This document provides a classification and overview of intestinal protozoa including Entamoeba, Giardia, Dientamoeba, Trichomonas, and Balantidium. It describes the morphology, life cycles, pathogenicity and clinical manifestations of Entamoeba histolytica, the causative agent of amebiasis. Laboratory diagnosis and treatment options for intestinal amebiasis and extraintestinal complications like hepatic amebiasis are also summarized. The document briefly mentions other non-pathogenic intestinal amoebae including Entamoeba coli, Entamoeba dispar, Entamoeba hartmanni, Entamoeba gingivalis, Endolimax n

1. Intestinal protozoa ( Entamoeba,
Giardia, Dientamoeba ), Genital
Flagellates ( Trichomonas ) & Ciliata
Dr. Rubaiya Binte Kabir
MPhil (part 1)
DMP - 15

3. Classification
1. The Amoeba :
i) Entamoeba histolytica
ii) Entamoeba coli
iii) Entamoeba disper
iv) Entamoeba hartmanni
v) Entamoeba moshkovskii
vi) Entamoeba polecki
vii) Entamoeba gingivalis
viii) Endolimax nana
ix) Iodamoeba butschlii

4. 2. The Flagellates :
i) Giardia lamblia
ii) Diantamoeba
iii) Chilomastix mesnili
iv) Trichomonas hominis
v) Enteromonas hominis
vi) Retortamonas intestinalis.
3. The Ciliata :
Balantidium coli

5. Pathogenic Intestinal Amoeba :

6. Entamoeba histolytica :
It was first described in 1875 by Fedor Losch
from Russia and named by Frits Scaudinn in 1903.
Epidemiology :
- Prevalence is close to 1-5% worldwide. Most
common in tropical countries, especially in areas with
poor sanitation. Also widely prevalent among
homosexuals.
- Third most common parasitic cause of death in
the world.

7. -Approximately 50 million cases and 110,000
deaths are reported by WHO annually.
Distribution :
The organism is acquired by ingestion of cyst
that differentiated into trophozoite in the ileum
but tends to colonize the ceacum and colon.

8. Morphology :
Has three stages : 1. Trophozoite
2. Precyst
3. Cyst.
Trophozoite :
1. Anaerobic parasite ; invasive form as well as the
feeding and replication form found in the feces
of patients with active disease.
2. size : vary from about 12-60μm in diameter.

9. 3. Cytoplasm :

10. - divided into clear glass like ectoplasm and
granular endoplasm.
- phagocytic stomata : endocytic food cups,
present on the surface and used in engulfment.
- freshly ingested erythrocytes : appear as pale
greenish, refractile bodies.
- pseudopodia : cytoplasmic protrution,
characteristically hyaline when first formed.
- lack of mitochondria, ER, golgi apparatus

11. - identification : 1. when stained with
hematoxylin : grayish and erythrocytes are
progressively paler.
2. when stained with
trichrome : typically green and cherry- red or
green erythrocyte.

12. 4. Nucleus :
- single, spherical.
- size : 4-6μm.
- karyosome : a small mass of chromatin in the
center.
- peripheral chromatin : a layer of granule on the
inner surface of nuclear membrane.
- between karyosome and peripheral chromatin
there is a faintly stained fibrils of the linin network
(cart wheel appearance).
- nuclear membrane : delicate and distinct.

13. -identification :
1. when stained with hematoxylin : intense
bluish black.
2. when stained with trichrome : dark red.

14. Precyst :
1. smaller to trophozoite but larger to cyst (
10-20μm).
2. oval with a blunt pseudopodia.
3. food vacuoles and RBCs disappear.
4. single rounded nucleus, absence of
ingested materials and lack of a cyst wall.

16. Cyst :
1. presence of hyaline cyst wall which
appears highly refractile when unstained.
2. shape and size : spherical, sometimes
ovoid or irregular; vary from 10-20μm in
diameter.
3. Nucleus :
- 1-4 or rarely more.
- peripheral chromosome :
peripheral chromatin ring may appear
thicker and less uniform, may form thin
plaque on nuclear membrane or may
massed in crecent fashion at one side of
nuclear membrane.

17. - karyosome : eccentric.
- identification : when stained, nuclear
structure is similar to that of trophozoite.
4. Cytoplasm :
- Chromatoidal bars : rod shaped with
rounded/squared ends; large number in
mononucleated cyst surrounding a glycogen
vacuole.

18. - identification :
1. with iodine : light yellowish green to yellow
brown; chromatoidal bars do not stain; glycogen
valuole is dark yellow brown.
2. with heamatoxylin : chromatoidal bars are
bluish black;
3. with trichrome : chromatoidal bars are bright
red.

