Schistosomiasis

Introduction to schistosomiasis Schistosomiasis is a local disease caused by parasitic worms in the human body. It is mainly prevalent in 73 countries in Asia, Africa and Latin America, with about 200 million patients. The pathological changes of schistosomiasis are mainly caused by eggs. The eggs are mainly deposited in the liver of the host and the intestinal wall of the colon. The granuloma and fibrosis caused by it are the main lesions of schistosomiasis. The formation of egg granuloma is an immune response of the host to the causative agent. On the one hand, the granuloma reaction destroys the eggs, and can isolate and remove the antigen released by the eggs, reduce the formation of antigen-antibody complexes in the blood circulation and damage to the body; on the other hand, the granuloma reaction destroys the normal host Tissue, the continually generated egg granuloma forms interconnected scars, leading to a series of lesions such as trunk cirrhosis and intestinal fibrosis. basic knowledge The proportion of illness: 0.0025% Susceptible people: no specific population Mode of infection: fecal-mouth transmission Complications: acute diffuse peritonitis

Cause of schistosomiasis

Pathogenesis

The cercaria can cause dermatitis through the skin, and localized papules and itching are an immediate and delayed type of allergic reaction.

When the child worm moves in the host, the organs (especially the lungs) undergo vasculitis, capillary embolization, rupture, local cell infiltration and punctiform hemorrhage. When a large number of children's worms move in the human body, the patient may have fever, cough, blood in the sputum, and eosinophilia, which may be an allergic reaction caused by local inflammation and metabolites of the worm.

Adults generally have no obvious pathogenic effects, and a few can cause mild mechanical damage, such as endometritis. However, its metabolites, worm secretions, excretions, and epidermal membranes that are exfoliated by the outer cortex of the worm can form immune complexes in the body and cause damage to the host.

The pathological changes of schistosomiasis are mainly caused by eggs. The eggs are mainly deposited in the liver of the host and the intestinal wall of the colon. The granuloma and fibrosis caused by it are the main lesions of schistosomiasis.

The formation of egg granuloma is an immune response of the host to the causative agent. On the one hand, the granuloma reaction destroys the eggs, and can isolate and remove the antigen released by the eggs, reduce the formation of antigen-antibody complexes in the blood circulation and damage to the body; on the other hand, the granuloma reaction destroys the normal host Tissue, the continually generated egg granuloma forms interconnected scars, leading to a series of lesions such as trunk cirrhosis and intestinal fibrosis.

Schistosomiasis egg granuloma forms in the blood vessels of tissues, blocks blood vessels, destroys blood vessel structure, and causes tissue fibrosis. Such lesions are mainly found in organs with more egg deposits, such as liver and colon. In the liver, the egg granuloma is located at the terminal branch of the portal vein and the anterior sinus vein, so the structure and function of the liver are generally unaffected. In patients with severe infection, extensive fibrosis occurs around the portal vein. On the hepatic section, long and white fiber bundles around the portal vein are inserted into the liver from different angles. This is called pipestem fibrosis, which is characteristic of advanced schistosomiasis. Sexual lesions.

Schistosomiasis prevention

1 Do not swim in lakes, rivers, canals, and waters with snails.

2Because of the inevitable exposure to infected water in production and life, you can apply protective ointment before exposure to the infected water to prevent schistosomiasis infection.

3 After contact with the infected water, it is necessary to go to the local blood defense department for necessary examination and early treatment.

Schistosomiasis complications Complications, acute diffuse peritonitis

Complications are more common in chronic and advanced cases, with appendicitis more common.

Patients with schistosomiasis complicated with acute bacterial appendicitis may cause perforation, appendicitis abscess, deposition of eggs in appendicitis tissue, and perforation of appendix may cause complications of diffuse peritonitis.

In patients with schistosomiasis, colonic stenosis can occur when the colonic lesion is severe, causing difficulty in defecation and other symptoms of intestinal obstruction.

