Visceral Schistosomiasis

Introduction to visceral schistosomiasis The skin manifestations of visceral schistosomiasis (Viscera Schistosomiasis) may begin with mild erythema or papules on the feet and other parts of the scorpion-contaminated water source. This type of schistosomiasis can infiltrate the blood system and even settle in the bladder or small intestine. The venous system. After an incubation cycle, sudden fever, chills, pneumonia, and eosinophilia may occur, and anemia may also occur. basic knowledge The proportion of illness: 0.001% Susceptible people: no special people Mode of infection: contact with infected water Complications: upper gastrointestinal bleeding, ascites, hepatic encephalopathy, acute appendicitis, incomplete intestinal obstruction, colon cancer

The cause of visceral schistosomiasis

(1) Causes of the disease

The skin manifestations of visceral schistosomiasis (Viscera Schistosomiasis) may begin with mild erythema or papules on the feet and other parts of the scorpion-contaminated water source. This type of schistosomiasis can penetrate the blood system and even settle in the bladder or The venous system of the small intestine.

(two) pathogenesis

1. Schistosomiasis japonica

Early pathological changes are mainly caused by eggs, and Schistosoma mansoni egg granuloma has been shown to be a delayed type of cell-mediated allergic reaction, sensitized by the hairy exudates (soluble egg antigen) in mature eggs. T cells, caused by the release of various lymphokine factors, the immunopathological changes of schistosomiasis are more complicated. Due to the large number of eggs deposited in the tissues, the granuloma formed is larger, the surrounding cells infiltrate more, and the cell composition Different from Schistosoma mansoni granuloma, there are a large number of monocytes (plasma cells) and neutrophil infiltration in early lesions, and high concentrations of soluble egg antigens can be detected in Schistosoma japonicum granuloma. There is an eosinophilic radiation-like stick around the egg, which is an immune complex that binds antigen to the antibody. It is called Hoeplli phenomenon. The positive rate of circulating immune complexes and heterophilic antibodies in the blood of patients with acute schistosomiasis is very high, so acute schistosomiasis Disease is a mixed manifestation of cellular and humoral immune responses; and immunopathological changes in chronic and advanced schistosomiasis were thought to belong to late-onset cellular allergies, recently It is believed that mainly due to the disorder of cytokine network, liver fibrosis caused by schistosomiasis is produced on the basis of granuloma. Soluble egg factor, macrophage and T cell all produce fibroblast stimulating factor, which promotes fibroblast proliferation. Collagen synthesis, schistosomiasis fibrosis collagen type is mainly type I, III, late schistosomiasis liver collagen is mainly type I, type I collagen fiber inter-fork connection is strong, constitutes irreversible coarse fiber bundle, and type III collagen is small Fiber, which is easily degraded by collagenase, in addition, fibronetin and laminin in the extracellular matrix are non-collagen glycoproteins, and fibronectin mediates the binding of fibroblasts to collagen. It forms the connective tissue matrix, and laminin complements the adhesion function of fibronectin.

Part of the immunity can be obtained after the human body is infected with schistosomiasis. This is a kind of concomitant immunity, that is, there are still adult parasites and spawning in the portal vein of the patient, but there is certain immunity to reinfection, and this immunity does not damage the adult body in the body. It has been proved that the surface of the schistosomiasis cortex is covered with host antigen. Because it has antigenic camouflage and escapes the immune attack, it can be parasitized for a long time. Animal experiments prove that the resistance to reinfection of cercariae cercariae depends on the body fluid immunity. In addition to antibodies, the main effector cells are eosinophils, which synergistically kill larvae that invade the skin and are therefore antibody-dependent eosinophil-mediated cytotoxicity.

2. Pathology

Schistosoma japonicum mainly parasitizes in the inferior mesenteric vein and the supraorbital supraorbital vein. The eggs are deposited in the submucosal layer of the intestinal wall, and the portal vein blood flows to the branches of the liver. Therefore, the lesions are most prominent in the liver and colon.

(1) Colonic lesions: mainly in the rectum, sigmoid colon and descending colon, right colon and appendix are also often involved, acute lesions are mucosal congestion, edema, submucosal accumulation of egg nodules, formation of superficial after collapse Ulcer, discharge pus and blood, chronic period due to fibrous tissue hyperplasia, thickening of the intestinal wall, and can cause polypoid hyperplasia and colon stenosis, mesenteric thickening and shortening, omental tangles into a mass and other lesions.

