilia up to 30 – 40%. In one third of patients, the respiratory organs are involved in the process in the form of inflammation of the upper respiratory tract, asthmoid bronchitis, pneumonia, pleurisy. As a rule, there is astheno-vegetative syndrome in the form of weakness, fatigue, irritability, sleep disorders. In some cases, there is a protracted course of the acute stage. Fever is delayed to two or more months, there are signs of liver damage, pulmonary syndrome. As the manifestations of the acute stage subside, the patient’s condition improves, the disease enters the chronic phase more often with manifestations of biliary dyskinesia, chronic cholangiohepatitis, chronic pancreatitis. Biliary dyskinesia and cholestasis contribute to the accession of a secondary bacterial infection. In these cases, the development of severe lesions of the hepatobiliary system of the type of cholangiohepatitis with severe pain, enlarged liver, jaundice, and impaired functional tests is possible. Most often it is persistent hepatitis with symptoms of “small liver failure” and astheno-vegetative syndrome. In cases of accession of the lesion of the pancreas, symptoms of pancreatitis are detected. Among the forms of lesions of the gastrointestinal tract, chronic gastritis is more often registered, in which, depending on the degree of damage to the glandular apparatus, violations of the secretory, acid-forming, pepsi-forming and protein-secreting functions are detected. Along with gastritis, duodenitis often develops with a corresponding set of symptoms. Frequent complaints of patients to pain in the heart, pulse interruptions, which are associated with dystrophic changes in the myocardium (ECG). The phenomena of astenisation of the organism prevail due to inhibition and even depletion of the pituitary gland – the adrenal system. In severe cases, the prognosis becomes serious. Complications of opisthorchiasis include cirrhosis of the liver, biliary peritonitis, and primary cancer of the liver and pancreas. Signs of lesions in opisthorchiasis of the nervous system are indicated by complaints of headache, dizziness, irritability, insomnia, depression, etc. In the chronic phase of opisthorchiasis also marked eosinophilia, but a lower level, leukopenia, moderate hypochromic anemia. Opisthorchiasis aggravates the course of associated diseases, adversely affects the course of pregnancy, the lactation period, and also contributes to the formation of typhoid-paratyphoid carriage. Superinvaziya (re-infection of a patient with opisthorchiasis) causes a progressive course of the disease. Local residents of opisthorchiasis have a subclinical course of invasion with moderate manifestations of the asthenovegetative or dyspeptic syndrome, cases of the acute phase are rarely recorded. The most common form of manifestation of opisthorchiasis is cholangiohepatitis. The course of opisthorchiasis in children is characterized by the fact that the acute phase is recorded much less frequently and proceeds in a mild form. Chronic phase in children 1–3 years of age is manifested by a lag in physical development, symptoms of biliary dyskinesia, moderate eosinophilia, and reduced nutrition. As they grow older, sensitization effects increase, and in adolescence, organ pathology characteristic of adults is determined. Complications of opisthorchiasis: purulent cholangitis (inflammation of the biliary tract), rupture of cystic dilated bile ducts with the subsequent development of biliary peritonitis, acute pancreatitis (inflammation of the pancreas), liver cancer.

Diagnosis of Opisthorchiasis

Diagnosis of opisthorchiasis in the early phase is difficult, because the eggs of parasites in the bile and feces are detected only after 4-6 weeks from the moment of infection. Therefore, the diagnosis of acute opisthorchiasis is based on data from the epidemiological history (stay in the outbreak, eating raw, dried, lightly salted fish there) and the clinical manifestations of acute allergic disease with fever, skin rashes, myalgia, arthralgia, catarral other phenomena with leukocytosis and leptocytosis. Given the high concentration of serum specific immunoglobulins predominantly of the JgM class, serological diagnostic methods can be used: RNGA – diagnostic titer 1: 256 reaches efficiency in 84.2% of cases; REMA – diagnostic titer of 1: 100, effective in 92% of patients. Reactions, unfortunately, can give false positive results with serum infested with fascioli, wild plants and other helminths. The diagnosis can be confirmed in 1–1.5 months based on the detection of opistorch eggs. To diagnose the chronic phase, a parasitological method is used, based on the detection of opistorchic eggs in duodenal contents or feces. In duodenal intubation, it is necessary to investigate all three portions (A, B, C), which is not always possible due to frequent biliary dyskinesia. The negative portion A has no diagnostic value, such probing requires repetition. For the purpose of “provocation” of ovary ejection, it is recommended that patients take 1.0 to 2.0 g of cloxyl before probing. The centrifuged sediment of bile is applied to the glass and carefully microscoped with a low magnification microscope. The most effective methods of coproooscopic diagnostics are the method of ether-formalin deposition of eggs, the method of ether-acetic sedimentation and thick smear according to Kato.

