Schistosomiasis japonicum

Introduction to Schistosomiasis Japonica Schistosomiasisjaponica is a disease caused by Schistosoma japonicum parasitic in the portal system. It is infected by skin contact with water containing cercariae. The main lesion is granuloma caused by eggs in the liver and colon. In the acute phase, there is fever, hepatomegaly and tenderness with diarrhea or discharge of pus and blood and eosinophils in the blood; chronic splenomegaly is the main stage; late stage is mainly fibrotic lesions around the portal vein, developing portal vein High pressure, spleen and ascites. basic knowledge Sickness ratio: 0.05% Susceptible people: no special people Mode of infection: digestive tract spread Complications: liver fibrosis, hepatic encephalopathy, sepsis, colon cancer

The cause of schistosomiasis in Japan

( 1 ) Causes of the disease

Schistosoma japonicum is dioecious, often together, parasitic in the portal system, mainly in the human inferior mesenteric vein ( Figure 1) , the survival time is about 4 to 5 years, but the elderly can reach 10 years or more, the female is in the intestinal wall In the submucosal peripheral veins, one female can lay about 1000 eggs per day. After the eggs excreted from the feces enter the water , the edulis are hatched at a suitable temperature (25 to 30 °C ) , and the edulis are straight under the water surface. Activity, invade the intermediate host snail, develop in the snail, develop and multiply through the mother cell and the scorpion scorpion, and the cercaria will continue to escape after about 7-8 weeks, ranging from dozens to more than 100 pieces per day. Bifurcation, with water flowing on the surface of the water, when people, animals contact with the water, the cercaria quickly (as short as 10s) invade from the skin or mucous membranes, the invaders of the child's worms flow through the lungs and reach the liver, develop to 15 ~ 16 days, starting the male and female embrace, about 1 month or so in the liver developed into adults, reverse blood flow to the peripheral blood vessels of the inferior mesenteric vein to lay eggs, complete their life history.

In the life history of Schistosoma japonicum, human beings are the ultimate host, and snails are the only intermediate host necessary. Schistosoma japonicum has a wide range of animal storage hosts in nature, such as cattle, pigs, sheep, dogs, cats, etc., as well as various wild animals such as rats. Wait, a total of more than 40 , can be its ultimate host.

( two ) pathogenesis

Pathogenesis

The early pathological changes of schistosomiasis in Japan are mainly caused by its eggs. The granuloma of Schistosoma mansoni has been proved to be a delayed type of cell-mediated allergic reaction, which is derived from the hairy exudates of mature eggs ( soluble egg antigen). Sensitized 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 and the surrounding cells infiltrate more. Moreover, the cell composition is different from that of Schistosoma mansoni egg granuloma. In the early lesions, there are a large number of monocytes ( plasma cells ) and neutrophil infiltration, and high concentrations of soluble insects can be detected in Schistosoma japonicum granuloma. Egg antigen, an eosinophilic radiation-like stick around the egg, an immune complex that binds the antigen to the antibody, called Hoeplli phenomenon, and the positive rate of circulating immune complexes and heterophilic antibodies detected in the blood of patients with acute schistosomiasis is very high. Therefore, acute schistosomiasis is a mixed manifestation of cellular and humoral immune responses ; and immunopathological changes of chronic and advanced schistosomiasis are thought to belong to late-onset cells. Allergic reactions have recently been thought to be mainly due to cytokine network disorders. Liver fibrosis caused by schistosomiasis is produced on the basis of granuloma. Soluble egg factors, macrophages and T cells all produce fibroblast stimulating factors. Fibroblast proliferation and 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 is firmly connected, constitutes irreversible coarse fiber bundle, and III Collagen is a fine fiber that is easily degraded by collagenase. In addition, fibronectin and laminin (1aminin) are non-collagen glycoproteins in extracellular matrix, and fibronectin mediates fibroblasts and collagen. Proteins combine to form a connective tissue matrix, while laminin complements the adhesion 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 open the portal - cavity collateral circulation The abdominal wall vein is dilated, especially in the lower end of the esophagus and the fundus varices. After rupture, it causes massive bleeding in the upper digestive tract.

(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.

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 Lakes and mountain areas will have significant results after three consecutive years. The schistosomiasis of cattle can be 1.5~2 mg/kg body weight of nitric thiocyanamide suspension. One intravenous injection has good curative effect.

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 mixing 1:5 of feces and urine, precipitated and fermented, stored in summer for 3 to 5 days, and in winter for 7 to 10 days, it can be killed. 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 clean water, or store the river water for 3 days. If necessary, use chlorine-containing lime, add 1g per water (about 50kg), and use it after disinfection for 15 minutes.

