刚地弓形虫

简称弓形虫，弓浆虫。寄生于人和许多种动物的有核细胞，引起人畜共患的弓形虫病(toxoplasmosis)。特别在宿主免疫功能低下时致病，属机会致病原虫(opportunisticprotozoa)刚地弓形虫（Toxoplasmagondii）一、形态在发育过程中，有5种形态。滋养体在有核细胞内，假包囊内滋养体叫速殖子tachyzoite包囊cyst大量虫体分泌物形成的囊状结构，包囊内滋养体叫缓殖子bradyzoite卵囊oocyst内含2个孢子囊，每个孢子囊内含4个子孢子。裂殖体配子体Toxoplasmagondiiinthebronchoalveolarlavage(BAL)materialfromanHIVinfectedpatient.Numeroustrophozoites(tachyzoites)canbeseen,whicharetypicallycrescentshapedwithaprominent,centrallyplacednucleus.Mostofthetachyzoitesarefree,somearestillassociatedwithbronchopulmonarycells.microscopicalfeaturesoftachizoitesofToxoplasmagondiiandperitonealmacrophagesofmouseinperitonealexudate.(SEM)microscopicalfeaturesoftachizoitesofToxoplasmagondiiandperitonealmacrophagesofmouseinperitonealexudate.(SEM)T.gondii:transmisionelectronmicroscopicpicture.Longitudinalsectionofanendozoid.T.gondii:cross-sectionthroughanendozoidinanadvancedstageofendodiogeny.Thedaugthercellsappeartobesurrounded.Ineachofthesenewscellstherearetworoundbodiesthatlengthenformingthefirstrhoptries.Toxoplasmagondiiintissuefromacat.toxoplasmicpseudocystwithinaninflammatorytissuereaction.(H&Estain).thepseudocystsofT.gondiicanbeobservedintissuesectionswithmonoclonalantibodies.incellculturesT.gondiiproliferatestoformapseudocystof8-20parasites.(TrophozoitesinaTHP-1cell,Giemsastain).二、生活史肠上皮细胞裂体增殖裂殖体—裂殖子肠上皮细胞配子生殖♀♂配子—合子—卵囊有核细胞内内二芽/二分裂滋养体有核细胞外包囊卵囊——子孢子终末宿主：猫科动物中间宿主：极广泛，包括人及猫随猫粪排出免疫力滋养体—速殖子包囊——缓殖子寄生部位：所有有核细胞宿主：广泛感染阶段：卵囊，滋养体（速殖子、假包囊），包囊感染方式：1）后天感染a)误食被卵囊污染的食物。b)生吃肉类、乳类c)通过器官移植、输血等医疗手段2）先天感染孕早期感染弓形虫，通过胎盘传给胎儿三、致病人对弓形虫普遍易感，免疫功能正常时常处于隐性感染状态，当宿主免疫功能低下时异常增殖而致病。速殖子是主要致病阶段。虫体侵入有核细胞大量增殖，组织细胞被破坏，炎症细胞侵润，导致组织的炎症、坏死。虫株毒力RH株（强毒株）可使宿主迅速死亡Beverley株（弱毒株）增殖缓慢，易形成包囊危害因素弓形虫毒素(toxotoxin)一种抗原，致死因子，可致小鼠惊厥、后肢麻痹，几分钟后死亡。弓形虫素(Toxoplasmin)对鸡胚胎有致畸作用。弓形虫因子(Toxofactor)培养的上清液提取物，可阻止母鼠受孕，或流产，或胚胎发育停滞。临床分型：1、先天性弓形虫病孕早期弓形虫通过胎盘传给胎儿,可造成流产，早产，畸胎或死产。2、获得性弓形虫病因侵犯部位和机体反应性不同临床表现。常见的是发热（中、长程热），淋巴结肿大（颌下、颈后），神经系统的炎症（脑炎、脑膜炎），眼部炎症（视网膜脉络膜炎）。弓形虫脑病眼弓形虫病CTscanofatoxoplasmicencephalitis.Thetypicallesionisanipodensefocalareawithringcontrast-enhancementandedema.四、实验诊断1、病原学诊断（1）体液涂片染色法（2）动物接种和细胞培养法2、血清学诊断（1）IHA、IFA、ELISA查抗原或抗体（2）PCR及DNA探针技术可早期诊断T.gondii:directdetectionofT.gondiiinclinicalspecimens五、流行本病是人兽共患寄生虫病，人群抗体阳性率25-50%。许多与人关系密切的动物感染率亦高，是重要传染源。流行因素：1、传染源猫科动物、其他哺乳动物、感染者2、传播途径胎盘；食入、伤口接触、输血等3、易感人群普通人，胎儿、肿瘤和AIDS患者更易感广泛流行的原因1、多个生活史阶段均有感染性。2、中间宿主极广泛。3、可在终宿主间、中间宿主间、终宿主与中间宿主间互相感染。4、包囊可在中间宿主组织内长期存在。5、卵囊排放量大，抵抗力强。六、防治对本病重在预防。1、急性期患者常用乙胺嘧啶、磺胺类和增效剂联合用药。疗程中可配用免疫增强剂。2、加强对家禽、家畜和可疑动物的监测。3、加强肉类检疫和食品卫生管理。4、定期对孕妇作弓形虫常规检查。其他机会致病原虫•肺孢子虫寄生肺泡上皮细胞，引起间质性肺炎。