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Introduction to Protozoa

Introduction to Protozoa. General Account. Unicellular animal with full functions Distribute widely: water,soil, etc. Total species 65,000 Free-living: majority Parasitic: about 10,000. Medical Protozoa. Pathogenic protozoa Opportunistic parasite( 机会致病 ) Not normally pathogens

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Introduction to Protozoa

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  1. Introduction to Protozoa

  2. General Account • Unicellular animal with full functions • Distribute widely: water,soil, etc. • Total species 65,000 • Free-living: majority • Parasitic: about 10,000

  3. Medical Protozoa • Pathogenic protozoa • Opportunistic parasite(机会致病) • Not normally pathogens • Become pathogenic due to impairment of host resistance • Clinical importance of the AIDS epidemic

  4. Basic Structures • Plasma membrane:侵袭致病,免疫反应 • Cytoplasm • Ectoplasm: locomotion , ingestion, etc • Endoplasm: metabolism • Nuclear • Vesicular form(泡状核) or compact form • Locomotive organelle • Pseudopodium(伪足), flagellum(鞭毛), cilia(纤毛)

  5. Mode of Reproduction • Asexual reproduction • Binary fission(二分裂法): results in 2 daughter cells • Schizogony(裂体增殖): multiple fission, results in multiple cells • Endodyogony(内二芽增殖): by internal budding results in 2 cells • Sexual reproduction • Conjugation(接合生殖): exchange of nuclear materials of 2 • Gametogony(配子生殖) : sexually differentiated cells unit  zygote

  6. Life Cycle Patterns • One stage form(简单型) • Trophozoite ( take food, be mobile, multiply) • Two-stage form (简单型) • Trophozoite & cyst (not mobile, with cyst wall) • Two-host form • Mammals – mammals(循环传播型) • Mammals - insect vectors(昆虫传播型)

  7. Characteristics of Protozoan in Infection • Proliferation-parasitemia • No larva and adult differentiation but stage differences • May be intracellular lodgment • Opportunistic & accidental infections (free-living)

  8. Medical Important Species • Amebae • Flagellates • Sporozoites • Ciliates

  9. Pathogenic Intestinal Amoeba Entamoeba histolytica

  10. Morphology • Trophozoite • Size: 10-40 m • Shape: ovoid with pseudopodium • Basic structure: cytoplasm, vesicular nucleus (chromatin granules, nuclear membrane, karyosome)

  11. Cyst • Size: 10-20 m • Structure: cyst wall, 1-4 nuclei, chromatoid body • Physiological function: • The stage of discharge • Resistant to external surroundings • The infective stage

  12. Main Points of Life Cycle • Cycle: cyst—trophozoite—cyst • Host: human being • Lodgment: large intestine • Infective stage: 4 nuclei cyst • Infective route: mouth

  13. Pathogenesis • Pathogenic factor • Virulence • Species: • E.histolytica (pathogenic species) • E.dispar (non-pathogenic species) • Immunity of host • Bacteria flora

  14. Mechanism: contact lysis • Pathology: flask-like ulcer • Clinical manifestation • Non symptomatic carriers • Intestinal amebiasis: dysentery, colitis • Extraintestinal amebiasis: liver abscess

  15. Diagnosis • Etiological diagnosis: • Stool examination of cyst or trophozoite • Sigmoidoscopy or aspiration • Immunological diagnosis

  16. Epidemiology • Cosmopolitan: 110 population • China: 3%~10%; Rural area>urban • Source of infection: carriers • Transmit route: water contamination • Insects: fly, cockroaches

  17. Prevention and Control • Patients and carriers: • Intestinal amoebiasis —metronidazole • Extra~ amoebiasis —diloxanide • Water & nightsoil control • Insect vector control • Personal hygienic health education

  18. Plasmodium

  19. Introduction • Most important tropical disease • 300 million cases with one million deaths world wide in 1999; • 30 million cases before liberation and 24000 cases reported with 39 death in 2000 in china;

  20. 4 species infecting human • Plasmodium falciparum(恶性疟原虫) • Plasmodium vivax(间日疟原虫) • Plasmodium malariae(三日疟原虫) • Plasmodium ovale(卵形疟原虫)

  21. Life Cycle & Morphology • Cycle in human (intermediate host) • Exoerythrocytic stage(红细胞外期) • Erythrocytic stage(细胞内期)

  22. 红细胞外期(肝细胞内增殖) Exo-erythrocytic cycle （速发型） 子孢子红外裂殖体 裂殖子 sporozoite E-E Schizont Merozoite （迟发型P.v.） 进入红细胞 P.v. 8d; P.f. 6d; P.m. 12d

  23. 红细胞内期(RBC内增殖) Erythrocytic cycle • 发育：环形滋养体 大滋养体 (Ring form) (Trophozoite) • 增殖：早期裂殖体(Immature schizont) RBC内发育 成熟裂殖体(子) 配子体形成 (Mature schizont) M吞噬

  24. Scanning electron micrograph of Plasmodium-infected red blood cells. One cell has burst open, releasing merozoites

  25. P.v P.f P.m P.o

  26. 红内期周期 • P.v. 48h • P.f. 36-48h • P.m. 72h 成熟裂殖体内裂殖子数和形态 • P.v. 12-24个，不规则 • P.f. 8-36个，不规则 • P.m. 6-12个，菊花状

  27. 配子体形成(Gametocyte form) • 红内期裂殖子 雌雄配子体 P.v. 2-3d P.f. 7-10d • <12个/mm3不能传播

  28. 被寄生RBC的变化 • P.v. 胀大 薛氏小点 • P.f. 正常 茂氏点 • P.m. 正常 西门氏点

  29. 疟原虫对RBC的选择 • P.v. 幼稚红细胞 • P.f. 各种红细胞 • P.m. 衰老红细胞

  30. Cycle in female anopheline mosquito (definitive host)

  31. 蚊体内发育(有性) Grouth in the mosequito 雌配子体 Gametocyte 雌雄配子受精 雄配子体 (Gametogony) 动合子Ookinete合子 Zygote 卵囊Oocyst（内含子孢子Sporozoite）

  32. 疟原虫发育过程 SporozoiteSchizont 子 Ring formTrophozoite Oocyst吞噬merozoiteSchiont OokineteZygoteGameteGametocyte(female/male) (动合子) (合子) (配子) (配子体)

  33. Infective form: Sporozoite • Period of one erythrocytic stage: • P.V 48h; P.M 72h; P.F 36-48h • Resting stage of sporozoite of P.V & P.O: • Hypnozoite (brady sporozoite) in liver cell

  34. Morphology

  35. P.v P.f P.m P.o

  36. Pathogenesis • Primary attack • Infected erythrocyte rupture products of schizont, stimulate the release of cytokines (TNF)  paroxysm (shiver, fever, sweat)

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