1. Protozoa

2. General Properties of protozoa
Protozoa are one-celled animals with full vital functions.
They may be freeliving or parasitic.
Protozoa are minute parasites and can only be visualized under the microscope.

3. Basic structure
Protozoa, the whole body consists of a singular cell. A protozoan cell is composed of :
1)plasma membrane
2)cytoplasm : a. ectoplasm(外质) b. endoplasm(内质)
3)nucleus
ectoplasm(外质): The ectoplasm is the outer layer with function of protection, locomotion and sensation.
endoplasm(内质): The endoplasm is the inner layer containing food vacuoles(食物泡) and cellular organelles (细胞器). It bears mitochondria (线粒体) , endoplasmic reticulum (内质网), Golgi apparatus (高尔基体) and so on. The endoplasm helps in nutrition and reproduction.

4. Life cycle patterns One-host form (direct) Two-host form (indirect)
One stage form – Trophozoite
Two stage form – Trophozoite & Cyst
Two-host form (indirect)
Mammals mammals
Mammals insect vectors
The life cycle of protozoa can be divided into two types.

5. Locomotion(运动):
flagella(鞭毛)
cilia(纤毛)
pseudopodia(伪足).

6. Pathologic characteristics of protozoa
1. Multiplication (增殖)
2. Diffusion (disperse )
3. Opportunistic pathogen (机会致病)
Classification of protozoa:
According their locomotion organelles, protozoa can be divided into four groups: Amoebae, flagellates, ciliates and sporozoan.
protozoa reproduce in their host, when the number is enough, they may destroy the infected cells

7. Ecological Niches in the Human Body:
1. Skin: Leishmania
2. Eye: Acanthamoeba
3. Mouth: Amoebae and flagellates
(usually non-pathogenic)
4.Gut: Giardia, Entamoeba (and invasion to liver), Cryptosporidium, Isospora, Balantidium
5. Genitourinary Tract : Trichomonas

8. Ecological Niches in the Human Body:
6. Bloodstream: Plasmodium,
Trypanosoma
7. Spleen: Leishmania
8. Liver: Leishmania, Entamoeba
9. Muscle: Trypanosoma cruzi
10. central nervous system : Trypanosoma, Naegleria, Toxoplasma, Plasmodium

9. Medical Protozoa Pathogenic Opportunistic parasite
Not normally pathogens
Become pathogenic due to impairment of host resistance
Clinical importance of the AIDS epidemic
Opportunistic parasites
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

10. Pathogenic Intestinal Amoeba
Entamoeba histolytica
溶组织内阿米巴

11. 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

12. Entamoeba histolytica
granular
endoplasm
ectoplasm
Entamoeba histolytica

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

14. E. histolytica trophozoite
Ingested RBC
endoplasm
Nucleus with central karyosome and fine regular granules(peripheral chromatin granules), evenly distributed around the nuclear membrane
Ectoplasm,Pseudopod
E. histolytica trophozoite

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

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

17. E.histolytic cyst (schematic diagram)
Spherical or round in shape, 10-20um in diameter, cyst wall
1-2 nuclei (immature cyst); 4 nuclei (mature cyst-infective stage).
Glycogen vacuole food reservoir
(brownish-yellow,iodine stained)
chromatoid bodies with blunt, rounded ends in immature(young) cyst

18. E.histolytic cyst (schematic diagram)
4 ring-like nuclei with finely divided peripheral chromatin ,
glycogen vacuole and
chromatoid bodies disappear
Cyst wall and round shape
Mature E. histolytica Cyst

19. E.histolytic cyst (under high power microscope)

20. E. histolytica Stages - CYSTS
Infective Stage for humans
The stage of discharge
Diagnostic Stage in formed stools
Resistant to external surroundings

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

22. The life cycle of E. histolytica is simple and is completed within a single host, which is human body
Man got infected by ameba through ingestion of water and food contaminated with mature cysts. In the small intestine. the cyst became the trophozoites . The trophozoites grow and multiply by binary fission. They then colonise in the large intestine.
Usually, the trophozoites never cause disease. As trophozoites pass down the digestive tract, trophozoites will turn into cysts again. Cyst is not infectious.
However, when the man body's immune system is impaired or there are damages on the intestinal wall, the trophozoites may invade the tissue of the intestine and produce characteristic lesions in the colon. It will the be excreted in the feces

24. Life cycle The basic generation-cycle: cyst –trophozoites – cyst
Trophozoites may invade intestine and spread
Infective cysts and trophozoites pass in feces

25. Life Cycle 1 infective stage: mature cyst 2 access: mouth
3  ecological niches:  large intestine; liver, lung and other organs.
4  pathogenic stage:  trophozoite
5  diagnostic stage:  cyst; trophozoites

