1. Protozoa (原虫)

2. General Account
One-cell animal – monocellular or unicellular organisms with full vital functions
Species – total named species:65,000; parasitic: around 10,000

3. Classification of protozoa
Amoebae
Flagellates
Sporozoa
Ciliates

4. Life cycle patterns One-host form Two-host form
One stage form – Trophozoite
Two stage form – Trophozoite & Cyst
Two-host form
Mammals mammals
Mammals insect vectors

5. Mode of Reproduction Asexual Reproduction Sexual Reproduction
Binary fission – result in 2 daughter cells
Schizogony – multiple fission result in multiple cells
Budding
Exogenous budding - by external budding result in multi- cells
Endodyogony - by internal budding result in 2 cells
Sexual Reproduction
Conjugation – exchange of nuclear material of 2
Gametogony – sexually differentiated cells unite -- zygote

6. Opportunistic & Accidental (protozoa) infections
Pathogenesis
Opportunistic & Accidental
(protozoa) infections
Host Resistance
Innate immunity
Acquired immunity
Parasite Invasion
Toxin
Mechanically damage
Immune impair
Immune inhibition
hypersentivity

7. Opportunistic parasites
Opportunistic infection
An infection by a microorganism that normally does not cause disease but becomes pathogenic when the body's immune system is impaired and unable to fight off infection

8. Amoebic Infections
Entamoeba histolytica
Acanthamoeba
Naegleria

9. Epidemiology
4th leading cause of death from parasitic diseases worldwide
Organism # of deaths/yr # infected
Entamoeba ~75,000 ~300 million
Ascaris ~200, ~480 million
Schistosoma ~750,000 ~200 million
Plasmodium 2-3 million ~500 million
(Malaria)
Amoebiasis is not restricted to the tropics and subtropics, it also occurs in temperate and even in arctic and antarctic zones

10. Contaminated water is a source of infection.

11. Infection is common in developing countries where sanitation is poor.

12. Amoeba in alimentary tract
Entamoeba
E. histolytica (pathogenic)
E. dispar (non-pathogenic)
E. coli (big sister)
E. hartmani (little brother)
E. gingivalis (oral)
Endolimax nana (occasionally pathogenic)
Iodamoeba butschlii

13. Morphology

14. Morphology E. histolytica trophozoite Ingested RBC Endoplasma
Ectoplasma
Nucleus with central karyosome and finely divided chromatin granules
Pseudopod
E. histolytica trophozoite

15. Trophozoites Morphology Single nucleus with a central,
dot-like karyosome

16. Micrograph of a trophozoite ingesting a red blood cell deprived from its host.

17. Morphology
1-4 ring-like nuclei with finely divided peripheral chromatin
Cyst wall and round shape
Mature E. histolytica Cyst

18. Morphology

19. Morphology
E. Coli trophozoites

20. E. Coli cysts
Morphology

21. E. histolytica Stages - CYSTS
Infective Stage for humans
Resistant walls maintain viability
If moist can last several weeks
Killed by desiccation or boiling
Diagnostic Stage in formed stools
Can be concentrated and stained easily
Not seen in liquid (diarrheic) stools or tissues

22. E. histolytica Stages - TROPHOZOITES
Cause amoebiasis (damage tissue)
Spread throughout the body, but ...
Rarely transmit the infection to others
Labile in liquid stools or tissue, and
must be rapidly found or preserved (quick fixation & cold storage) for Diagnosis

23. Life cycle

24. Life cycle Humans acquire E. histolytica by:
Ingesting cysts (4 nuclei mature) in fecally contaminated food or water
Rarely by directly inoculating trophozoites into colon or other sites
(anal sex?)
Fecal-Oral transmission (hand to mouth)

25. Life cycle
The basic generation-cycle: cyst – lumen trophozoites – cyst
Trophozoites may invade intestine and spread
Cyst formation – essential factors: enviroment + time
Infective cysts and trophozoites pass in feces

26. Pathogenesis General Types of Virulence Factors: Adherence factors
260kDa Gal/GalNAc lectin
Invasion factors
Amoeba pores
Cysteine proteinases
Endotoxins

27. Pathogenesis Trophozoites ... Attach to mucosal epithelial cells (MEC)
Lyse MEC
Ulcerate and invade mucosa
Cause dysentery (diarrhea + blood)
Metastasize via blood &/or lymph to
Form abscesses in extraintestinal sites ...

