Clonorchiasis is a chronically occurring helminthic invasion. The main symptoms are associated with the involvement of the liver and pancreas; with a significant duration of the disease, cirrhotic changes, acute pancreatitis may occur, and the likelihood of malignant neoplasms of the hepatobiliary system increases. Allergic reactions caused by the presence of a parasite in the body, lymphadenopathy are characteristic. Diagnosis of pathology is associated with the detection of the pathogen in the feces. Treatment – anthelmintic, desensitizing, anti-inflammatory and symptomatic therapy.
Clonorchiasis is trematodosis, that is, an infection caused by flukes. The first description of the helminth was made by the English researcher McConnell in 1874, later the pathogen was studied in detail by the Japanese scientist Kobayashi. The greatest prevalence of clonorchiasis is observed in Southeast Asia (most cases have been recorded in China, Korea and Japan). Today, due to labor migration, economic cooperation, and globalization, helminthiasis is becoming a problem of global infectology. Men over 35 years of age are more often infected, there is no clear seasonality.
The causative agent of helminthiasis is the fluke Clonorchis sinensis, Chinese fluke. The sources of infection are humans and mammals, the route of transmission is alimentary. Adult worms of C. sinensis usually live in the bile ducts of the final hosts, eggs are excreted with feces. Freshwater snails can serve as the first intermediate hosts. Eggs in water develop into miracidia, and after ingestion by snails – into sporocysts, redia and cercariae. Mature cercariae float freely in the water, invade the second intermediate hosts (freshwater fish) through the skin, and then form metacercariae in the musculature of the fish.
The main risk factors for clonorchiasis are work in catering establishments, fishing and farms, low organization of social and living conditions, small income of the population. The prevalence of fish with metacercariae in different regions varies from 7 to 102 freshwater species. One of the properties of helminth is a long-term (up to 40 years) persistence in the body without treatment, as well as a connection with the formation of fibrosis and malignant degeneration of hepatocytes, biliary duct tissue. The frequency of disability after nosology correlates with the severity of symptoms.
The mechanisms of the pathological effects of clonorchs have not been fully studied. Helminth causes periductal fibroplasia, starting from the 7th day of the disease, activates lipid peroxidation, which is accompanied by damage to the DNA of cells of the hepatobiliary apparatus. Hepatocytes undergo hydropic degeneration, abnormal cell apoptosis is suppressed, which promotes tumor growth. The maintenance of chronic inflammation leads to fibrous tissue changes, the formation of carcinomas.
Many patients with symptoms of this helminthiasis have a high level of IL-33/ST2, a powerful inducer of epithelial cell proliferation and fibrosis. The parasite-induced production of IL-13 and IL-10 avoids the effects of the immune system due to their pronounced anti-inflammatory effect; another effect of these interleukins is the induction of collagen formation in tissues. Excessive production of TNF-alpha and gamma interferons supporting chronic inflammation is noted in the cells of the bile-bubble epithelium.
The incubation period is long – from 2-4 weeks to decades. The onset of the disease has clinical manifestations only in 10-40% of patients, in other cases, symptoms are not detected or have little effect on the well-being of patients, which leads to the absence of etiotropic treatment. Helminthiasis can begin with the appearance of weakness, an increase in body temperature from 37.5 to more than 40 ° C, abdominal discomfort, loose stools, nausea, jaundice of the sclera. After 14-30 days, the symptoms disappear on their own or against the background of treatment, the patient feels healthy for a long time.
The manifestations of clonorchiasis are mainly associated with the defeat of the biliary system, the symptoms of dysfunction of which include aching pains in the right hypochondrium, heartburn, periodic nausea and bloating, flatulence, loose stools after fatty and fried food. Sometimes patients notice a dark color of urine (like strong tea leaves). With the development of cirrhosis, patients lose body weight, edema, sleep disorders, memory loss and other symptoms of liver failure appear. Most often, complications and severe course of clonorchiasis are registered in people 40-60 years old.
The most common are purulent complications associated with the addition of symptoms of bacterial inflammation of the walls of the gallbladder and intrahepatic ducts, abscesses. Less often there are chronic lesions of the digestive tract: peptic ulcer of the duodenum, duodenitis, pancreatitis, cholecystitis, hepatitis. Hepatic cirrhosis occurs in 0.06% of cases of clonorchiasis. The most common oncological pathology associated with prolonged invasion, lack of treatment for parasitosis is cholangiocarcinoma.
Confirmation of the diagnosis is carried out by an infectious disease specialist, a thorough collection of epidemiological anamnesis over the past decades is necessary. Other specialists – surgeons, gastroenterologists – are involved for consultation if there are indications. The main diagnostic laboratory and instrumental signs of infection are:
- Physical data. An objective examination in clonorchiasis often does not reveal pathological changes. In a number of situations, palpation of the abdomen reveals significant hepatomegaly, pain in the gallbladder, bloating, flatulence, less often splenomegaly, subictericity of the sclera. It is mandatory to study urine and feces (change in hue, smell, consistency of physiological secretions).