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

27. Clinical Classification of Amebiasis (World Health Organization)
Asymptomatic (intestinal) "Cyst Passers”
Symptomatic Infection:
Intestinal Amebiasis: (dysentery, colitis)
Acute Dysenteric (dysentery)
Chronic Non-Dysenteric (“self-cured”)
Extra-Intestinal Amebiasis:
Amebic Liver Abscess (ALA)
Amebic Pulmonary Abscess
Other sites (brain, skin, GU,)

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

29. Acute Dysenteric Amebiasis
Symptoms:
Bloody mucoid diarrhea
RBCs and few WBCs in stools
Abdominal pain
weight loss
Bloating(胃气涨), tenesmus(里急后 重) and cramps (痉挛)

30. Acute Dysenteric Amebiasis
Signs:
Fever (33%)
Tender (enlarged) liver
Stools positive for trophozoites +/- WBC
NOT cysts in loose stools

31. Clinical manifestation
Pinpoint lesion on mucous membrane
Flask-shaped crateriform (volcano)ulcers

32. Chronic Non-Dysenteric Amebiasis
“self-cured” carrier state
Usually for 1 year, 37% symptomatic >5 years
Intermittent diarrhea, mucus stool, abdominal pain, flatulence and/or weight loss
E. histolytica trophs (rarely cysts) in stools
Positive serology and ulcerations on sigmoidoscopy or pathology test

33. Amebic Liver Abscess (ALA)
Extra-Intestinal Amebiasis
Amebic Liver Abscess (ALA)
Symptoms
History of dysentery (1 yr), wt loss, abdominal pain, chest or shoulder pain
Signs
fever, hepatomegaly 肝肿大
Might find trophozoites in the aspirate
Skin inflammation

34. Extra-intestinal amoebiasis
Hepatic 
(1) acute non-suppurative
    (2) liver abscess: right upper quadrant pain, referred to the right shoulder. tender.
Pulmonary
Brain
Skin, perianal infection
Other extra-intestinal amoebiasis

35. Clinical manifestation

36. Clinical manifestation

37. 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 amebic abscess of liver. Tube of "chocolate" pus from abscess. 

38. 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

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

40. Epidemiology Cosmopolitan世界性的/worldwide
China: 3%~10%; Rural area>urban
Source of infection: carriers
Transmit route: water contamination
Insects: fly, cockroaches

41. Prevention & Control Individual measures
Diagnosis and treatment of E. histolytica patients
no animal reservoirs (other than humans) are known
Safe drinking water (boiling or 0.22 µm filtration)
Cleaning of uncooked fruits and vegetables
Prevention of contamination of foods
Personal hygienic health education

42. E.coli cyst (under high power microscope)

43. trophozoite
cyst
nucleus
E.h
E.c

44. Question 1.How to diagnose hepatic amebiasis?
2.What are the transmission route of E. histolytica ?
3.Who should be treated for amebic infection?

45. Giardia lamblia
It is a pathogen
of digestive tract.

47. Morphology of Giardia lamblia trophozoite
looks like monkey face
adhere to surface of intestinal cell
Median body

48. Trophozoite of Giardia lamblia (under electron microscope)

49. Trophozoite of Giardia lamblia (under high power microscope, stained film)

50. Cyst of Giardia lamblia
Oval-shape,4 nuclei ,
flagella and axostyle can be seen
Cyst wall

51. Giardia lamblia life cycle

52. Life Cycle: One host two-stage life pattern. trophozoites – cyst
The infective stage is the cyst with four nuclei.
The cysts are passed out in the feces
and ingested in contaminated water and food.
Dogs, monkeys and beavers can also be infected , and sometimes may be a source of human infection.
Inhabit the duodenum, upper jejunum.

53. Pathogenesis:
The attachment of G.l to the intestinal mucosa may produce a low grade catarrhal inflammation
& that their mechanical & toxic action may interfere with the absorption of Vit.A & fats.

54. Cause Giardiasis. Children>Adults.
Symptoms ranging from mild diarrhea, flatulence, anorexia, cramp-like abdominal pains & epigastric tenderness etc.
leading to the intestinal malabsorption syndrome. Biliary disease (Cholecystitis), particularly in adults.

55. Laboratory diagnosis:
Finding cysts in formed stools,
trophozoites & cysts in diarrhetic feces.
Concentration methods increase
the chances of detection.
The duodenal content gives a higher
percentage of positive findings.

56. Treatment & Prevention:
The drug of choice is quinacrine
hydrochloride or metronidazole.
Pay attention to personal hygiene.