3. Strengthen personal protection and protect susceptible people

(1) The key lies in propaganda and education, guiding people to pay attention to self-protection, and avoiding contact with infected water in popular areas. For example, children are strictly prohibited from playing in the river ditch. When harvesting and harvesting in lakes and lakes, lakes and grasses must be exposed to 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 1 artemether (6mg/kg each time), 1 time / 15 days, and then take 4 to 10 times. Artesunate usage: Take artesunate once every 7 days after exposure to the water. The second 6 mg / kg), the next 1 / week, and even served 8 to 15 times, can effectively prevent schistosomiasis infection, according to 1996-1998 in Jiangxi, Anhui, Hubei Province, the promotion of the application of artesunate, prevent medication near The protection rate of 200,000 people is 88.2%-100%. Artemether has also been used in more than 2,000 people in the above areas (1994-1996), and its protection rate is also 60%-100%.

Schistosomiasis complications in Japan Complications liver fibrosis hepatic encephalopathy sepsis 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 schistosomiasis caused by severe colonic lesions may be complicated by incomplete intestinal obstruction, which is located in the sigmoid colon and rectum. In addition, 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.

Symptoms of schistosomiasis in Japan Common symptoms High fever, low heat, heat retention, heat, heat, tendency, constipation, abdominal pain, diarrhea, hypoproteinemia, bloating

The clinical manifestations of schistosomiasis are complex and diverse. They are classified into acute, chronic, and advanced trematode diseases and ectopic lesions according to the early and late stages of infection, the severity of infection, the deposition of eggs and the immune response of the human body.

Acute schistosomiasis

Occurred in summer and autumn, from July to September is common, male young adults and children are mostly, patients often have a clear history of contact with water, such as playing lake grass, fishing, crab, swimming, etc., often for the first time severe infection, about Half of the patients had bite-like red lesions at the site of the cercaria invasion, which resolved spontaneously within 2 to 3 days. The length of incubation from the cercaria to the clinical stage was different (23-73 days), but it took up about 1 month. The disease is more urgent, and the systemic symptoms and fever are the main systemic reactions.

(1) Fever: patients have fever, high fever, the duration is proportional to the degree of infection, the hot type is the most common intermittent type, the body temperature curve is jagged, late night high fever, with chills, the second morning heat retreat, sweat Zhang heat and irregular hypothermia; rare heat is rare, patients are generally no significant symptoms of hyperemia, but severe patients can be consciously indifferent, heavy hearing, abdominal distension, etc., relatively slow pulse can also be seen, it is easy to be misdiagnosed as typhoid, Short-term fever is only 2 weeks, but most of them are about 1 month. Severe patients can have fever for several months, which is called severely delayed type, accompanied by severe anemia, weight loss, edema, and even cachexia.

(2) allergic reactions: urticaria, angioedema, mild lymph nodes, etc., urticaria is more common, about one-third of patients, eosinophils in blood often increase significantly, with important diagnostic reference value.

(3) Abdominal symptoms: More than half of the patients in the course of the disease have abdominal pain and diarrhea, while only 10% of patients with pus and blood are discharged. The number of diarrhea is not much, sometimes alternating with constipation. The severe patient has tenderness and flexibility in the abdomen, and there may be ascites.

(4) Liver and splenomegaly: More than 90% of patients have enlarged liver, accompanied by varying degrees of tenderness, especially in the left lobe. The jaundice is rare, and about half of the patients have mild splenomegaly.

2. Chronic schistosomiasis

It accounts for the vast majority in popular areas.

(1) Asymptomatic patients: The most common symptoms of chronic schistosomiasis are found only in the case of fecal screening or medical treatment for other diseases.

(2) Symptomatic patients: abdominal pain, diarrhea is common, two or three times a day loose stools, occasionally with blood, when the time is on, heavy patients have persistent pus and blood, accompanied by heavy, chronic schistosomiasis patients often have liver The splenomegaly is mainly caused by hepatomegaly in the early stage of the disease, especially in the left lobe of the liver. However, as the disease progresses, the spleen gradually enlarges, so it is called liver spleen schistosomiasis.

Stomach and duodenal schistosomiasis are rare. These patients are diagnosed by schistosomiasis eggs after surgery or gastroscopy.

3. Advanced schistosomiasis

Mainly refers to schistosomiasis liver fibrosis, according to its main clinical symptoms are divided into spleen, ascites and pygmy type, with the vigorous development and deepening of China's schistosomiasis work, patients receive timely treatment, the number of advanced schistosomiasis has been greatly reduced.

