Echinococcosis granulosus

Introduction to echinococcosis Echinococcosis granulosa is a disease caused by the larvae of the human body infected with Echinococcus granulosus, also known as cystic echinococcosis. The dog is its final host. The sheep and the cow are the intermediate hosts. Therefore, the disease is prevalent in the livestock area. The human can also become the intermediate host due to the ingestion of eggs, and echinococcosis occurs. The hydatid cyst is most common in the liver, followed by the lungs, and other organs such as the brain and bones are occasionally violated. basic knowledge Sickness ratio: 0.0001% Susceptible people: no specific population Mode of transmission: insect vector transmission Complications: massive hemoptysis

The cause of echinococcosis

Causes:

Echinococcus granulosus is the smallest of all kinds of aphids. It is parasitic in the small intestine of dogs. The length of the worm is 2.5-6 mm. It consists of the head section, the neck, the immature section, the mature section and the gestational section. The head section is pear-shaped, with a apex and four suction cups. The apex is rich in muscle tissue and has strong telescopic force. There are two rings of 28 to 48 (usually 30 to 36) arranged in two radial rows. The structure of the nodule is similar to that of the tapeworm. The genital hole is located in the middle of the side of the segment, and the testicles are 45 to 65. They are distributed in the front and rear of the genital hole. The gestational section is the longest, which is equal to half of the body length. The genital opening is in the middle of one side of the segment. The uterus has irregular branches and collaterals (also called lateral sacs), which are filled with eggs (200-800), and release eggs after rupture in the intestine or intestine. .

The eggs are round, brownish yellow, with a double-layered embryonic membrane and a radiation pattern inside, containing six hooks. The shape is similar to that of beef aphids and pork aphid eggs. It is not easy to distinguish. The eggs are more resistant to the outside world at room temperature. Survival in water for 7 to 16 days, can survive for 11 to 12 days in a dry environment, and survive for 116 days at 0 °C. It is not easily killed by chemical insecticides in vegetables and fruits, boiled and exposed to direct sunlight (50 ° C) for 1 h. Eggs have a lethal effect.

Eggs are continuously excreted with dog feces, contaminating their skin, hair, pasture, barn, vegetables, soil, water, etc. After the eggs are swallowed by sheep or other intermediate hosts, they are hatched in the duodenum by digestive juice. Six hooks invade the peripheral veins of the intestinal wall, invade the liver and other internal organs with the blood flow of the portal vein, forming a hydatid cyst, and the hydatid cyst is swallowed by the dog. The head section develops into an adult in the small intestine of the dog for 3 to 10 weeks. figure 1).

Echinococcus granulosus is saclike, with the outer wall of the cornea and the inner surface of the hair mask (blast layer). There is a colorless transparent liquid in the capsule. It contains a small amount of protein, which is similar to the cerebrospinal fluid. The cortex is a white translucent film. , layered like powder skin, composed of secretions of germinal cells, has the function of protecting the hair-producing membrane, the hair-developing membrane is the worm itself, has significant reproductive ability, can be budded inward, forming the hair sac (the sac) and the original head, the hair follicles have pedicles connected with the hair mask, and the hair mask on the inner surface of the capsule wall forms many original head lice. The original cockroaches break into the sac fluid from the capsule wall, called the sac sand, which is the white fine particles visible to the naked eye. The hair follicles of the ascospore detached are free in the sac fluid. The structure of the ascus is the same as that of the mother sac, and the hair follicles (sun sacs) can be formed. Thus, the three generations of the ancestors and the ancestors are simultaneously present in one echidium sac, in the older package. There are hundreds of ascuss and tens of thousands of original mites in the sac. The hair styling film can occasionally grow out and grow into an exogenous sac. It is located between the cortex and the host capsule, and some hydatid sacs do not. Produce ascus, even without producing the original sputum, called sterility sac, package Most balloon unilocular, was more room for the resistance of the honeycomb by Echinococcus multilocularis, another system.

