人体寄生虫学第二节 锥虫

1、锥虫 Trypanosome According to the geographic distribution & characteristic pathogenicity, members of trypanosomes that infect humans can be divided into two major groups. One group are African trypanosomes, which include Trypanosoma rhodesiense and Trypanosoma gambiense, the other group is American tr

2、ypanosome namely Trypanosoma cruzi 非洲锥虫病非洲睡眠病 (African sleeping sickness) 由布氏冈比亚锥虫和布氏罗得西亚锥虫引起，由舌蝇传播。1Morphology & life cycleTow distinct forms-the trypomastigote(锥鞭毛体) in the bloodstreamthe trypomastigotes exhibit three forms slender formlong, an undulating member, a free flagellum stumpy formshort,

3、 lacking flagelluma form intermediate between both-the epimastigote(上鞭毛体)-with a large nucleus, a kinetoplast, an undulating member, a free flagellum2345 舌蝇 舌蝇粗短型锥鞭毛体 上鞭毛体 循环后期锥鞭毛体 细长型鞭毛体 中间型鞭毛体粗短型鞭毛体对舌蝇具感染性细长型鞭毛体以二分裂法增殖，而粗短型则不增殖循环后期锥鞭毛体是感染期6Human beings become infected with Trypanosoma rhodesiense

4、or T.gambiense follwing the infection of metacyclic trypomastigotes(循环后期锥鞭毛体)the tsetse fly during the blood mealOnce introduced into the bloodstream, trypomastigotes spread & multiply rapidly, migrate to the cerebrospinal fluid (CSF)Tsetse fly get infected when it ingested stumpy trypomastigotes du

5、ring its blood mealThe stumpy trypomastigotes elongate, multiply, converting into epimastigote (上鞭毛体), then transform into metacyclic trypomastigotes, which are infective stage for human beings78PathogenicityEarly stage (初发反应期): inflammatory reaction called trypanoosomal chancer occurs at the site o

6、f the bitereddening in the skin, a swelling 15 cm in diameter, enlargement of adjacent lymph nodesHemolymphatic stage (血淋巴期): the blood & lymph are invaded,headache, irregular fever develop, enlargement of lymph nodes -in the neck & supraclavicular area Winterbottoms sign罗得西亚布氏锥虫病呈现急性经过，致死亡前病程很少超过一年

7、，有的患者在中枢神经系统未受侵犯之前即已死亡910Central nervous system stage (脑膜脑炎期): final stage of disease mental retardation, tremors, meningoencephalitis the patient slips into coma and death1112症状和体征症状出现率（%）头痛78.7失眠/嗜睡74.4淋巴结肿大56.1感觉过敏51.1脾肿大42.5无力34.8肝肿大25.5营养不良25.2行为异常24.7食欲下降22.9行走困难21.7震颤21.0发热16.1语言困难13.4异常动作10.

8、513Epidemiology T. gambiense is found in tropical West Africa & Central AfricaT. rhodesiense is found in East & Central Africa主要由舌蝇传播 移植、输血、注射事故也可传播Blood transfusion, transplant are additional routes of transmission The antelope (羚羊) may serve as reservoir host保虫宿主:羚羊14DiagnosisMultistep procedure:

9、clinical assessment examination of blood smearsbone marrow, or CSF for trypomastigotes antibody detectionIFA.ELISATreatment Suramin 早期疗效100% Eflornithine（依弗鸟氨酸）早晚期会更有效Suramin is effective against African sleeping sickness when treatment is initiated early in the course of the disease, Eflornithine w

10、ill be more effective one15由 Trypanosoma cruzi引起美洲锥虫病 Chagas disease,Trypanosoma cruzi is responsible for Chagasdisease由锥蝽 (reduviid bug vector)传播。Trypanosoma cruzi16Morphology & life cycleamastigote: a nucleus, a kinetoplast, a blepharoplast, an axonemetrypomastigote: similar to that of African try

11、panosomesT. cruzi is most frequently transferred to a human host when a reduviid bug vector (锥蝽)defecates infective metacyclic trypomastigotes near the site of its blood meal17After entry into host, trypomastigotes invade surrounding cell & transform into amastigotes, which are multiply, destroy the

12、 host cells, convert back into trypomastigotes 非复制型的血流内的锥鞭毛体The resulting trypomastigotes migrate into the blood, and penetrate additional cells in the body, transform back into amastigotes, the replication & destruction cycle repeat-heart muscle, liver & brain will become infected 复制型的细胞内的无鞭毛体The t

13、rypomastigotes are transmitted back to the reduviid bug via a blood meal 循环后期锥鞭毛体随锥蝽粪便排出于哺乳动物体表18 锥鞭毛体 无鞭毛体 球鞭毛体 上鞭毛体 循环后期锥鞭毛体 上鞭毛体 无鞭毛体The matacyclic trypomastigotes are then passed with the feces when the bug defecates near the site of its next blood meal, the cycle begins again锥蝽吸血锥蝽粪便污染 后位传播或污染传

14、播，有别于非洲锥虫病的前位传播或接种传播19夜间吸血粪便中虫体经伤口侵入先天感染输血传播.2021Disease is named after Carlos Chagas, a Brazilian who discovered T. cruzi in conenosed bugs in 1910. 22Pathogenicity：人体所有有核细胞均是潜在的感染靶细胞 the parasite invade macrophage of the subcutaneous tissue at the site of infection, causing a local, edematous swel

15、ling called a chagoma, kiss bugs ( about 1-3 weeks after infection, fever, headaches, malaise, and prostration may develop)急性期 Chagoma、kiss bugs,伴发热、头痛等，也可肝脾肿大23Thatched roof hutEye infection (Romanas sign)2425In chronic stage: myocarditis, enlargement of colon and esophagus, hepatosplenomegaly 慢性期

16、急性后10-20y，心肌炎、巨食道、巨结肠Histologic section of heart muscle infected with T. cruzi amastigotes. 2627enlargement of colon28Normal heartChagas heartNormal intestineChagas intestineChagas Disease - Chronic Stage: 10-40 years after infection 20-30% of infected people develop serious symptoms Enlarged heart

17、Enlarged esophagus or bowel29克氏锥虫临床病程及症状30EpidemiologyT.cruci is found in South and Central America, rarely in North America主要经锥蝽传播 移植、输血、胎盘或被锥蝽粪便污染的食物也可传播，保虫宿主犰狳。The highest prevalence of disease is in BrazilAdditional routes of T.cruci transmission include blood transfusion,transplacental, and ent

18、ry through the mucous membranes when the bug bite occurs near the eye or month3132Diagnosis Giemsa-stained blood slides lymph node biopsy giemsa-stained slides culture of bloodNNN mediumamastigotes serologic testsIFA, ELISA xenodiagnosis PCRTreatmentThe treatment of choice for infection with T.cruci is Nifurtimox（硝基呋喃类）333435Diagnosis Giemsa-stained blood slides lymph node biopsy giemsa-stained slides culture of b