(2) Liver lesions: early liver enlargement, miliary yellow granules (worm egg nodules) on the surface; fibrous tissue proliferation around the endovascular branch of the liver and the portal vein, causing fibrous lesions, producing trunk cirrhosis, liver surface There are many miliary nodules and connective tissue grooves, which are characterized by hardening around the portal vein of the liver, resulting in portal vein obstruction. The obstruction is often preceded by the hepatic sinusoid, and there is also a change in the hepatic sinus. Hypertension, portal vein obstruction and hemodynamic changes caused by high pressure, first of all, spleen due to obstructive hyperemia, long-term congestion caused by fibrous tissue hyperplasia, and hypersplenism, and second, portal vein occlusion can make portal-cavity collateral circulation Open, abdominal wall vein dilatation, especially in the lower end of the esophagus and gastric fundus varices, causing massive bleeding in the upper digestive tract after rupture.

(3) ectopic damage: refers to the disease of the eggs or (and) adult vagus and parasitic outside the portal system. Although the organs in the human body occasionally see the deposition of eggs, the lungs and brain are more common, the lungs The lesions were interstitial miliary granuloma with surrounding alveolar effusion. It was reported that male and female adult parasites were found in autopsy and animal pulmonary arteries. The granuloma of brain granuloma was located in the parietal and temporal lobe. At the gray matter junction of the brain, but no adult insects have been found in the cerebral veins during autopsy and surgery.

Visceral schistosomiasis prevention

According to the specific conditions of the epidemic areas, prevention and control should be carried out according to local conditions, and comprehensive measures combining manure and water source management and personal protection should be adopted to focus on the elimination of snails and general treatment of sick animals.

1. Control the source of infection

In the popular area, a large-scale simultaneous treatment of patients and diseased cattle, the use of praziquantel to expand chemotherapy to control the schistosomiasis epidemic, can significantly reduce the number of patients, which is an important part of the overall prevention and treatment work, especially in The lake and marsh area and the mountain area will have significant effects after 3 consecutive years. The schistosomiasis of the cattle can be 1.5~2mg/kg body weight of the suspension of nitric thiocyanamide.

2. Cut off the route of transmission

Before the snail is extinguished, the snail condition should be firstly clarified, and the snail map should be established. In order to provide the basis for the snail-killing plan, the physical snails such as the soil burial method that can change the environment of the snail snail can be adopted in the water network area, and the dam can be used in the lake and marsh area. , cofferdams, planting methods, the establishment of anti-snails around the residential area, chemical snails can be combined with physical snails, using niclosamide and other snail-killing drugs, and can be made into a sustained release agent to extend its snail-killing The effect, but most of the current chlorinating agents are harmless to crops, humans and animals, but they are toxic to fish and should be protected from water pollution.

Manure management: prevent human feces and livestock manure from polluting the water source, and treat it to make it harmless. For example, it should be sealed after 1:5 mixing of feces and urine, precipitation fermentation, storage in summer for 3 to 5 days, and winter 7 to 10 days. Dead blood trematode eggs, in addition, the use of biogas septic tanks in rural areas should be vigorously promoted.

Water source management: Protect the water source from pollution, promote the use of water, or use the river water for 3 days, if necessary, use chlorine-containing lime, add 1g per water (about 50kg), and use it after disinfection for 15min.

3. Strengthen personal protection and protect susceptible people

(1) The key lies in publicity and education: to guide people to pay attention to self-protection, and to avoid contact with infected water in popular areas. For example, children are strictly forbidden to play in the river ditch, and when the lake and the marsh area are harvested, the lake grass must be exposed to the infected water. Take personal protective measures, use fatty acid as matrix, add alkali to saponification, add niclosamide (2%) and turpentine to make protective agent, kill cercaria, 1% niclosamide alkaline solution impregnated underwear It also has a preventive effect on the cercaria.

