疟原虫 Plasmodium

1. 疟原虫Plasmodium

4. Plasmodium (Malaria Parasite) • Species susceptible to human: • 1.Plasmodium vivax(Pv): Cause tertian malaria. • 2.P.falciparum (Pf): Cause malignant malaria. • 3.P.malariae (Pm): Cause quartan malaria. • 4.P.ovale (Po): Cause benign malaria.

5. Prevalence: • Malaria is the most important parasitic disease in the world. • 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;

6. Distribution of Malaria in the World

7. The vector – female mosquito

8. Life Cycle

10. Life Cycle

11. Life Cycle

12. Morphology & Life Cycle (Biology Features) • 1.Asexual development(in human host): (1)Exo-erythrocytic stage -EE forms (in liver cells), Sporozoite(Tachysporozoite & Bradysporozoite)-schizont-merozoites. One generation results in numerous.

13. 红外期exo-erythrocytic stage—merozoites in liver cells肝细胞内裂殖体

14. Morphology • Plasmodium is the one-cell parasite, so the basic morphology is a nucleus , cytoplasma and cell membrane • Wright or Giemsa stain gives the Cytoplasm – blue; nucleus - red , while the malarial pigments are yellow-brown • There are three stages and six main forms of plasmodium in RBC

15. P.vivax in RBC • three stages and six main forms • 滋养体期(trophozoites)：ring form and developing trophozoites • 裂殖体期(schizonts)：immature and mature schizont-- merozoites • 配子体期(gametocyte)： Microgametocytes and macrogametocytes

16. Ring form of P.v.

17. Amoeboid form of P.v.

18. Schizonts • Figs.： increasingly mature schizonts

19. Immature schisont of P.v.

20. merozoite hemozoin Mature schizont: nucleus divided into 12-24 (16), cytoplasm divided, each nucleus surrounded by a portion of cytoplasm to form merozoites, hemozoin clumped

21. Oval in shape, light blue cytoplasm is abundant compact nucleus, usually at edge of the parasite scattered pigment granules The gametocyte is completely filling its host cell Female gametocyte of P.v

22. Male gametocyte of P.v • Oval in shape, blue cytoplasm is abundant; • Loose and large nucleus (chromatin), central in position • Malarial pigments diffuse • Infected RBC enlarged and became pale with red Schüffner‘s dots

23. Female gametocyte of P.v.

24. Male gametocyte of P.v.

27. P.falciparumring form

28. P.f ring form • Fine ring , smaller,about 1/5 of RBC diameter, • Usually multiple infection • 1-2 small nucleus • Infected RBC is normal,almost no change

29. P.f. macrogametocyte • Compact nucleus, red, usually at the center of the cell • Malarial pigments around the nucleus • The crescent-shaped gametocytes of P. falciparum are very distinctive, but tend to only appear late in the infection

30. Pf. microgametocyte • Large, diffuse nucleus at the center • Sometimes hard to distinguish from the female gametocytes • Sausage-shaped with two blunt end

31. P.f.

32. The Features of Erythrocytic Stage: • a. Repeated generation. • b. Synchronous development. • c. Definite time duration: Pv 48h; Pf 36h-48. • d. The stage responsible for pathogenesis.

33. Male gametes

34. ookinetes

35. Oocysts

36. Oocysts of P. falciparum in midgut of an infected mosquito. Oocysts appear as circular bodies. Fresh preparation. ×100. Enlarged by 5.4.

37. Sporozoites

38. Malarial paroxysm(疟疾发作) • An attack occurs because of the sudden liberation of merozoites, malarial pigment and RBC debris into the blood stream.

39. Pathogenesis Clinical features Typical malaria paroxysm • symptom for erythrocytic phase • shaking chill （寒战）followed by fever （高热）(2-20 hrs) • RBCs rupture releasing merozoites, malarial metabolites, endotoxin in blood, the pyrogens • profuse sweating when fever breaks （出汗退热） • repeated characteristic cycle for each species

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

41. Recrudescence(再燃) • It is a recurrence of symptoms in a patient whose blood stream infection has previously been at such a low level as not to be clinically demonstrable or cause symptoms.

42. Relapse(复发) • It is a recurrence that taken place after complete initial clearing of the erythrocytic infection and implies reinvation of the blood stream by merozoites from activated hypnozoites in liver.

43. Complications • Anemia • Hemolysis of infected erythrocytes • Hypersplenism • Autoimmunization of uninfected erythrocytes • supression of blood production in marrow • Splenomegaly • Malarious nephrosis • fatal malaria-cerebral malaria caused by P.f. (small vessels are plugged)

44. typical splenomegaly syndrome

45. Cerebral malaria

46. Diagnosis • Travel history to endemic area & presence of symptoms, e.g., fever and chills • Etiological- Microscopic examination of blood Thin and Thick film (Giemsa's stain) To master the morphology of parasites and changes of infected red cells • Immune probe-Species McAb based assays. • DNA probes- hybridization

47. 实验诊断 Laboratory diagnosis 1．病原检查 （1）ThinfilmThick film Question: Which stages are there in the blood film of P.v. or P.f. ?

48. Epidemiology Distribution: Africa, Asia, Latin America Endemic factors (1)Source of infection: Patients and carriers. (2)Vector host: mosquito (3)Susceptible population (4) resistance of plasmodium to antimalarial drugs. (5) Other transmission mode: by transfusion, congenital transmission

49. Treatment • Antimalarial drugs: • (1)Anti-attack drugs: Kill E-forms-Quinine,Chloroquine. • (2)Anti-recurrence drugs: Kill EE-forms-Primaquine. • (3)Chemoprophylaxis: Kill sporozoite & EE-forms with long shelf life-pyrimethamine 乙胺嘧啶. • affect parasite in different ways depending on stage when administered • emergence of drug-resistant malaria

50. Prevention and control • Control of the source of infection by chemotherapy • Prevention: breaking the human-mosquito-human cycle • mosquito control or eradication - not easy • Personal protection- netting, repellents, etc. avoidance of infected mosquitoes (bed nets , mosquito repellents)