The terminal host and intermediate host of Echinococcus granulosus have a wide range. In China, the livestock life cycle between dogs and sheep is mainly caused. Adults are parasitic in the dog small intestine for 5 to 20 months or more, in addition to the above-mentioned livestock life cycle. In addition, there is a life cycle in which wolves, foxes, etc. are the final hosts and wild hoofed animals are the intermediate hosts, so this disease is also a natural epidemic disease.

Pathogenesis:

After the eggs of Echinococcus granulosus enter from the mouth, they are hatched by the gastrointestinal digestive juice. The part of the invading tissue is surrounded by local cells and destroyed. Some of them still survive and develop. First, the portal vein blood flow invades the liver, and most of them form a hydatid cyst in the liver; a few of the six hooks pass through the liver sinus, the hepatic vein, and the right heart invades the lung; through the pulmonary microvasculature, the left heart enters the systemic circulation and can spread throughout the body. Organs, so the hydatid can be parasitic on any part of the human body. According to 426 cases of Gansu Provincial People's Hospital and 895 cases of domestic comprehensive report, the distribution of hydatid cysts in the body is: liver 75%~78%; lung 8.5%~14.5%; brain 0.2%0.3%; spleen 1.3%2.7%; kidney 0.3%0.4%; bone 0.2%0.9%; female pelvic cavity 1.9%3.3%, the distribution of pediatric hydatid cyst is different from adult, brain worm The disease accounted for 3.5% to 4.3%, and the incidence of pulmonary hydatid cysts was also high. The six hooks developed to a diameter of 40 m on the 4th day after sinking in the liver, and cysts began to appear. The vesicles were visible at the third week. 250 m; 1 cm in the 5th month, and differentiated into the cornea and the hair growth membrane, after which the growth rate is about 1 mm / month, or 1 cm / year Usually hydatid cyst with symptoms of 10cm; cystic mass occurred up to 20cm, the lung hydatid faster growth, an annual increase of 4 ~ 6cm.

The hydatid cyst is divided into two inner and outer capsules, the inner capsule is the hydatid cyst, and the outer capsule is the fibrous envelope of the host. There is only mild adhesion between the two. The hepatic hydatid cyst is generally a large cyst, and the cyst fluid reaches hundreds to several. Thousand milliliters, hydatid cysts can be degraded by mechanical or chemical (biliary) damage or aging, at this time the outer capsule gradually thickens, and calcification can occur, more than 90% of adult patients with hepatic hydatid cysts contain ascus, and children More than 90% do not contain ascus, mainly related to the age of the insect.

The pathological changes of echinococcosis are mainly caused by the cystic space-occupying growth and compression of adjacent organs. When the liver hydatid sac gradually grows, the intrahepatic bile duct is compressed and entrapped in the outer wall, sometimes the bile duct is oppressive. Necrosis breaks into the cyst, which makes the ascus and cyst fluid yellow, and is easy to cause secondary bacterial infection. The lung hydatid cyst is mostly free of ascus, and can also break into the bronchus, and the corneal layer rotates and contracts, so that the inner surface is turned out. Occasionally, the hair growth layer is coughed out together with the head section and the cystic fluid. It is also prone to bacterial infection. If the hydatid cyst breaks into the bronchioles, the air may enter the inner and outer sacs, and it may be a crescent-shaped gas belt. A large number of cystic fluids in the sac and rupture into the body cavity (abdominal and thoracic cavity) can cause anaphylactic shock and secondary hydatid cysts.

Echinococcus granulosus prevention

Improve environmental sanitation, cultivate good hygiene habits, wash hands before meals, food should be cooked, do not drink raw water, raw milk, do not eat lettuce, avoid contact with dogs, especially important for children.

1. Health publicity and education: publicize the serious harm of echinococcosis to humans and animals, the way of infection and its prevention and control measures.