(1) Giant spleen type: the most common, accounting for the majority of advanced schistosomiasis, the lower edge of the spleen below the umbilical line, or the medial swelling beyond the midline, the texture is hard, often sputum and obvious trace, advanced schistosomiasis patients When massive hemorrhage occurs in the lower esophageal rupture, the spleen can be seen to shrink, and the spleen-type patients are accompanied by hypersplenism, white blood cells and thrombocytopenia, and anemia, which may have bleeding tendency.

(2) Ascites type: Ascites is a manifestation of significant loss of liver function in advanced schistosomiasis, ascites formation and portal vein obstruction, hypoproteinemia, and secondary aldosterone increase caused by water and sodium retention, and the degree of ascites varies. The course of the disease varies, the patient can complain of abdominal distension, abdominal distension, often umbilical hernia and abdominal wall varicose veins, sometimes continuous vascular murmur can be heard in the umbilical cord - Ke-Bao syndrome, a small number of patients appear mild Astragalus, spider mites and liver palm are less common than portal cirrhosis, and lower extremity edema is common.

(3) pygmy type: It is rare nowadays that children suffer from dwarfism due to repeated severe infection of liver growth regulator (somatomedin), which affects their growth and development. The pygmy type has a short stature, sexual organs are not developed, and testicles are small. , no menstruation, for pituitary dwarfism.

The above three types have a phenomenon of mutual existence.

4. Ectopic damage

(1) pulmonary schistosomiasis: more common in patients with acute schistosomiasis, is a worm, egg interstitial lesions caused by egg deposition, respiratory symptoms are mostly mild, and often covered by systemic symptoms, manifested as mild cough and chest pain, less The hemoptysis is rare, the lung signs are not obvious, and sometimes the dry and wet squeaks are heard. However, when the severe patients have extensive lesions in the lungs, the chest X-ray can be seen as diffuse cloud-like, patchy, miliary-like infiltrated shadows, blurred edges. In the middle and lower lung fields, the lung lesions gradually disappeared within 3 to 6 months after pathogenic treatment, and did not develop pulmonary heart disease.

(2) cerebral schistosomiasis: clinically can be divided into acute and chronic two types, both of which are more common in young and middle-aged patients. In the second world war, the US military infected schistosomiasis in the Philippines in 1200 cases, the incidence of cerebral schistosomiasis accounted for 2%, cerebral schistosomiasis in the course of acute schistosomiasis patients with symptoms of meningoencephalitis: disturbance of consciousness, meningeal irritation, convulsions, convulsions, hyperreflexia, pyramidal tract signs, etc., normal cerebrospinal fluid or mild protein and white blood cells Increased, the main symptoms of chronic type is seizures, especially localized epilepsy is more common, CT scan of the brain shows that the lesion is often located in the parietal lobe, also seen in the occipital lobe, unilateral multiple high-density nodule shadow, a few centimeters Size, but there is extensive cerebral edema around it, so that the brain is bulging, even pressing the lateral ventricle to deform it. The liver and splenomegaly of patients with cerebral schistosomiasis are sometimes not obvious. If the diagnosis and treatment are early, the prognosis is good. Rehabilitation, CT scan of the brain returned to normal, and epilepsy also stopped.

Examination of schistosomiasis in Japan

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

3.B type ultrasonic inspection

The degree of liver fibrosis can be judged from the B-ultrasound image, showing that the echogenic band of the portal vein is enhanced (6 mm): it is mild in the linear shape, moderate in the tubular shape, and severe in the reticular separation. Liver surface nodules and splenomegaly in the image may indicate liver fibrosis.

4.CT scan

In the patients with advanced schistosomiasis, the liver capsule and the intrahepatic portal vein often have calcification. The CT scan shows a more specific phenomenon; the liver capsule is thickened and calcified, perpendicular to the intrahepatic calcification septum; at the junction of the two, there is a notch formation. Severe liver fibrosis can be expressed as a turtle-like image.

Diagnosis and identification of schistosomiasis in Japan

diagnosis

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

1. Parasitological diagnosis Although the stool smear examination is simple and easy, except for 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. The number of eggs in the 50 mg feces is <100, 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. There are many immunological diagnostic methods, including intradermal tests 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 membrane test Etc., the immunological examination 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 False-negative, false-positive and cross-reactive with other trematodes. In recent years, the use of monoclonal antibodies to detect circulating antigens in patients with blood may be used to diagnose active infections, and can be used as a reference for assessment of efficacy. The trend.

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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