It is not uncommon to have cancer on the basis of intestinal proliferative lesions of schistosomiasis. The incidence of colon cancer in the epidemic area is higher than that in non-endemic areas. The age of onset is 30-40 years old, and many people aged 20-30. Schistosomiasis and colon cancer are mostly differentiated adenocarcinoma and mucinous adenocarcinoma. The clinical manifestations are mainly colon obstruction, blood in the stool and abdominal mass. The filling defects can be seen by X-ray examination of barium enema. The sigmoid colonoscopy and biopsy can confirm the diagnosis. .

Symptoms of schistosomiasis Common symptoms Weight loss chest pain gastrointestinal symptoms abdominal wall venous anger false tuberculosis nodules hepatosplenomegaly ascites

(1) Invasion period

Patients may have cough, chest pain, and occasionally bloodshots in the sputum.

(2) Acute phase

Clinically, it has the following characteristics:

1. Fever: the main symptoms of this period, the level of fever, the duration and heat type depending on the infection.

2. Gastrointestinal symptoms: often dysentery-like stools, can carry blood and mucus.

3. Hepatosplenomegaly.

4. Pulmonary symptoms: Cough is quite common, and may have chest pain, blood stasis and other symptoms.

(C) Chronic phase: Many cases have not been found in the acute phase, untreated or incomplete treatment, or repeated infections for several times, and gradually developed into chronic, generally lasting 10 to 20 years, due to its long course, symptoms Light weight can vary greatly.

(D) Late: the patient is extremely thin, with severe symptoms such as ascites, spleen, and abdominal wall venous anger.

Examination of schistosomiasis

an examination

Fecal sedimentation hatching test: The hatching method is currently the most important diagnostic method.

Colonoscopy and intestinal mucosal biopsy: Suspected schistosomiasis and repeated stool examination for negative eggs is suitable for colonoscopy.

Blood: The total number of white blood cells and eosinophils in the acute phase increased significantly.

Auxiliary inspection

1. Pathogen diagnosis

Check the eggs from the feces or the hatching mites and the rectal mucosa. There are: (1) direct smear method: sputum eggs can often be detected in the mucus blood of patients with severely infected areas or acute schistosomiasis, and the method is simple and convenient. The detection rate of eggs is low, (2) the hatching method can increase the positive detection rate, (3) the quantitative transparent method: used as the count of schistosomiasis eggs, (4) the rectal mucosa biopsy: the thickening of the intestinal wall of patients with chronic and advanced schistosomiasis, insects Egg discharge is blocked, so it is not easy to find eggs in the feces, and colonoscopy can be applied.

2. Immunodiagnosis

(1) Intradermal test (IDT): The coincidence rate between the general intradermal test and the fecal test egg positive is about 90%, but false positive or false negative reaction may occur, and high cross-reactivity may occur with other trematode diseases. And the patient can still be positive after many years of cure. This method is simple and rapid, and is usually used for on-site screening of suspicious cases.

(2) Detection antibody: There are specific antibodies in the serum of blood-sucking patients, including IgM, IgG, IgE, etc. If the subject is not treated with pathogens, and the specific antibody is positive, it is of great significance for determining the diagnosis; if the pathogen has been treated The specific antibody is positive, and it is not certain that there is still adult parasitic in the subject. After the cure, the specific antibody can still be maintained in the body for a long time. Currently, there are many serological diagnostic methods for detecting schistosomiasis of antibodies, and the following are commonly used. Several: 1) Circunoval precipitin test (COPT): 100 eggs are usually examined, and the positive number of eggs (cyclin rate) is equal to or greater than 5%, which is positive, and the fecal schistosomiasis is positive. The positive rate of COPT was 97.3% (94.1%-100%). 2) Indirecthaemagglutination test (IHA): The positive rate of positive sputum sputum eggs positive with IHA was 92.3%100%, normal people The false positive rate is about 2%, and there may be false positive reactions with paragonimiasis, Clonorchis sinensis, and Trichinella infection. IHA is easy to operate, with less blood, and the results are interpreted. At present, it has been widely used in China. 3) Enzyme-linked immunosorbent assay (ELISA): This test has high sensitivity and specificity, and can reflect antibody levels. The positive detection rate is 95%-100. %, the false positive rate was 2.6%, the patient was negative from 50% to 70% half a year to one year after praziquantel treatment, and 4) immunoenzymicstaining test (IEST).