19. Life Cycle :

21. Symptoms and Pathogenesis :
Pathogenesis :
Intestinal ameobiasis :
Infective form : cyst.
Incubation period : 4-5days.
Virulances of E. histolytica include :
1. contact dependent cell killing : receptor
mediated adherence to target cell : by amoebic lectin
antigen ( GAL/GALNAG lectin).

22. 2. amoebic cytolysis of target cell : the production
of enzymes or other cytotoxic substances :
histolysin, amoebapain, cathepsin B protease.
3. others : amoebapore, hydrolytic enzymes
(RNAase, neutral protease, phosphatse).

23. Genesis:
Acute:
Liberation of metacystic trophozoite after exystation
Enter the crypts of Lieberkünn
Penetrate directly through the columner epithelium of the
mucous membrane with the help of amoeboid movement
and proleolytic enzymes.
Continuous lysis of tissues till they reach submucous coat.
Begin to pass in various direction dissolving surrounding
tissues.
Ultimately, destroy considerable area of submucosa.

25. Chronic:
1. Small ulcers : involving only mucosa.
2. Extensive superficial ulcers with hyperaemia.
3. Thickening, fibrosis, stricture formation with
scarring of intestinal wall.
4. Extensive adhesion with surrounding viscera.
5. Diffuse pseudotumour like mass of granulation
tissue formation (Amoeboma).

26. Hepatic Amoebiasis:
Infective form : Trophozoite.
Occurs : 1-3 months of intestinal amoebiasis.
Common site : post.-sup. surface of rt. lobe.
Genesis :
Trophozoites are carried as emboli from the base of the
amoebic ulcer at caecum and ascending colon by
radicles of portal veins.
Capillary system acts as efficient filter and holds these
parasites.
Multiply there occluding hepatic venules.
Anoxic necrosis of hepatocytes

27. Inflammatory response surrounding hepatocytes leads to
abcess formation with the help of cytolytic action
which liquefies the solid slough .
 Anchovy sauce pus :
liver abcess pus is thick;
chocholate brown in colour;
acidic and pH 5.2-6.7;
comprised of necrotic hepatocytes, without any
pus cell and and trophozoite.

28. Symptoms :
Clinical classification (WHO report on Amebiasis,1969) :
1. Asymptomatic.
2. Symptomatic :
A. Intestinal Amebiasis : i) Dysenteric
ii) Nondysenteric colitis.
B. Extraintestinal : i) Hepatic – a) acute
nonsuppurative.
b) liver abcess.
ii) Pulmonary
iii) others.

29. Clinical menifestations of Intestinal Amebiasis :
i) Asymptomatic :
- vague and nonspecific abdominal symptoms.
ii) Symptomatic :
a) Dysenteric :
- bloody diarrhoea with mucous and pus cell.
- abdominal pain, cramping, flatulance,
anorexia, wt. loss, chronic fatigue.
b) Nondysenteric :
- amoebic appendicitis : acute right lower
abdominal pain.

30. - Amoeboma : palpable abdominal mass.
- Fulminant colitis : intense colicky pain, rectal
tenesmus, >20 motions/day, fever, nausea, anorexia,
hypotention.
Clinical menifestation of Extraintertinal amebiasis :
i) Hepatic :
a) Acute non suppurative :
- liver tenderness and enlargement.
- fever, wt. loss, cough (with an evidence of
pneumonitis, involving right lower lung field.

31. b) Liver abcess :
- severe and continuous hepatic pain which may
reffered to right or left shoulder.
- hepatomegaly.
- fever.
Clinical menifestation of Pulmonary Amebiasis :
- pleurisy, with or without effusion or pleural rub.
- pneumonia.
- lung abcess.

32. Others :
- Amoebic infection of Skin : cutaneous amebiasis
of the face results in loss of vision of one eye, without
involving the mucocutanous surface.
- Vaginal, urethral, clitoral infections have been
reported along with amebiasis of the penis as a
consequences of anal intercourse or partner with
vaginal amebiasis.

33. Complication :
Intestinal amoebiasis :
1. Fulminant Amoebic colitis.
2. amoebic liver abcess.
3. amoebic appendicitis.
4. Intestinal perforation and peritonitis.
5. perianal skin ulcer.
6. Amoeboma.

34. Amoebic liver abcess :
1. Granuloma cutis : when rupture externally to
skin..
2. Amoebic pleuritis and Pulmonary amebiasis due
to erosion of hepatic abcess.
3. Amoebic pericarditis.
3. Brain abcess (haematogenous spread).