28. Clinical Classification of Amoebiasis (World Health Organization)
Asymptomatic Infection:"Cyst Passers/carrier”
Symptomatic Infection:
Intestinal Amoebiasis: (colon and rectum盲肠、 升结肠、直肠、乙状结肠和阑尾)
Acute Dysenteric (dysentery)
Chronic Non-Dysenteric (“self-cured”)
Extra-Intestinal Amoebiasis:
Amoebic Liver Abscess (ALA)
Amoebic Pulmonary Abscess
Other sites (brain, skin, GU, ?)

29. Clinical classification
Asymptomatic infection (carrier)  >90% (E. dispar?)
Symptomatic cases <10%
8% -10% dysentery, colitis, etc
2% invasive amoebiasis
0.1% deaths

30. Acute Dysenteric Amoebiasis
Clinical manifestation
Symptoms:
Bloody mucoid diarrhea
RBCs and few WBCs in stools
Abdominal pain
weight loss
bloating, tenesmus(里急后重) and cramps

31. Acute Dysenteric Amoebiasis
Clinical manifestation
Signs:
Fever (33%)
Tender (enlarged) liver
Stools positive for trophozoites +/- WBC
NO cyst in loose stools

32. Clinical manifestation
Pinpoint lesion on mucous membrane
Flask-shaped crateriform ulcers
Pathological changes in large intestine

34. Chronic Non-Dysenteric Amoebiasis
Clinical manifestation
Chronic Non-Dysenteric Amoebiasis
“self-cured” carrier state
Usually for 1 year, 37% symptomatic >5 years
Intermittent diarrhea, mucus, abdominal pain, flatulence and/or weight loss
E. histolytica trophs in loose stools
Cysts in solid stools
Positive serology and ulcerations on sigmoidoscopy or pathologic test

35. Amoebic Liver Abscess (ALA)
Clinical manifestation
Extra-Intestinal Amoebiasis
Amoebic Liver Abscess (ALA)
Symptoms
History of dysentery (1 yr), weight loss, abdominal pain, chest or shoulder pain
Signs
fever, hepatomegaly
Diagnostic aspiration:non-odorous, reddish-brown in color aspirate (chocolate jam) "anchovy paste"
Might find trophozoites in the aspirate
Skin inflammation

36. Clinical manifestation
Ulcers caused by invasion of E. histolytica into the liver.

37. Clinical manifestation

38. Clinical manifestation

39. An Amoebic Liver Abscess Being Aspirated.
Note the reddish brown color of the pus (‘anchovy-sauce’). This color is due to the breakdown of liver cells.
Gross pathology of amoebic abscess of liver. Tube of "chocolate" pus from abscess. 

41. X-ray of Amoebic Liver Abscess
Clinical manifestation

42. Diagnosis Pathogenic diagnosis
Stool examination:
Direct Fecal Smear (trophs and cysts)
Fecal concentration and iodine dye techniques - (cysts) ZnSO4 or formalin-ether
Cultivation
DNA detection
Sigmoidoscopy
Serologic Tests (for chronic disease): ELISA, IHA (indirect hemagglutination)
Imaging: X-ray; CT

43. Stool examination trophozoite cyst loose feces solid feces
specimen
loose feces
solid feces
method
direct smear with normal saline
direct smear with iodine stain
diseases
amoebic dysentery
chronic intestinal amoebiasis or carriers
remarks
1.container must clean 2.examined soon after they have been passed. 3.select bloody and mucous portion.