Treatment of Opisthorchiasis

Treatment of patients with opisthorchiasis, both in the acute and in the chronic phases, should be comprehensive with the principle of combining pathogenetic and etiotropic therapy. Staging in the treatment regimen includes: preparation, prescription of an anthelmintic drug against the background of pathogenetic therapy, rehabilitation, clinical examination, control of the effectiveness of treatment. Treatment of patients in the acute phase is primarily aimed at stopping allergic reactions and related organ pathology. For this purpose, prescribe antihistamines (diphenhydramine, suprastin, tavegil), calcium chloride, sedatives (preparations of valerian, bromine). As anti-inflammatory drugs, taking into account the development of vasculitis, salicylates, butadione, askorutin are prescribed. Exemption from invasion does not ensure complete restoration of functional and organic disorders of the hepatobiliary system, the gastrointestinal tract, the immune system and microcirculation. In this regard, patients need rehabilitation treatment, individualized with regard to the remaining pathology. As a rule, the rehabilitation complex includes a general strengthening treatment, preparations that improve the functional state of the biliary system, anti-inflammatory therapy, physiotherapy, good dietary nutrition, etc. During the first two months after discharge from the hospital, it is advisable to carry out duodenal sounding, tyubazhi with sorbitol, 25 – 33 % sulphate of magnesia once a week. Clinical examination provides for staged observation of a patient with opisthorchiasis in the hospitals and clinics of KIZov. The timing of follow-up is determined by the severity of the pathology and, taking into account clinical indications, is carried out for 2–3 years or more. Clinical and laboratory examinations should be carried out at least once every six months. Considering the possibility of re-infection (superinvasion, reinvasion), educational and sanitary work among patients is important. The doctor in conversations with patients explains the measures of infection prevention, the rules of cooking fish.

Prevention of Opisthorchiasis

Methods of control and prevention include a multi-faceted set of measures: treatment-and-prophylactic: – identification of invasive ones; – deworming infested; – control, examination of the treated; dispensary observation; sanitary and epidemiological: – protection of water bodies from fecal contamination; – control over the observance of fish processing technology (salting, smoking, drying, etc.). The measures for the control of mollusks (fenasal, its salts) tested in the conditions of the West Siberian focus in the outbreaks of Ukraine have not been tested and are hardly expedient. Full radical implementation of these activities provides community prevention. sanitary and educational work, especially in areas unfavorable for opisthorchiasis, is carried out in conjunction with therapeutic measures. Methods of health education are varied: memos, individual conversations, speeches in the press, radio, on television. Special attention should be paid to risk groups, visiting workers, employees, showing opisthorch preparations, tables, giving examples of case histories. It is necessary to explain to the population the rules for processing fish at home: – Boil fish (fish soup) for at least 20 minutes. from the beginning of the boil, fry – in the form of a plastovanny 15-20 minutes. – Hot smoking after salting neutralizes fish. – Fish salting should be carried out at a temperature of +16 – + 20°С for 14 days with salt consumption of at least 14% of its mass. – Freezing in ice-salt mixture is not recommended, since the metacercaries remain in fish alive for 2 to 4 weeks. – In fish canned food and hot smoked fish, viable metacercariae is not found.

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