35. Laboratory Diagnosis :
A. Intestinal amebiasis :
1. Stool microscopy by Wet mount, permanent stain to
detect cyst and trophozoite.
2. Stool culture : Polyxenic and Axenic culture.
3. Stool antigen detection : CIEP, ELISA, ICT.
4. Serology : by ELISA – lectin antigen.
by ELISA, IFA – antibody.
5. Isoenzyme (zymodene) analysis.
6. PCR.
7. Non specific : Charcot Leyden crystal in stool
moderate leucocytosis in blood.

36. Charcot Leyden crystal in Trichrome media

37. B. Amoebic liver abcess Diagnosis :
1. Microscopy : detect trophozoite.
2. Stool culture.
3. Antigen detection by ELISA.
4. Antibody detection by IFA,ELISA,CFT,CIEP.
5. Histopathology.
6. Molecular diagnosis : PCR.
7. Ultrasonography.
PAS stain of E. histolytica in pus

38. Prevention :
1. Breaking the chain of transmission.
2. treatment of asymptomatic person who passes
cysts in stool may reduce opportunities of disease
transmission.
Treatment :
1. Metronidazole and Tinidazole.
2. Fluid and electrolyte replacement.
3. Drainage of larger hepatic abcess. CT guided
Percutaneous catheter drainage is usefull both in
resistance cases and perforation.

39. Suggested drug regimen :
Infection Drug and dose
Asymptomatic intestinal
amebiasis
Metronidazole 750mg 3
times daily for 10 days
Or,
Tinidazole 50mg/kg qds for
3days.
Amoebic dysentry, liver
abcess, ameboma
Metronidazole 750mg
3times daily for 10 days
followed by luminal
therapy.
Or,
Tinidazole 2gm p.o. for
3days

40. Nonpathogenic Intestinal Amoeba

41. Entamoeba Coli :
- Previously it is called non pathogenic amoeba
- But now it is called pathogenic amoeba.
- 3 forms : trophozoite, precyst, cyst.
- It causes: Abdominal pain, diarrhoea.
- identification : when stained-
1. trophozoite : nucleus with irregular clumps
of peripheral chromatin; large, irregular, eccentric
karyosome.
2. cyst : typical nuclear structure; splinter
shaped or irregular chromatoidals.

42. Trophozoite of Entamoeba Coli :
(iron hematoxylin stain)
Cysts of Entamoeba Coli :
(iodine mount)

43. Life cycle :

44. Difference between Entamoeba histolytica & Entamoeba Coli
:Charecteristics Entamoeba histolytica Entamoeba Coli :
Trophozoite
1. Size 15-20μm 20-25μm
2. Motility Progressive,directional,with finger like
pseudopodia.
Not progressive; short, blunt
pseudopodium appear to func. more to
ingest food.
3. Cytoplasm Clearly differenciated ectoplasm and
endoplasm.
Not so.
4. Cytoplasmic inclusion RSC, leucocytes, tissue debris, bacteria. Do not contain RBC.
5. Nucleus Small center karyosome, thin nuclear
membrane, lined by fine chromatin
granules.
Large, irregular,eccentric karyosome,
thick nuclear membrane, lined by coarse
chromatin granule.
Precyst
10-20μm, oval,no food vacules, nucleus
same as trophozoiye.
20μm.
Cyst
1. Size 12-15μm 15-25μm
2. Number of nuclei 1-4 1-8
3. Chromosomal body Thick bars with rounded ends. Splinter/ribbon/threadlike with irregular
ends.

45. Entamoeba disper, Entamoeba moshkovskii :
- morphologically indistinguishable from
Entamoeba histolytica, except for presence of
ingested RBC in Entamoeba histolytica.
- usually colonizes in the large intestine but
does not invade intestinal mucosa.
- does not induce antibody production.
- not complement resistant.
- can be distinguished from by isoenzyme
analysis, molecular method and detection of lectin
antigen.

46. Difference between Entamoeba histolytica &
Entamoeba disper :
E.histolytica E.dispar
Microscopy Ingested RBC may be
seen within cytoplasm
of trophozoite and is
diagnostic
No RBC seen within
cytoplasm of trphozoite
In vitro culture Axenic(grows without
bacteria)
Xenic(requires bacteria
for growth in culture)
Co-agglutination Positive Negative
Complement resistance Positive Negative
Zymodemes(Isoenzym
e)
II I & III

47. Entamoeba hartmanni :
- small race varient of Entamoeba histolytica.
- trophozoite : 3- 12μm and cyst 4-10μm.
usually colonizes the large intestine.
Entamoeba gingivalis :
- small (10-15 μm )
- inhabit in mouth.
- only trophozoite form.
- large food vacuoles containing WBCs.
- recovered from : vaginal secretion , oral cavity, pt.
with pyorrhoea alveolaris.

