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1、,山东大学 医学院 病原生物学研究所 寄生虫学教研室 郭淑玲,Schistosoma(裂体吸虫 ),They belong to Genus Schistosoma, live in blood vessel and cause schistosomiasis. People call them blood flukes. There are four species infecting human body. They are:1. Schistosoma japonicum（日本血吸虫）is prevalent in Far East. In china, it is prevalent
2、in Yangtze valley and south of Yangtze except Guizhou Province. The adults live in the portal vein system, causing liver cirrhosis（肝硬化）and portal vein hypertension syndrome（门脉高压征候群）.,2. Schistosoma mekongi (湄公血吸虫) is merely distributed in Mekong River Valley（澜沧江：青海，西藏，云南湄公河：老挝，泰国，柬埔寨), resembles Sch
3、itosoma japonicum except intermediate host.3. Schistosoma haematobium（埃及血吸虫）widely spreads in Africa, chiefly in Nile River valley. The adults live in the vesical and pelvic plexus causing painless terminal haemuresis, renal failure complicated by the ureter obstruction. In the endemic area infectio
4、n is so common that haemuresis is accepted as a sign of manhood in young boy.4. Schistosoma mansoni（曼氏血吸虫）is distributed in Africa and focal area in Latin America. Lives in the portal and hemorrhoidal vein plexus, causing stool with fresh blood, liver cirrhosis and portal vein hypertension.,Schistos
5、oma japonicumOnly Schistosoma japonicum is found in China. Schistosomiasis is one of the “five major parasitic diseases”. It is prevalent in 13 provinces, city and autonomic regions (except Guizhou ) along Yangtze River Valley and south of Yangtze where are main areas for producing rice. I. Morpholo
6、gy1. Adult worms are elongated cylindrical in shape, unlike other flukes. Two sexes are separate, gray white in color, but the female is much dark and slender, the male is shorter and thicker, sickle-like. In human body the male usually embraces the female into its gynecophoral canal (抱雌沟), appears
7、“ K ”like (or the female usually resides in males gynecophoral canal).,Male: 10-20 x 0.5-0.55mm in size, oral sucker at top near by ventral sucker. Just behind the ventral sucker there is a longitudinal groove-gyncophoral canal in which the female normally resides. The esophagus is divided into two
8、branches in front of the ventral sucker, and then unite to form a cecum at the posterior third part of the body. Seven testes are situated one by one, each has a delicate efferens which combine to form the vas deferens and dilate to become a seminal vesical opening in the genital pore just behind ve
9、ntral sucker.,Female: Longer and slender than the male, much dark colored thread-like, 12-26x 0.1-0.3mm in size. The digestive system is similar to that of male. The vitellaria are located in the posterior part of the body surrounding the cecum. The unbranched, oval ovary lies in the mid-portion of
10、the body. The uterus lies in the anterior portion of the body filled with 50-300 eggs arranged in a single row, arising from ootype to genital pore behind the ventral sucker.,Male and female schistosomes. (Drawn by Sylvia Treadgold) WHO,Paired male and female adult worms. The female schistosomulum i
11、s the darker, curled worm within the males gynacophoric canal.,2. Mature egg is oval in shape, slight yellow in color, 89 x 67, shell is thin without an operculum but with a lateral spine. The content is a miracidium. Under the electron microscope there are many micro-tubules on the shell, through w
12、hich the soluble egg antigen (SEA) secreted by a miracidium.3. Cercaria is infective stage. It is composed of the body and forked tail (including tail stem and fork) and has 5 pairs of penetrating glands in the body.,oval in shape, slight yellow in color, 89 x 67 shell is thin without an operculum b
13、ut with a lateral spine.,The small spine is generally not visible as the egg surface is often covered with facal debris.,oval in shape, slight yellow in color, 89 x 67 , shell is thin without an operculum but with a lateral spine.,Forked cercaria of S. japonicum,Forked cercaria of S. japonicum,II. L
14、ife cycle,1. Site of inhabitation: the portal vein system, mainly in the inferior mesenteric vein.2. Infective stage: cercaria3. Infective route: by skin4. Intermediate hosts: Oncomelania snail (钉螺)5. Reservoir hosts: mammals such as buffalo, cattle, wild rodents, goat, monkey, pig, fox.6. Eggs are
15、main pathogenic factor: (They are inlaid in the liver and intestinal wall. Some of them are discharged in feces to complete its life cycle).7. The development in human body requires 25-30 days. Cercaria can live 1-3 days. Life span of the adults is about 20-30 years.,*8. Blood fluke is a special kin
16、d of flukes because of following characters: (1) The adult worms look like nematodes, elongated cylindrical in shape.(2) Two sexes are separate.(3) egg without operculum, but with a lateral spine.(4) only one intermediate host required.(5) The infective stage is cercaria. (6) The infective route is by skin.(7) The eggs are main pathogenic stage.,The infective inhabitation of Schistosoma japonicum: mesenteric vein,The intermediate host of S. japonicum: Oncomelania sneil,