- Laboratory tests. The blood test determines leukocytosis, eosinophilia up to 80%, acceleration of ESR. There is an increase in the activity of hepatic transaminases, alkaline phosphatase, total and direct bilirubin, triglycerides; hypoalbuminemia. The urine analysis reveals a change in color, an increase in density, the appearance of biliary pigments, urobilinogen, single leukocytes.
- Identification of infectious agents. It is mandatory to conduct a coprooscopy using the Kato method or formalin-ether enrichment, taking into account the fact that the eggs of the clonorchus have similarities with the eggs of the opisthorchus and other flukes. Serological diagnostics is a highly sensitive method with a high probability of cross-reactions with antibodies to other flukes. The modern LAMP (isothermal loop amplification) technique is considered less expensive than PCR research.
- Instrumental methods. They are uninformative in the symptoms of clonorchiasis, but they help in carrying out a differential diagnosis with tumor processes, cholangitis of other origin. Ultrasound of the abdominal cavity is recommended, preferably with contrast, MRI. In some cases, a fine needle biopsy of liver tissue, diagnostic laparoscopy is performed.
Differential diagnosis is carried out with opisthorchiasis – clinically these pathologies are indistinguishable, laboratory confirmation is necessary. At the acute onset, the symptoms of clonorchiasis are similar to other helminthic lesions (ascariasis, trichinosis, toxocarosis), since the allergic component of the disease comes to the fore. Viral hepatitis often occurs with severe jaundice, a relatively short incubation period, and a characteristic anamnesis.
Hospitalization of patients with symptoms of chronic clonorchiasis is carried out according to clinical and epidemiological indications, with an acute course it is mandatory. With pronounced allergic, cholestatic symptoms, severe premorbid background, bed rest is prescribed. Dietary recommendations are associated with impaired function of the biliary system, liver tissue. Frequent fractional gentle nutrition is shown, fatty, fried, marinades, coffee, alcohol, carbonated drinks are excluded. It is desirable to increase the drinking regime in favor of boiled water, green tea varieties, unsweetened compotes, broth of rosehip.
The established diagnosis of clonorchosis allows you to start treatment after the preliminary stage, which consists in preparing the body for deworming within 10-14 days. It is necessary to observe a sparing diet, clarify the variant of bile duct dyskinesia (hyper-, hypokinetic) for adequate determination of ways to eliminate parasites, the use of pathogenetic agents. Then the patients receive etiotropic therapy, in the future it is necessary to restore the functions of the hepatobiliary system.
A single course of anthelmintic drugs lasting 7-21 days is effective in 90-94% of cases of infection, with a long (more than 10 years) existence of the parasite in the body, it is recommended to repeat the course treatment. Promising drugs, such as tribendimidine, have minimal side effects compared to praziquantel. The following types of treatment are used:
- Etiotropic therapy. Anthelmintic agents with proven activity against clonorhov are used – praziquantel and tribendimidine, prescribed by the course orally. Patients are informed about transient symptoms of dyspepsia, headaches and dizziness associated with the action of dosage forms and do not require medical correction. Hexachlorparaxylene is sometimes chosen as an alternative to the listed funds.
- Pathogenetic treatment. Choleretic drugs from the group of cholekinetics, antispasmodics (drotaverine), means of infusion detoxification – glucose-salt solutions, chlosol, succinate-containing medications are shown. Desensitizing agents such as calcium preparations are widely used, antihistamines and glucocorticosteroids are indicated for severe allergosis.
- Symptomatic therapy. It includes enzymes, enterosorbents, tubes with magnesium sulfate, borjomi, sorbitol 1-2 times a week. With symptoms of secondary flora attachment, a bacteriological study of bile and duodenal contents is carried out, antibiotics are added to the treatment regimen. Probiotics are recommended to restore the evacuation function of the intestine.
Modern researchers suggest using means with proven positive clinical effect on animals to eliminate the parasite. These include artemether, artesunate, OZ78 and mebendazole. The latter has shown good therapeutic results in co-infections with other helminthiasis. The effect of prednisolone on the activity of parasitic inflammation is being studied – in experimental treatment, the drug reduced the aggregation of inflammatory cells, but increased the size of the helminth, its reproductive function.
Prognosis and prevention
In the absence of complications, the prognosis is favorable, there are no data on the fatal outcomes of clonorchiasiso. According to WHO recommendations, in areas where more than 20% of the population is affected, annual preventive treatment of residents should be carried out. The vaccine has not been developed, some studies indicate a positive immunological effect when irradiated metacercariae are administered to mice. Non-specific protective measures include refusal to eat raw and insufficiently thermally treated freshwater fish and shellfish, early initiation of treatment of patients, control over water supply and sanitation systems.