48. Endolimax nana :
- resides in the large intestine of humans and other
animals.
- Trophozoite : 8-10μm, shows sluggish motility.
- Cyst : 6-8μm, 1-4 nuclei; cytoplasm doesn’t have
chromatoidal body or glycogen vacuole.
- nucleus (both trophozoite and cyst) : karyosome
eccentric and irregular from which several achromatic
strands extend to the nuclear membrane. There is no
peripheral chromatin.

49. Iodamoeba butschlii :
- Trophozoite : 12- 15μm; ectoplasm and
endoplasm are not differentiated; cytoplasm more
vacuolated.
- Cyst : 10-20μm; round to oval;
nucleus : central karyosome surrounded by
refractile chromatin granules (bull’s eye or basket
appearance). On permanent smear,
may appear to have a halo around
karyosome;
cytoplasm : large iodin
stained glycogen mass or iodophilic
body; no chromatoid body.

50. Schemic diagram of Trophozoites and cysts of Intestinal protozoas.

51. Free living amoeba

52. Small, free living, widely distributed in soil and
water which can cause opportunistic infections in
men. Only 4 have association with human disease:
1. Naegleria fowleri
2. Acanthamoeba
3. Balamuthia mandrillaris
4. Sappinia diploidea

53. Naegleria fowleri :
‘Brain eating amoeba’ – first described by
physician M. Fowleri and R. F. Carter in 1965.
Morphology :
Two forms : 1. Trophozoite.
2. Cyst.
Trophozoite :
1. size : 8- 15μm.
2. Two forms : amoeboid and flagellated.

54. 1. Amoeboid form :
- only recognizable form in human.
- slug shaped (limex form)and possesses lobopodia.
- granular cytoplasm with food vacuoles.
- nucleus with large nucleilus, central karyosome, no
peripheral chromatin, fine nuclear membrane.
- only replicating form, divides by binary fission.
2. Flagellated form :
- pear shaped; possesses two flagella at the broader
end.
- shows typical jerky or spinning movement.

55. Cyst :
1. size 7- 15μm.
2. surrounded by a thick, smooth double wall.

56. Life Cycle and Pathogenesis :
Infective form : amoeboid form.
Incubation period : 5-7days.
Mode of transmission :
man acquired infection by nasal contamination
during swimming in fresh hot water (pond, river,
lake, swimming pool) or from inhalation of particles
of decaying animal manure.
Genesis:
Amoeboid form invades nasal mucosa, cribriform plate,
resulting in significant necrosis and heamorrhage in
the nasal mucosa and olfactory bulbs.
Travels along the olfactory nerve to reach brain.

57. In the brain:
1. Direct ingestion of brain tissue and by producing
food cups or amoebostome into which the cytopathic
enzymes are liberated.
2. Contact dependent cytolysis mediated by hemolytic
proteins, cytolycins, phoshpholipase enzyme.
Gradually produces an acute suppurative
meningoencephalitis.
Later it becomes hemorrhagic and necrotic.

59. Clinical feature :
Initially-
1. Change in taste and smell.
2. Headache,nausea, vomiting, high fever.
3. Signs of meningeal involvement : stiff neck, positive
kernig’s sign.
Secondary symptoms-
1. confusion, hallucination, lack of attention, atexia,
seizure.

60. Laboratory diagnosis :
1. CSF analysis .
2. Microscopy.
3. Culture on nonnutrient agar.
4. Isoenzyme analysis.
5. Molecular method : PCR
6. Imaging : CT scan, MRI shows
- mark obliteration of cistern,
- diffuse enhancement around midbrain,
subarachnoid space, over cerebrum.

61. Saline mount (flagellated
trophozoite)
Hematoxylin eosin media
(amoeboid trophozoite)

62. Treatment:
1. Amphotericin B 1gm/kg/day.
2. Rifampicin, Azithromycin and also antifungallike
miconazole and vorickg/onazole found to be
effective.

63. Pathogenic Flagellates

64. Giardia lamblia :
It was first observed by A. V. Leeuwenhoekin
1681. It was named after Dr. F. Lambl and Prof. A.
Giard.

