《人体寄生虫学 Human parasitology》课程教学课件（讲稿）Lectures 17 Giardia lamblia

Intestinal FlagellateGiardia lamblia

Giardia lamblia Intestinal Flagellate

IntroductionGiardialamblia:giardiasiszoonosisis one of the major causes of parasiticdiarrhea-"traveler's diarrhea);isthe only commonpathogenicprotozoanfound in the duodenum and jejunum ofhumans,who are the only importantreservoir ofthe infection

Introduction  Giardia lamblia: giardiasis－zoonosis  is one of the major causes of parasitic diarrhea—”traveler’s diarrhea);  is the only common pathogenic protozoan found in the duodenum and jejunum of humans, who are the only important reservoir of the infection

MorphologyGiardia exists in two forms:the trophozoiteandthecystformsTrophozoite9~21μmx5~15μmx2~4μmhalf-pearwithsymmetryfour pairs of flagellaAlargeconcavesuckingdiskontheventral surface helps theorganismto adhereto intestinal villiApairs of nuclei inthesuckingdisk

Morphology  Giardia exists in two forms: the trophozoite and the cyst forms.  Trophozoite:  9～21µmx 5～15µm x 2～4µm  half-pear with symmetry  four pairs of flagella  A large concave sucking disk on the ventral surface helps the organism to adhere to intestinal villi  A pairs of nuclei in the sucking disk

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MorphologyCyst:oviod,thick-walled,highlyresistant, and 8-14 μm in lengththey contain two nuclei asimmatureformsandfour asoO:maturecysts.2

Morphology  Cyst: oviod, thick-walled, highly resistant, and 8–14 µm in length; they contain two nuclei as immature forms and four as mature cysts

Cyst:Giardia irtestinais cystsUnerinnnm-hram-10urn

Cyst:

Life CycleCDCHUMANInfectiveStageINFECTIONThophozoiteandCystwaterCYCLEInfectiousstage:4nucleiCystContamination ofwater,food, orhands/fomites with infective CystsTwotrophozoite in upper.Trophozoitesarealsoregions ofthesmall intestine orpassed in stool buttheydo notsurvive inthe evironiment.duodenumEXTERNALENWIRONMENTExcysts&AstheparasitespassintoDIAGNOSTICDevelopsinFORMSDuodenumthe colon, theytypicallyencyst, and the cysts arepassed inthe stool.BinaryFissionhozotes

 Thophozoite and Cyst  Infectious stage: 4 nuclei Cyst  Two trophozoite in upper regions of the small intestine or duodenum  As the parasites pass into the colon, they typically encyst, and the cysts are passed in the stool. Life Cycle water

Pathogenesis Infections with G.lamblia areoften completely asymptomatic.Symptomatic infection maycause intestinal disorders,most commonly diarrhea.Mechanism is not clear and maybe combined mechanical andchemical factors

 Infections with G.lamblia are often completely asymptomatic.  Symptomatic infection may cause intestinal disorders, most commonly diarrhea.  Mechanism is not clear and may be combined mechanical and chemical factors. Pathogenesis

PathogenesisThemechanical irritationto tissues leads todiarrhea, with increased fat and mucus in the foulsmelling stoolMalabsorptionsyndrome(vitaminAandfats)leadstoweightloss,anorexia,electrolyteimbalanceandabdominalcrampsChildrenandimmunocompromisedindividulas(HiV)aremost significantlyaffected:opportunisticinfection

 The mechanical irritation to tissues leads to diarrhea, with increased fat and mucus in the foul￾smelling stool.  Malabsorption syndrome (vitamin A and fats) leads to weight loss, anorexia, electrolyte imbalance, and abdominal cramps. Children and immunocompromised individulas (HIV) are most significantly affected: opportunistic infection. Pathogenesis

DiagnosisIdentificationof characteristic cysts informedor-partiallyformed stool:concentratemethod iscommonly used to enhance detectionrateasformol-etherconcentrateofastoolpreparationExaminationfortrophozoitesindiarrheicstool福(acutestage),orDuodenalaspiration;Inchronicinfections:serological methods(ELiSA)

 Identification of characteristic cysts in formed or partially formed stool: concentrate method is commonly used to enhance detection rate as formol-ether concentrate of a stool preparation.  Examination for trophozoites in diarrheic stool (acute stage), or Duodenal aspiration;  In chronic infections: serological methods (ELISA). Diagnosis