It is worth mentioning that in recent years, with the development of science and technology, some high-tech and new methods have been gradually introduced into the field of diagnosis and research of schistosomiasis, such as immunoblotting (western blot), which is in protein gel. Based on electrophoresis and solid-phase immunoassay, a new molecular immunology technology has been developed to promote the progress of serological diagnosis of schistosomiasis. It can not only analyze and identify the restricted components of schistosomiasis antigens. Moreover, it can be used for diagnosing patients and distinguishing different serological stages of schistosomiasis, and for the preparation of monoclonal antibodies (McAb) by hybridoma technology, using a specific McAb to purify schistosomiasis antigen for serological diagnosis of schistosomiasis McAb can also be used to detect circulating antigens, providing a new way to diagnose schistosomiasis.

(3) Detection of circulating antigen: Since the antibody remains in the host for a long time after treatment, the positive result often cannot distinguish between the current infection and the previous infection, and it is not easy to evaluate the curative effect. The circulating antigen is the macromolecule discharged from the living body to the host. Microparticles, mainly excreted by worms, have antigenic properties in secretion or epidermal exfoliation, and can be detected by serum immunology tests. In theory, CAg detection has its own superiority, which not only reflects activity Infection, and can evaluate the efficacy and estimate the species.

Diagnosis and identification of schistosomiasis

diagnosis

The diagnosis of schistosomiasis includes two major parts: pathogen diagnosis and immunodiagnosis. The patient's diagnosis requires the detection of eggs or hatching of the mites from the feces. As the blood-defense work progresses, the difficulty of the fecal test eggs increases, so the examination method is continuously improved, and a series of serological diagnosis methods are proposed. These methods are becoming more and more perfect. Simple and effective.

Differential diagnosis

1. Acute schistosomiasis: must be differentiated from sepsis, malaria, typhoid and paratyphoid fever, acute miliary tuberculosis, viral infection, and other intestinal diseases, mainly based on birthplace, occupation, epidemic season, history of exposure to water, hyperthermia, hepatomegaly Tenderness, eosinophilia, and positive stool incubation are the main points of identification.

2. Chronic schistosomiasis: It must be differentiated from chronic bacillary dysentery, amoebic dysentery, ulcerative colitis, intestinal tuberculosis, rectal cancer, etc., fecal sputum sputum sputum positive can be diagnosed, eosinophil proliferation contributes to the disease Diagnosis, colonoscopy and tissue examination can help to confirm the diagnosis, routine examination of stool, culture, X-ray barium enema, diagnostic treatment is helpful for diagnosis and differential diagnosis.

3. Advanced schistosomiasis: identification of cirrhosis caused by portal cirrhosis and other causes, hepatosplenomegaly caused by portal hypertension caused by cirrhosis of schistosomiasis, ascites (spleen), abdominal wall vein The change of anger is more prominent, the function of liver cells is lighter, the surface of the liver is uneven, and the cirrhosis of the portal vein is weak, anorexia, jaundice, vasospasm, hepatomegaly is significantly reduced or even reduced, and it is difficult to touch the surface nodules. Active liver function changes, such as increased transaminase.

4. Heterotopic schistosomiasis: pulmonary schistosomiasis must be differentiated from bronchitis, miliary tuberculosis, and paragonimiasis. Acute cerebral schistosomiasis should be differentiated from epidemic encephalitis. Chronic cerebral schistosomiasis should be differentiated from brain tumors and epilepsy.

Otitis dermatitis needs to be differentiated from rice dermatitis. Rice dermatitis is caused by the parasitic cercariae of the animal in the portal vein of animals such as cattle, sheep and ducks. It is more common in the southeast, northeast and southwestern provinces of China. The host ovulates into the water and hatches the edulis. Into the cone, the snail enters the snail, and the snail escapes immediately after the human touches the cercaria, causing dermatitis. The dermatitis is red at the beginning, gradually expanding into a red papule. The rash subsides after one week, and the cercaria is eliminated. Develop again.

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