65. Epidemiology :
- worldwide distribution, most common in tropics
and subtropics.
- causes both epidemic and endemic intestinal
disease.
- a common cause of ‘traveler’s dirrhoea’.
Distribution :
Duodenum and upper part of jejunum where they
live closely to mucosa.

66. Life cycle :

67. Morphology :
Two forms : 1. Trophozoite.
2. Cyst.

68. Trophozoite :
1. size : 9-21μm long and 5-15μm wide.
2. shape : pear shaped when seen in surface view,
and laterally,sickle shaped.
3. motility : erratic,with a slow oscillation about
the axis ( falling leaf pattern).
4. bilaterally symetrical.
5. Flagella :
- 4pairs : ant., lateral,
ventral, post.
6. sucking disc : modified form
of ant. portion of the ventral surface.

69. 7. median bodies : two curved rods,posterior to
sucking disc
8. axoneme : intracytoplasmic portion of flagella.
9. basal bodies/ blepharoplast : 4 pairs; axonemes
arise from here.
10. parabasal bodies : connected to basal bodies
through which axoneme passes.
11. nucleus :
spherical or ovoid;
large, central karyosome;
no peripheral chromatin.

70. Trophozoite of Giardia lamblia in geimsa stain.

71. Cyst :
1. Size : 8-14μm by 7-10μm.
2. Contains :
4 prominent nuclei;
remnant of exoneme;
basal and parabasal bodies;
4 median bodies;
twice the number of intracytoplasmic
flagellar structure seen in trophozoite (dispersed
in a ‘helter-skelter’ fashion).

72. Cyst of Giardia in trichrome stain.

73. Symptoms & Pathogenicity :
Symptoms :
1. mild diarrhoea, flatulence, anorexia, crampy
abdominal pain, epigastric tenderness.
2. steatorrhoea and full blown malabsorbtion.
3. in severe cases : production of copious light
coloued , fatty stool.
hypoproteinemia
hypogamaglobulinemia.
folic acid and fat soluble vit.
deficiency.

74. 4. in chronic cases : foul smelling diarrhoea.
wt. loss.
growth retardation.
5. extraintestinal menifestation :
urticaria, ant. uveitis, salt and pepper
retinal change and arthritis.

75. Pathogenecity :
Infective dose : 10- 20μm cysts.
Risk factor :
- Children who attend day care centers, including
diaper-aged children
- Child care workers, parents of infected children,
- People who swallow water from contaminated
sources.
- Swimmers who swallow water while swimming
in lakes, rivers, ponds and streams.
- immunodeficiency.

76. Several pathogenic mech. :
- achlorohydia, hypogamaglobulinemia, relative
deficiency in secretory IgA in small intestine
(epithelial brush border) predisposes to giardiasis.
- bacterial colonization of the jejunum potenciates
the damage and responsible for symptomatic
malabsorbtion.
- disaccharidase deficincy leads to lactose
intolerance.
- shortening and blunting of the villi, reduction in
height of the columner epithelial cells of mucosa.
- antigenic variation : variant surface protein (VSP)
helps in evasion of host immune system and
resistance to intestinal protease.

77. Laboratory diagnosis :
1. Stool examination : detects cyst and
trophozoite.
2. Entero test : to detect trophozoite.
3. Antigen detection in stool : ELISA, ICT.
4. Antobody detection : ELISA, IFA.
5. Culture : axenic media, such as diamond’s
media.
6. Molecular method : PCR.
7. Radiological finding : Barrium meal X-ray.

78. Treatment :
1. Metronidazole : 250mg thrice daily for 5days.
2. Tinidazole : 2gm.
3. Nitazoxanide : 500mg twice daily for 3days.
4. Furazolidine : children.
5. Paromomycin : Pregnancy.
6. In pt.s with AIDS and hypogammaglobulinaemia
are refractory to treatment. Prolong therapy with
metronidazole (750mg thrice daily 21 days.)

79. Dientamoeba fragilis :
It is classified as an amoeboflagellate as the
flagellum is internal.
Distribution :
cosmopolitan indistribution with incidence rate
varies from 1.4-19%.
Morphology :
Trophozoite is the only stage.

80. Life cycle :

81. Trophozoite :
1. size and shape : irregular; 7- 12μm.
2. Nucleus :
-binucleated form;
an extranuclear spindle
extends between the two nuclei.
- delicate nuclear membrane.
- no peripheral chromatin.
- at the center a large mass composed of 4-8
separate chromatin granule.
3. Pseudopodia : hyaline, broad and leaflike in
appearance with serrated margins.
4. Motility : progressive.

82. Pathogenesis and Symptoms :