•隐孢子虫寄生肠粘膜，引起腹泻。•等孢球虫寄生小肠上皮细胞内，引起腹泻。•圆孢子虫寄生肠粘膜，引起腹泻。[LastModified:11/20/200016:53:26][Pneumocystisjiroveci(syn.Pneumocystiscarinii)]Pneumocystisjirovecicysts.A:3cystsinbronchoalveolarmaterial,Giemsastain;theroundedcysts(size4to7µm)contain6to8intracysticbodies,whosenucleiarestainedbyGiemsa;thewallsofthecystsarenotstained;notethepresenceofseveralsmaller,isolatedtrophozoites.B:cystsinlungtissue,silverstain;thewallsofthecystsarestainedblack;theintracysticbodiesarenotvisiblewiththisstain;babywhodiedwithpneumoniainCalifornia.AB[LastModified:11/20/200016:53:26][Pneumocystisjiroveci(syn.Pneumocystiscarinii)]Pneumocystisjirovecicysts.A:3cystsinbronchoalveolarmaterial,Giemsastain;theroundedcysts(size4to7µm)contain6to8intracysticbodies,whosenucleiarestainedbyGiemsa;thewallsofthecystsarenotstained;notethepresenceofseveralsmaller,isolatedtrophozoites.B:cystsinlungtissue,silverstain;thewallsofthecystsarestainedblack;theintracysticbodiesarenotvisiblewiththisstain;babywhodiedwithpneumoniainCalifornia.ABA:3cystsinbronchoalveolarmaterial,Giemsastain;theroundedcysts(size4to7µm)contain6to8intracysticbodies,whosenucleiarestainedbyGiemsa;thewallsofthecystsarenotstained;notethepresenceofseveralsmaller,isolatedtrophozoites.B:cystsinlungtissue,silverstain;thewallsofthecystsarestainedblack;theintracysticbodiesarenotvisiblewiththisstain;babywhodiedwithpneumoniainCalifornia.Pneumocystisjirovecitrophozoitesinbronchoalveolarlavage(BAL)material;Giemsastain.Thetrophozoitearesmall(size:1to5µm),andonlytheirnuclei,stainedpurple,arevisible(arrows).AIDSpatientseeninAtlanta,Georgia.IndirectimmunofluorescenceusingmonoclonalantibodiesagainstPneumocystisjiroveci.SpecimenfromapatientwithAIDS,seeninGeorgia.•LaneS:Molecularbasepairstandard(100-bpladder).Blackarrowsshowthesizeofstandardbands.•Lane1:SinglestepPCRamplificationwiththepAZ102-E/pAZ102-Hprimerpair1-diagnosticbandsize:346bp.•Lane2:NestedPCRamplificationwiththeITSnestedPCRprimers,1724F/ITS2R(firstround)andITS1F/ITS2R1(secondround)2-diagnosticbandsize:550bp.MolecularDiagnosisA:Agarosegel(2%)analysisofPCR-amplifiedproductsfromDNAextractedfromabronchoalveolarlavage(BAL)diagnosticspecimenofapatientwithpulmonarysymptoms.OocystsofIsosporabellicanalsobestainedwithacid-faststain,andcanbevisualizedbyepifluorescenceonwetmounts,asillustrated.Threecoccidianparasitesthatmostcommonlyinfecthumans,seeninacid-faststainedsmears(A,C,andF),bright-fielddifferentialinterferencecontrast(B,D,andG)andepifluorescence(EandH,C.parvumoocystsdonotautofluoresce).A,B,C:Oo