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1、TrematodeTrematode（吸虫）（吸虫） IntroductionnTaxonomic position Phylum platyhelminthes Class Trematoda Order Digenea SpeciesSpeciesReside inReside in Clonorchis sinensis hepatic bile duct Fasciolopsis buski Small intestine Paragonimus westermani Lung, subcutaneous, etc. Schistosoma japonicum S.mansoni, e
2、tc portal systemTrematodes that have medical importanceGeneral featuresz Leaf-like flattened bodies with no body cavity; with oral and ventral suckers to aid attachment to their hostsnThe tegument is a syncytial layer equipped with spines and musclesnDigestive system degenerated，with a mouth, enclos
3、ed by the oral sucker but no anus. mouthpharynx esophagus two digestive tracts nHermaphrodite or monoecious except blood flukes (dimorphism) , possessing both male and female reproductive organs, the appearance and position of which are very important taxonomicallyGeneral featuresReproductive system
4、 of trematodeFemale: ovary, oviduct, ootype, Mehlis gland, seminal receptacle, Laurers canal, vitellaria, vitelline duct, & uterusMale: testis, vas efferens, seminal vesicale, cirrus,&cirrus pouchnLife cycle is complicated indirect life cyclenUsually need one or two intermediate host bio-helmithsbio
5、-helmithsnThe first intermediate hosts are usually fresh water snailsGeneral featuresnEggs can only develop (hatch) in the fresh water n Asexual phase:Eggsmiracidium in watersporocyst in snail redia cercaria release in water encysted metacercaria in second intermediate host infective stagenSexual ph
6、asePreadult (Juvenile)migrated to favorable residing site adult worm lay eggsGeneral featurescercariametacercariarediasporocystmiracidiumeggnEncysted metacercaria is usually the infective stage (Schistosoma- cercaria)nEgg has operculum except blood flukenFeatures reflecting adaptation to parasitismO
7、rgans of attachment developedRetardation of digestive systemHighly developed reproductive systemGeneral features Clonorchis sinensis 华支睾吸虫 (liver fluke,肝吸虫肝吸虫)Introductionnfound from the biliary passage of a Chinese in Calcutta, India in 1874 firstly. nClonorchis sinensis is known as the oriental or
8、 Chinese liver fluke because it is distributed throughout Japan, Korea, China and Vietnamn It is estimated that there are more than 30,000,000 humans getting infection in these areas nIt is a food-borne pathogen, causes clonorchiasisnThe parasite also infects a number of other animals, including dog
9、s, cats, pigs, and rodents, and these animals serve as reservoirs of infection - zoonosis MorphologynAdult: 1- 2.5 cm, flat, size and shape like the seed of sunflower nWith oral sucker and ventral suckernThe two testes of the male productive organ are branchedYounger worm Sucker & spineoral suckerph
10、arynxcecaventral suckervitellariaSeminal receptacleuterusovaryTestis Excretory bladderdigestive tractEggsnAverage 2917m, yellow brownnThe smallest helminth eggnLight bulb shape which also looks like sesame or water melon seeds nOperculum with distinctive shoulders nSpine or knob on posterior endnCon
11、tains miracidium when discharged n operculumn shouldersn spine/knobn well-developed miracidiumcercariametacercaria Life cyclenNeed two intermediate hosts1st intermediate host: fresh water snails, miracidium developed to cercaria in intestine2nd intermediate host: fresh water fishes or shrimps, cerca
12、ria to metacercaria in musclesnInfective stage: metacercaria Infective route: oral consumption of infective stagenDefinitive host: human beingnReservoir host: dogs, cats - zoonosisLodging site: hepatic bile duct Life cycle1st intermediate host: fresh water snailsParafossarulus striatulusAlocinma lon
13、gicornisBithynia fuchsianus2nd intermediate host: fresh water fishes and shrimpsnMinnows or carps Pseudorasbora parvaPathogenesis nStage responsible for the pathogenesis: adult wormMechanical irritation suckersToxic effects excretions, secretions, metabolitesBiological interference nutrition depriva
14、tion nInvasion of biliary epithelium inflammation cell infiltration and proliferation thickening of the duct wall occlusion extensive involvement fibrosis of the liver hepatocirrhosisPathogenesisAdult worm in hepatic bile ductrabbit infected with Clonorchis sinensis shows fibrosis of the bile ductra
15、bbit infected with Clonorchis sinensis shows hepatocirrhosishepatocirrhosisClinical featuresnAsymptomatic to heavy bile duct diseasesHepatomegaly, jaundice, pancreatitis, bile duct stones, biliary cancernMaximum worm burden report 70,000 wormsnIn child, symptoms are usually more serious, could also
16、show malnutrition, nanoid, anemia and sometimes causes deathEnlargement of liver and spleenClonorchiasis patientsClinical featuresClonorchiasis patientsHepatocirrhosis with ascites nanoid kid Clinical featuresDiagnosis nHistory of eating raw fish or shrimpsnEtiological examsKato-Katz methodSedimenta
17、tion method is the choice for fecal or duodenal aspiration examination if egg burden is low nImmunological diagnosisELISA for specific antibodies or circulating antigensEpidemiology and control nDistributed in the Far East including China, Korea, Japan, Vietnam and far east part of RussianIn china,
18、it covers 25 provinces with the highest prevalence in Guangdong (5,000,000 cases), totally 10,000,000 reported cases over the country in year 2003 survey nDietary habit is the hard part for the disease controlnFactors associated with endemic:Existence patients and reservoir hosts (cats & dogs)Presen
19、ce of first & second intermediate hosts in the same water bodyMode of fish breedingDining habit and customEpidemiology and controlnControl measurements:Hygiene education avoid eating raw or undercooked freshwater fishes; separate the raw and cooked food preparation area Protect fish pond from being contaminated by the feces Control of reservoir hosts pets at home, no raw fresh-water fish for catsCure patients and carriers Praziquantel (drug of first choice), 25mg/kg，tid3dEpidemiology and control