How to prevent schistosomiasis

      1、 Basic knowledge of schistosomiasis

　　(1) Life history

　　Schistosoma japonicum is a parasite that lives in human and mammalian bodies.

　　The name comes from the fact that adults live in the blood vessels of their hosts.

　　Schistosomiasis is commonly known as "abdominal disease". In fact, it refers to advanced schistosomiasis, which is characterized by splenomegaly, hypersplenism, portal hypertension, varicose veins and ascites in the lower part of the esophagus and fundus of the stomach.

　　The life cycle characteristics of schistosoma include sexual reproduction in the host and other mammals and animals and asexual reproduction in the intermediate host freshwater snails. The process can be divided into seven stages: adult worm, egg, caterpillar, mother cyst, daughter cyst, cercaria and child worm.

　　When the final host and mammals contact the water body containing schistosoma cercariae, the cercariae invade the final host through skin tissue, continue to develop into a child worm, and migrate through the lung to the portal mesenteric vein to live, gradually develop into an adult worm and mate and lay eggs. The eggs are discharged from the final host in time with feces to infect the intermediate host snails in vitro, forming a new cycle.

　　Oncomelania is the only intermediate host of Schistosoma japonicum, its size generally does not exceed 1cm (snails with a length of more than 1cm are generally not snails), and its width does not exceed 4mm.

　　(2) Route of infection

　　Schistosoma japonicum infects the body in the invasive way of cercariae.

　　The cercariae float in the water.

　　Once people or mammals come into contact with water, floating cercariae will stick to the skin surface when the skin water is not dry or will be dry.

　　The results showed that the shortest time for cercariae to invade humans was 10 seconds.

　　Schistosoma can infect all year round.

　　The infection rate in China is mainly from March to November, with the highest rate from April to May in summer and from July to September in autumn.

　　The main route of schistosomiasis infection in humans is skin infection, followed by oral mucosa infection.

　　Affected by production (breeding in epidemic areas, transplanting seedlings, fishing, shrimp fishing, fishing, grass cutting, water grass cutting, rice dumplings, working in flood control and drainage areas) and daily life (such as rivers, ditches, lakes in epidemic areas).

　　Infection caused by contact with schistosomiasis water, such as washing rice, vegetables, hands and feet, drinking raw water, etc.

　　(3) Symptoms and signs of acute schistosomiasis

　　Acute schistosomiasis is caused by acute fever, hepatosplenomegaly, diarrhea, cough and other clinical features (Figure 3).

　　According to clinical manifestations, it can be divided into mild, moderate and severe.

　　All patients with acute schistosomiasis have a clear history of exposure to epidemic water.

　　It generally occurs at the turn of spring, summer and summer and autumn, with the peak occurring in June to October.

　　The main ways of infection are swimming, fishing and shrimp catching, lake grass hunting, summer grain grabbing, flood control, etc.

　　Therefore, special emphasis is placed on asking for medical history.

　　2、 Personal protection knowledge of schistosomiasis in flood season

　　In schistosomiasis endemic areas, the best way to prevent schistosomiasis is not to contact the water in the endemic area.

　　1. Residents in epidemic areas and personnel involved in flood fighting and disaster relief should try to avoid contact with infected water, and try to shorten the contact time, contact times and contact area.

　　2. When it is necessary to contact with polluted water, personal protective measures shall be taken as far as possible.

　　At present, rubber boots, nylon protective pants and rubber gloves are commonly used for protection.

　　It is better to use clothes, gloves, socks and leggings soaked in 1% niclosamide.

　　3. Use protective drugs to prevent infection.

　　In case of unavoidable contact with infected water, apply protective oil (anti cercaria cream) to the places that need to contact with infected water before contact.

　　4. Do not directly affect the drinking of epidemic water, do not play in the epidemic water, swim and wash equipment and appliances. The drinking water must be disinfected or boiled to ensure the safety of drinking water.

　　5.1 In case of contact with water, red itchy papules or cough, chest pain and other symptoms within 2 weeks, as well as fever, chills, abdominal distension, abdominal pain, diarrhea, hepatomegaly, liver pain and other symptoms in about one month, the nearest schistosomiasis prevention and control institution or disease center should be visited as soon as possible for disease control, so as to timely find, diagnose and treat.

　　6. In order to prevent the outbreak of acute schistosomiasis, people exposed to water should use artesunate or artemether for prevention as soon as possible after the first contact, or use praziquantel as a preventive treatment after 4 weeks.

　　7. If you have been in contact with infected water for many times, especially when participating in disaster relief, you should go to the schistosomiasis prevention and control institution for special inspection of schistosomiasis within one month. If you find positive, you need to give timely treatment to the pathogen.

　　3、 Key technical points of schistosomiasis control in flood season

　　1. Early warning

　　Grasp the flood situation, carry out special research on disease prevention and risk analysis, and prepare personnel and materials for sudden epidemic.

　　2. Risk reduction

　　During the flood season, the slow release method of niclosamide was used to kill cercariae in the water body of the susceptible zone.

　　After the disaster, careful planning, full preparation and comprehensive investigation shall be carried out for the area of flooded snails and the areas where they may spread. For key and suspicious snails, niclosamide shall be used to kill snails and larvae.

　　3. Robust education

　　Through health education, the awareness of schistosomiasis prevention among the people in disaster areas and disaster relief personnel will be improved, and the people will be advised to avoid contact with epidemic water as much as possible.

　　Necessary protective measures shall be taken for the personnel who must contact the epidemic water in flood fighting and self rescue.

　　4. Focus

　　The officers and soldiers, cadres and residents participating in flood control and rescue, local residents who rush to harvest and rush to plant, fishermen and migrant workers from other places should pay special attention, make a good record and issue prevention supplies, and track and observe these people.

　　5. Catch the sentry point

　　Medical institutions (sentinel hospitals) in epidemic areas implement the first diagnosis system for fever patients, and carry out schistosomiasis surveillance and registration follow-up for water related personnel.

　　6. Housekeeping

　　Actively communicate with agricultural and livestock departments, and take advantage of favorable opportunities to carry out universal treatment of schistosomiasis in domestic animals; We will strengthen livestock management and strictly implement measures such as banning grazing on the mainland.

　　7. Safe water

　　Residents are required to take water in the designated safe living area.

　　If the drinking water source may contain schistosoma cercariae, it shall be sanitized before drinking.

　　The method is: add 0.5 g of bleach or 1 g of bleach powder every 50 kg of water, and drink it after 30 minutes.

　　8. Fecal management

　　Build temporary toilets to educate people not to defecate anywhere.

　　Egg killing treatment shall be carried out for human and livestock feces by mixing 50 kg feces with 250 g urea and storing them for more than 1 day.

　　9. Monitoring

　　It is necessary to strengthen the management of fever clinics. For patients with fever, especially those in schistosomiasis endemic areas, it is also necessary to check whether they are infected with schistosomiasis after screening for new coronavirus infection. For schistosomiasis cases, early detection, early reporting, early diagnosis and early treatment should be achieved in a timely manner.

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