刚地弓形虫
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第二章原虫第六节刚地弓形虫属于孢子纲,真球虫目,弓形科。
是由一法国学者首先在刚地梳趾鼠单核细胞内发现,虫体呈弓形,故而得名。
引起的疾病称弓形虫病,人和动物均可感染,是人兽共患病。
一.形态弓形虫发育全过程有5个不同形态阶段:滋养体、包囊、裂殖体、配子体、卵囊①~②阶段寄生在中间宿主(人和各种动物)的有核细胞内;③~⑤阶段寄生在终宿主(猫科动物小肠上皮细胞内)1.滋养体:在中间宿主有核细胞内发育的阶段,因繁殖速度快,又称速殖子。
弓形。
被寄生的细胞内以二分裂法、二芽殖法、裂体法繁殖。
当多个速殖子聚合在细胞内时形成所谓的假包囊。
速殖子繁殖多时,即可挤破细胞,有时可进入血流,侵犯其他组织细胞。
2.包囊:仍是在中间宿主细胞内形成,是在机体免疫功能正常时,速殖子繁殖速度减慢,形成包囊。
形态:圆形或椭圆形;外有一层具弹性坚韧的囊壁包住,内含数个至数百个滋养体,包囊内滋养体也称缓殖子。
包囊在一定条件下也可破裂,缓殖子重新侵患新细胞。
3.裂殖体:在猫科动物小肠绒毛细胞内发育增殖而形成。
形态:长椭圆形,裂殖子形如新月,4.配子体:在小肠上皮细胞内,裂殖体破裂,裂殖子侵犯新的上皮细胞,又形成新的裂殖体5.卵囊:见于猫粪便中。
形态:圆形或椭圆形,直径10~12μm。
囊壁:光滑、透明,两层。
内含物:为二个孢子囊,每个孢子囊含4个子孢子。
未成熟的卵囊仅见一个孢子囊,约10天左右发育到成熟卵囊。
成熟卵囊也有内含4个孢子囊的。
二.生活史1.生活史过程需要二个宿主:终末宿主:猫科动物——①有性生殖阶段;②无性生殖也进行——即裂体增殖。
中间宿主:非常广泛。
哺乳类(包括人、猫均可)、爬行类、两栖类、鸟类2.人体的感染:感染阶段:①成熟卵囊(子孢子);②假包囊(速殖子);③包囊(缓殖子)。
均有一定的抵抗力,尤以包囊、卵囊具囊壁更强。
感染途径:①食入污染了卵囊的食物②食入含有包囊或假包囊的未煮熟的各种动物的内脏、奶制品、蛋类等③先天性感染:母体通过胎盘传给胎儿,即血中束殖子可进入血液中传播。
刚地弓形虫 Toxoplasma gondiiIntroduction1.Toxoplasma gondii 是猫科动物的肠道球虫,因其滋养体形似弓形而得名。
2.其分类地位是:Kingdom Protista>Subkingdom Protozoa>PhylumApicomplexa>Class Sporozoa>Order ?>Family Toxoplasmatidae> Toxoplasma gondii3.该虫呈世界性分布,可感染鸟类、鱼类、哺乳动物和人,引起Toxoplasmosis.人群平均感染率33%,有5亿人抗体阳性。
我室血清学检查数据显示重庆地区孕妇抗体阳性率20%以上。
4.Morpholog y Trophozoite (tachyzoites and bradyzoites)Indirect fluorescent antibody test. Slide shows endozoites exposed to antibody containing serum and then treated with fluorescein conjugated anti-human globulin. There is a zone of light green fluorescence around each organism. The cytoplasm appears reddish as it was counterstained with Evan's blue. ×1000. Enlarged by 5.4.In the centre is a macrophage filled with endozoites. This stage is also known as the pseudocyst. Giemsa stain. ×1000. Enlarged by 9.6.A ruptured macrophage which has liberated endozoites. Many are still lying close to the macrophage nucleus. Giemsa stain. ×1000. Enlarged by 9.6.A ruptured macrophage with the endozoites dispersed in the background. Some parasites are undergoing division. The large dense body is the macrophage nucleus. Giemsa stain. ×1000. Enlarged by 5.4.A macrophage containing endozoites and some free endozoites, stained with acridine orange. The cytoplasm of the endozoites consisting mostly of RNA takes up a red color and the nucleus consisting mainly of DNA takes up a yellowish green color. ×1000. Enlarged by 5.4.Intracellular tachyzoites of Toxoplasma gondii.Freshly passed Toxoplasma oocysts. Most of the oocysts have a single spororblast. Interference contrast. ×400. Enlarged by 5.4.Toxoplasma oocysts after incubation in vitro for 12 hours.Most of the oocysts have now sporulated. Interference contrast. ×400. Enlarged by 23.4.Toxoplasma cyst from mouse brain. The cyst has partly detached from the brain tissue. Phase contrast. ×400. Enlarged by 5.4.Toxoplasma cyst from mouse brain.The cyst has completely detached from the brain tissue. Phase contrast. ×400. Enlarged by 5.4.Toxoplasma cyst from mouse brain.Showing the argyllophilic nature of the cyst wall after silver staining. This is the best method for demonstration the cyst wall. ×1000. Enlarged 5.4.Toxoplasma cyst from mouse brain. Showing the PAS positive cystozoites. The cyst wall is faintly visible. This is the best method for demonstrating the cystozoites. ×1000. Enlarged by 5.4.Toxoplasma cyst from mouse brain after H and e stain.The cyst wall is faintly visible and the nuclei appear as dark bodies inside the cyst. ×1000. Enlarged by 5.4. Life Cycle在中间宿主体内的发育1 Infective stage:(1) Oocyst in feces of cat(2) cyst or pseudocyst in muscle of animals.2 感染方式和途径经口感染。
刚地弓形虫检验及临床意义
一、正常值
刚地弓形虫寄生于细胞内,且无组织器官选择性,病原检查较为困难,直接涂片法阳性率较低。
多采用免疫学方法进行血清学检查。
正常人血清抗弓形虫抗体(IgG类、IgM类)为阴性。
二、影响因素
1、试剂从冰箱取出后应恢复至室温(18~25℃)。
2、不同厂家、批号的试剂不可混用。
3、标本应避免溶血、脂血。
三、临床意义
1、弓形虫感染是一种人畜共患病,由猫与其他宠物感染人的可能性较大。
后天感染轻型者常无症状,但血清中可查到抗体;重型者可有各种症状,如高热、肌肉和关节疼痛、淋巴结肿大等。
2、通过胎盘宫内感染可导致流产、早产、死胎和各种异常,患儿出生后可表现一系列中枢神经系统症状以及眼及内脏的先天损害。
3、由于弓形虫在人体细胞内可长期存在,故检测抗体一般难以区别现症感染或以往感染,可根据抗体滴度的高低以及其动力学变化加以判断。
血清抗弓形虫IgM抗体阳性提示近期感染。
血清抗弓形虫IgG抗体阳性提示既往感染。
如在新生儿体内检测到血清抗弓形虫IgM抗体,则表示其有先天的弓形虫感染。