2. Control the source of infection to widely publicize the harm of raising dogs, because dogs can not only transmit echinococcosis, but also rabies, black fever, tsutsugamushi, etc. Wild dogs should be hunted, dogs that must be kept such as sheepdogs, police dogs, etc. Should be registered, regular quarantine, in the endemic area of echinococcosis, dogs should regularly take anthelmintic drugs such as praziquantel 5mg / kg body weight, Dayton, 1 / 6 weeks, dog feces should also be harmless treatment.

3. Do a good job of livestock grazing and rearing: the kennel should be separated from the sheep pen, pay attention to feed hygiene and cleansing the barn, and implement grazing in the four seasons, which can reduce infection. People and animals should use water to prevent water pollution.

4. Strictly implement veterinary health supervision: strengthen the meat inspection system, bury or burn the internal organs of the diseased sheep, or feed the sheep and goats after cooking. Under no circumstances should the viscera of the sick sheep be fed to the dog.

Complications of echinococcosis Complications

The main complications of liver hydatid disease are infection (16.2% to 26.9%) and rupture (4.3% to 11.5%), and large hemoptysis can occur.

Symptoms of Echinococcus granulosus Common symptoms Chest pain toxemia Sputum splenomegaly Rhubarb fistula Hypertension Pussy tremor Cough hemoptysis

The incubation period of cystic echinococcosis is lengthy. The clinical manifestation depends on its parasitic part. The size of the cyst varies with the presence or absence of complications. There is no symptom in the early stage of the disease, and the patient's overall health is good.

1. Hepatic cystic echinococcosis: the most common, mostly located in the right lobe (80% to 85%), often close to the liver surface, so the main symptom is a painless mass in the right upper abdomen or upper abdomen, the surface is smooth, the quality is firmer A very small number of patients (2% to 3%) can be exposed to hydatid tremor at the time of percussion. The impact of the capsules on each other causes the wall vibration. The left hepatic lobe of the patients with giant right lobe capsular sac often has compensatory swelling. The signs of the left leaf hydatid sac appear earlier and more prominent. The upward growth of the hydatid sac at the top of the right lobe of the liver causes the diaphragm to rise, which restricts the movement. The hepatic hydatid sac grows downward and is located near the hepatic sac. Common bile duct causes jaundice, or pressure portal vein causes portal hypertension: splenomegaly, lower esophageal varices or ascites, but less common, major complications of liver hydatid infection (16.2% to 26.9%) and rupture (4.3 %~11.5%), the two often cause each other:

(1) Most of the bacterial infections come from the bile duct, but also due to trauma or puncture. There is fever in the clinic, pain in the liver area, white blood cells and neutrophils, similar to liver abscess, but because of the thick outer wall, bacteria and toxins It is not easy to be absorbed into the blood, so the symptoms of toxemia are mild, and the infection of the echinococcal sac in the right lobe of the liver. In addition to the elevation of the diaphragm and the obstruction of movement, it can also cause reactive pleurisy and effusion.

(2) The perforation of hepatic hydatid cyst is a common and serious complication. The tension in the hydatid cyst is very high. The diagnostic puncture does not cause the cystic fluid to overflow. The rupture of the hydatid cyst can also be caused by trauma. A large amount of cystic fluid breaks into the abdominal cavity. Or the chest cavity can cause anaphylactic shock, and the first section of the cystic fluid can be transplanted and transplanted into the abdominal cavity or the thoracic cavity to produce multiple secondary hydatid cysts.