(2) Preventive medication: Artemisin derivatives artemether and artesunate can kill schistosomiasis worms for 5 to 21 days. Artemisin ether usage: 15 days after exposure to infected water Take once with artemether (6 mg/kg each time), once every 15 days, and take 4 to 10 times. Artesunate usage: Take artesunate once every 7 days after exposure to the water. 6mg/kg), 1 time/week, and even 8 to 15 times, can effectively prevent schistosomiasis infection. According to 1996-1998, it has promoted the application of artesunate in Jiangxi, Anhui and Hubei provinces, preventing nearly 200,000 drugs. The population has a protection rate of 88.2% to 100%; artemether has also been used in more than 2,000 people (1994-1996) in the above areas, and its protection rate has reached 60% to 100%.

Visceral schistosomiasis complications Complications upper gastrointestinal bleeding ascites hepatic encephalopathy acute appendicitis incomplete intestinal obstruction colon cancer

1. Hepatic fibrosis complications

Patients with advanced schistosomiasis complicated by lower esophageal varices or more than 2/3 of the varices, and variceal rupture caused by upper gastrointestinal bleeding accounted for 16.5% to 31.6%, which is the main complication of schistosomiasis fibrosis, the clinical symptoms are a large number of Hematemesis and black feces can cause blood pressure drop and hemorrhagic shock, the mortality rate is about 15%, about half of the patients have repeated hemorrhage history, ascites or hepatic encephalopathy can occur after massive hemorrhage of the upper digestive tract, hepatic encephalopathy in the late stage Schistosomiasis is less than portal vein and cirrhosis after necrosis. Domestic reports account for 1.6% to 5.4%, and its course of disease is also longer. In addition, advanced schistosomiasis ascites complicated with primary peritonitis and Gram-negative bacilli sepsis are not. Rare.

2. Intestinal complications

In patients with endemic areas, the schistosomiasis can be found in the appendix specimens up to 31%, which is often a cause of acute appendicitis, and the appendix is easier to wear, and can be complicated by peritonitis or localized abscess.

Intestinal stenosis caused by severe colonic disease caused by schistosomiasis, may be complicated by incomplete intestinal obstruction, which is located in the sigmoid colon and rectum. In addition, the mesenteric and omental lesions may adhere to a mass, forming an intra-abdominal mass, schistosomiasis Colonic granuloma can be complicated by colon cancer. The patients are younger, mostly adenocarcinoma, with a lower degree of malignancy and a later metastasis.

Visceral schistosomiasis symptoms common symptoms diarrhea herpes herpes genital warts

Skin schistosomiasis most commonly affects the genitals, the anus, usually caused by Schistosoma japonicum or Schistosoma mansoni, in the groin, external genitalia, buttocks, anal lumps or wet sinus lesions, or cellular sinus.

Eggs can also be deposited on the skin and other parts, more common in the umbilical cord, some cases are staged or herpes zoster-like distribution, the primary lesion is a hard fleshy papule, oval, 2 to 3 mm in diameter, more An irregular plaque with a small uplift of papules, the color gradually deepens, and papillary hyperplasia occurs.

Examination of visceral schistosomiasis

Schistosomiasis eggs were found in urine, feces or rectal biopsy specimens.

Blood picture

The blood picture of patients with acute schistosomiasis is characterized by a significant increase in eosinophils. The total number of white blood cells is between (10 ~ 30) × 109 / L, eosinophils generally account for 20% ~ 40%, up to 90%, but very Eosinophils in patients with severe acute schistosomiasis often do not increase or even disappear, and instead of neutrophils, chronic eosinophils are still slightly increased, and in the advanced stage, due to hypersplenism, white blood cells and thrombocytopenia And have varying degrees of anemia.

2. Liver function test

In patients with acute schistosomiasis, serum globulin is significantly increased, serum alanine transaminase (ALT) is also slightly increased, and serum albumin is significantly reduced in patients with advanced liver disease due to liver fibrosis or cirrhosis, and often has a ratio of albumin to globulin. Inversion, the liver function tests of chronic schistosomiasis, especially asymptomatic patients, are mostly normal.

3. Liver imaging examination

It has important reference value for disease assessment.

(1) B-mode ultrasound examination: The degree of liver fibrosis can be judged from the B-ultrasound image, showing that the echogenic band of the portal vein wall is enhanced (6mm): it is linear in the shape of the line; the tube is the moderate; the mesh is the separator. To be severe, the latter gives liver surface nodules and splenomegaly in the combined image, suggesting liver fibrosis.