44. Two microscopically indistinguishable Entamoeba sp.
E. histolytica
invades tissues
should always be treated
E. dispar
is non-pathogenic, even in AIDS
should not be treated

45. Treatment of Amoebiasis
For invasive forms: metronidazole
For luminal forms: Iodoquinofonum, paromomycin, diloxanide
Do not treat asymptomatic intestinal E. dispar infection

46. Treatment of Amoebiasis

47. Prevention & Control Individual measures Chemotherapeutic Trial
Diagnosis and treatment of E. histolytica patients
Safe drinking water (boiling or 0.22 µm filtration)
Cleaning of uncooked fruits and vegetables
Prevention of contamination of foods
Chemotherapeutic Trial

48. Community measures Prevention & Control Public services and utilities
Adequate disposal of human stools
Safe and adequate water supply
Primary health care systems
Health education (washing hands, cleaning and protecting food, controlling insects)
Specific surveillance programs and Control programs integrated into ongoing sanitation & diarrhea control
Health Regulations
Control of food vendors and food handlers
Control of flies and cockroaches

49. Infections with Free Living Amoebae
Naegleria 耐格里属
Acanthamoeba 棘阿米巴属

50. Free Living Amoebae Not seen in humans Naegleria
10-35 µm (smaller than A. spp.) with lobate pseudopodia
Acanthamoeba cysts & trophs are seen in humans i
15-45 µm with filiform pseudopodia

51. Acanthamoeba spp.
Acanthamoeba trophozoites with acanthopodia

52. Primary Amoebic Meningoencephalitis PAME
An acute suppurative infection of the brain and meninges that is rapidly fatal and usually not diagnosed antemortem
Caused by Naegleria fowleri
Headache, lethargy and olfactory problems
Sore throat, runny nose, severe headache, vomiting, stiff neck, confusion leading to ...
Coma and death

53. DIAGNOSIS Patient History (child) Symptoms/Signs PAME
Prior Health Excellent
Recent History of Swimming (fresh water/pools)
Cases peak during HOT months
Symptoms/Signs
Sore throat, runny nose, headache, vomiting, stiff neck, mental confusion, olfactory problems, lethargy, coma and death

54. Treatment PAME None effective - few patients survive
Amphoteracin B +/- ?

55. Granulomatous Amoebic Encephalitis GAE
A more slowly progressive, chronic form of the disease not associated with swimming (except in hot tubs)
cause: Acanthamoeba castellanii
history of subcutaneous nodules, eye or skin infection, progressive nasal congestion, headache ...
CNS lesions with negative serology for toxoplasmosis
in debilitated/immuno-compromised Pts with CD4+ TL <200/mm3
disseminated infection: skin, sinuses, lungs, CNS/CSF

56. Pathology abscesses/lesions (tissues) have amoebae rarely seen in CSF
GAE
Pathology
abscesses/lesions (tissues) have
granulomatous inflammation
hemorrhagic necrosis and vasculitis
trophozoites & cysts with wrinkled-walls!
amoebae rarely seen in CSF

57. GAE
Treatment
No satisfactory or effective treatment ?
amphotericin B

58. Acanthamoeba Keratitis AK
Corneal infection with Acanthamoeba spp. trophozoites & cysts
Ulcerations & “Ring Infiltrate” of cornea
Induced by
trauma to eye, exposure to contaminated H2O
contact lens wear with tap water rinsing

59. AK Diagnosis Treatment Examine corneal scrapings or smear
Histopathologic examination of cornea
Treatment
Triple Antiamoebic Therapy
neomycin-polymyxin-gramicidin/propamidine/miconazole
Penetrating keratoplasty (cadaver cornea)

60. Summary E. histolytica Free living amoeba
Life cycle, pathogenesis, Diagnosis, treatment
carrier
Morphology differences with E. coli
Free living amoeba
prevention

61. QUESTIONS How to diagnose hepatic amoebiasis?
What are the transmission route of E. histolytica ?
Who should be treated for amoebic infection?
How will one get amoebiasis? What are the consequences?