2. Lung cystic echinococcosis: the right lung (2/3) is more than the left lung, the lower middle lobe is more than the upper lobe, the early lung hydatid cyst is smaller, the patient has no symptoms, often found in chest X-ray. Lung hydatid cysts gradually grow up can cause chest pain, cough, blood stasis and other symptoms, chest pain is persistent pain, blood in the sputum is also more common (about 1/3), occasionally hemoptysis can occur when the hydatid cyst is ruptured About 1/3 of the patients have capsular sacs that penetrate the bronchus. When they break through, they suddenly develop paroxysmal cough, difficulty breathing, and a large amount of watery cyst fluid and powdery horny membrane and hemoptysis, occasionally due to a large amount of cyst fluid. When the occlusion causes suffocation and concurrent infection, the patient has symptoms such as fever, cough and sputum.

3. Cerebral cystic echinococcosis: the incidence rate is about 1%, more common in children, the parietal lobe is common, mostly accompanied by liver and lung hydatid disease, clinical symptoms are headache, optic disc edema and other intracranial hypertension, There are often seizures, EEG can be seen in localized slow wave, CT scan of the brain and magnetic resonance imaging can show large cyst shadows, and have the value of localization and qualitative diagnosis.

Echinococcus granulosus in other organs such as spleen, kidney, bone, etc. are mainly characterized by compression symptoms caused by space-occupying cysts, almost all accompanied by symptoms of liver or pulmonary hydatid disease.

Examination of echinococcosis

1. Blood: Most white blood cell counts are normal, and eosinophils are slightly elevated.

2. Immunological examination:

(1) Intradermal test (Casonis test): intradermal injection of human or amniotic fluid cyst 0.1-0.2 ml, local papules increased significantly after 15 min, surrounded by redness, pseudopods may appear (immediate reaction); 12 ~ After 24 hours, subcutaneous redness and induration (delayed reaction), the test is simple and rapid, but there may be false negative and false positive reaction, the positive rate is 70% to 95%, and tuberculosis, cysticercosis and paragonimiasis may have Cross reaction.

(2) Serum immunological tests: including agar diffusion, convective immunoelectrophoresis, indirect hemagglutination and enzyme-linked immunosorbent assay (ELISA), enzyme-linked immunoelectro-transfer bolt (EITB), etc. The sensitivity and specificity of EITB are high, and patients with low serum antibody levels can be detected. The positive rate of various serum immunological tests is higher than that of liver hydatid; the rupture of hydatid sac is more complete. High; multiple echinococcal sac patients are higher than individual, but may cross-react with cysticercosis.

(3) Determination of circulating antigen: The detection of circulating antigen has important diagnostic value, but it has the disadvantages of low sensitivity and poor specificity. The application of monoclonal antibody can improve its sensitivity and specificity, often using double antibody sandwich. ELISA.

3. Ultrasound examination: B-mode ultrasound examination has the advantages of simple, rapid and no damage. It can be seen that the round cyst of the liver is clear and round, and the location, size and number can be determined. Sometimes the sac and the sac in the sac are visible. point.

4. X-ray examination: X-ray films of patients with pulmonary hydatid cysts can be seen in different sizes, isolated or multiple round or oval, with clear edges and homogeneous shadows.

5. CT imaging examination: liver and lung granulocytic echinococcosis showed a smooth and uniform cystic shadow on the edge, accurate positioning of the hydatid cyst, size measurement and counting are reliable.

6. MRI examination: The echinococcal lesion showed a uniform low signal on the T1-weighted image, a high signal on the T2-weighted image, and a low signal on the proton density image, and some showed equal signals in the cystic echinococcosis. Diagnostics, there is no more superiority than CT.

Diagnosis and identification of echinococcosis

In the epidemic area, there is a close contact with the dog. The positive test of the worm and the serum immunological test suggest that there is a hydatid infection. The liver B-ultrasound and CT scan have found cysts to help diagnose, but need to be non-parasitic. Cysts such as congenital hepatic cysts, hepatic hemangioma, etc., lung hydatid cysts break into the bronchial tubes, patients cough up powdery skin-like substances, microscopically found powdery membrane-like, head or small hook to determine the diagnosis.

It needs to be differentiated from non-parasitic cysts such as congenital hepatic cysts and hepatic hemangioma.

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