(2) CT scan: the liver capsule and the intrahepatic portal vein area of patients with advanced schistosomiasis often have calcification, CT scan shows a more specific phenomenon; liver capsule thickening calcification, perpendicular to the intrahepatic calcification septum; at the junction of the two There is a notch formation at the site, and severe liver fibrosis can be expressed as a turtle-like image.

pathology:

Schistosoma japonicum mainly parasitizes in the inferior mesenteric vein and the supraorbital supraorbital vein. The eggs are deposited in the submucosal layer of the intestinal wall, and the portal vein blood flows to the branches of the liver. Therefore, the lesions are most prominent in the liver and colon.

Diagnosis and identification of visceral schistosomiasis

diagnosis

In addition to the current clinical symptoms of epidemiological history, the diagnosis relies mainly on laboratory tests.

1. Parasitological diagnosis

Fecal smear examination is simple and easy, but in addition to patients with severe diarrhea, the positive rate of eggs is not high. The count of eggs in the feces can be determined by Kato-Katz collection method, 50mg fecal insects. Egg number <100 is mild; 100-400 is moderate; >400 is severe.

In China, fresh egg droppings have been used to precipitate the eggs and eggs, and the use of nylon bags to collect eggs and save the seeds can save manpower, time and equipment, and improve the positive rate of detection. The diagnostic method of stool examination has certain limitations, light type. The number of eggs discharged from the feces is small, and it occurs intermittently. It needs repeated examinations. The advanced schistosomiasis is not easy to be discharged from the intestinal wall due to fibrosis of the intestinal wall, so the positive rate is very low.

Rectal mucosa biopsy: taking a colonoscopy, taking the size of the mucosa from the lesion placed between the two slides, under the microscope, found that the positive rate of schistosomiasis eggs is very high, the eggs seen are mostly black eggs and empty Egg shells, eggs containing mature active ticks are rare, and can not be distinguished from long-term degenerative eggs, so it is not possible to assess the efficacy or as a basis for re-treatment. Prevention of major bleeding and perforation risk during biopsy operations, especially in patients with advanced schistosomiasis.

2. Immunological diagnosis

There are many methods, including intradermal testing and serum immunological tests for detecting adult, worm, cercaria and egg antibodies; such as ring egg precipitation test, indirect phosphor test, enzyme-linked immunosorbent assay, cerebral palpebral test, etc., immunological examination The method has high sensitivity and specificity, and has the advantages of simple blood collection and simple operation. However, since the antibody in the serum of the patient lasts for a long time after the cure, it cannot distinguish the past infection from the current patient, and has a false negative and false positive. And the shortcomings of cross-reaction with other trematodes, in recent years, the use of monoclonal antibodies to detect circulating antigen in patients with blood micro-method may diagnose active infections, and can be used as a reference for assessment of efficacy, is the current development of immunological diagnosis.

Urinary, fecal or rectal biopsy specimens are characteristic of schistosomiasis, and serological tests can be used for screening.

Differential diagnosis

Acute schistosomiasis is misdiagnosed as typhoid fever, amoebic liver abscess, miliary tuberculosis, etc., and significant increase in eosinophils in blood has important differential diagnostic value. It cannot be ignored. Chronic schistosomiasis liver splenomegaly should be associated with no jaundice virus. Identification of sexual hepatitis, the latter's loss of appetite, fatigue, liver pain and liver function impairment are more obvious, acute and a few patients with chronic schistosomiasis may have false positive HBsAg (RPHA method), and related to heterophilic antibodies, so serum should be checked at the same time Other hepatitis B signs or not using RPHA method, schistosomiasis patients have diarrhea, blood in the feces of stools are positive, and the number of hairy mites is more, easy to distinguish from amoebic dysentery, chronic dysentery, advanced schistosomiasis and portal vein And the identification of liver cirrhosis after necrosis: the former often has chronic diarrhea and blood history, portal vein hypertension caused by splenomegaly and lower esophageal varices are more common, liver function damage is lighter, jaundice, spider mites and liver palm are less common, but still need It can be identified by relying on multiple pathogens and immunological tests. It should be noted that schistosomiasis with hepatitis B in the endemic area is more common in China. See, in addition, in patients with epilepsy in endemic areas should be possible except brain schistosomiasis.

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