1. GIT protozoa

2. INTESTINAL PROTOZOA
Ameba:
Entamoeba histolytica
Entamoeba dispar
Entamoeba coli
Entamoeba hartmanni
Endolimax nana
Iodamoeba bütschlii
Flagellates:
• Giardia lamblia
• Dientamoeba fragilis
• Chilomastix mesnili
• Trichomonas hominis
• Trichomonas vaginalis
•(other body sites)
• Enteromonas hominis
• Retortamonas intestinalis
Apicomplexa:
• Cryptosporidium hominis
• Cryptosporidium parvum
Other:
• Blastocystis hominis
• Balantidium coli
unicellular eukaryotic
organisms

3. Ameba: Formally Phylum Sarcodina
• Protozoa with pseudopodia (or if not, distinct
locomotive protoplasmic flow present).
• Mitochondria when present never in the form of a
kinetoplasts.
• Without apical complex.
• Without axostyles.

4. Ameba Diversity
• Most amoebas are harmless single cell
protozoans living in mud, water, and soil
feeding on other protozoans and
bacteria.
• Some species are parasitic and
endocommensals and are quite common
inhabitants of animals.

5. Endocommensal and Parasitic
Ameba Diversity
• Domestic animals
• Birds are free
• Reptiles  one species that is pathogenic
in snakes Entamoeba invadens
• Frogs and salamanders
• Leeches, termites, and cockroaches
• Hydra
• Humans

6. Some Ameba are Pathogenic
• Amebiasis- The pathological condition of
having an amoebic infection.
• -iasis- “indicates a pathological
condition”

7. Entamoeba histolytica

8. Entamoeba histolytica
• One of the most important and
pathogenic parasites of humans.

9. Entamoeba histolytica
• One of the most important and
pathogenic parasites of humans.
– Although dogs, cats and primates may be infected,
these infections are rare and unimportant. This
parasite is primarily a human parasite and is
transmitted from human to human.

10. Entamoeba histolytica
•
One of the most important and pathogenic parasites of humans.
– Although dogs, cats and primates may be infected, these
infections are rare and unimportant. This parasite is
primarily a human parasite and is transmitted from human to
human.
• First seen in 1878 but not described until
1903.

11. Entamoeba histolytica
•
One of the most important and pathogenic parasites of humans.
– Although dogs, cats and primates may be infected, these
infections are rare and unimportant. This parasite is
primarily a human parasite and is transmitted from human to
human.
•
First seen in 1878 but not described until 1903.
• Causative agent of the disease amebiasis
(old name is Amebic Dysentery).

12. Entamoeba histolytica

13. Entamoeba histolytica
Trophozoite: 20-30 µm
• Active, feeding stage
• Growing stage
• Amoeboid with blunt
pseudopodia
• Non-foamy cytoplasm
• Uninucleated; nucleus
with fine peripheral
chromatin granules,
small central endosome

14. Entamoeba histolytica Trophozoites

15. Entamoeba histolytica
• Dormant/resistant
stage
• Spherical
• 1-4 nuclei, (4 in
mature cysts)
• Bluntly rounded
chromatoidal bars
Cyst:10-20 μm

16. Entamoeba histolytica Cysts

17. Entamoeba histolytica Cysts
Uninucleate cyst
Binucleate cyst

18. Entamoeba histolytica Cysts
Quadrinucleate or mature cysts

19. Ameboid Movement
• Ameboid locomotion is used by certain
protists including parasitic amoeba.

20. Complex changes in cell
fine structure, chemistry,
and behavior.
(gel-like)
(more fluid)

21. Mechanisms of Ameboid Movement

22. Mechanisms of Ameboid Movement

24. Entamoeba histolytica Life Cycle

25. Entamoeba histolytica Life Cycle
• INFECTIVE STAGE: Cyst

26. Entamoeba histolytica Life Cycle
• INFECTIVE STAGE: Cyst
• Cysts are susceptible to heat (above 40
°C), freezing (below –5 °C), and drying.

27. Entamoeba histolytica Life Cycle
• INFECTIVE STAGE: Cyst
• Cysts are susceptible to heat (above 40 °C), freezing
(below –5 °C), and drying.
• Cysts remain viable in moist
environment for 1 month.

28. Entamoeba histolytica Life Cycle
• CYST: ingested with fecal
contaminated food or
water.

29. Entamoeba histolytica Life Cycle
• CYST: ingested with fecal
contaminated food or water.
• Excystation occurs in the
small intestine in an
alkaline environment.

30. Entamoeba histolytica Life Cycle
•
CYST: ingested with fecal
contaminated food or water.
•
Excystation occurs in the small
intestine in an alkaline environment.
• Metacystic amebas
emerge, divide and move
down into the large
intestine.

31. Entamoeba histolytica Life Cycle
• Trophozoites colonize the
large intestine and invade
the mucosa.

32. Entamoeba histolytica Life Cycle
•
Trophozoites colonize the large
intestine and invade the mucosa.
• They live within the crypts
and mucosa of the large
intestinal lining.

33. Entamoeba histolytica Life Cycle
•
Trophozoites colonize the large
intestine and invade the mucosa.
•
They live within the crypts and mucosa
of the large intestinal lining.
• Trophozoites may live and
multiply indefinitely within
the crypts of the LI mucosa
feeding on starches and
mucous secretions.

34. Entamoeba histolytica Life Cycle
• Cysts form in response
to unfavorable
(deteriorating)
environmental
conditions, as they move
down the LI.

35. Entamoeba histolytica Life Cycle
• Cysts form in response to
unfavorable (deteriorating)
environmental conditions, as
they move down the LI.
• They are released in
formed feces.

36. Entamoeba histolytica
• E. histolytica has surface enzymes that
can digest epithelial cells and therefore
hydrolyze host tissues and cause
pathology.

37. Entamoeba histolytica
• E. histolytica has surface enzymes that can digest
epithelial cells and therefore hydrolyze host tissues and
cause pathology.
• Usually the hosts’ repair of the epithelial
cells can keep pace with the damage.

38. Entamoeba histolytica
•
E. histolytica has surface enzymes that can digest epithelial cells
and therefore hydrolyze host tissues and cause pathology.
•
Usually the hosts’ repair of the epithelial cells can keep pace with
the damage.
• However, when the host is stressed, has
too much HCl, or a high bacterial flora,
the digestion will be ahead of repair.

39. Entamoeba histolytica Pathology
1. A Primary Ulcer Can Occur.

40. Entamoeba histolytica Pathology
1. A Primary Ulcer Can Occur.
Flask Shaped
Ulcers

41. Entamoeba histolytica Pathology
1. A Primary Ulcer Can Occur.
A primary ulcer can cause rupturing of the
bowel and can cause Peritonitis.

42. Shows movement of
trophozoites from large
intestine to liver via hepatic
portal vein.
Liver Abscesses

43. Entamoeba histolytica Pathology
2. Extra-Intestinal
Lesions and Abscess
Occurs

44. Entamoeba histolytica Pathology
2. Extra-Intestinal
Lesions and Abscess
Occurs
A. Hepatic Amebiasis

45. Entamoeba histolytica Pathology
2. Extra-Intestinal
Lesions and Abscess
Occurs
A. Hepatic Amebiasis
B. Pulmonary Amebiasis

46. Entamoeba histolytica Pathology
2. Extra-Intestinal
Lesions and Abscess
Occurs
A. Hepatic Amebiasis
B. Pulmonary Amebiasis
C. Cerebral Amebiasis

47. Entamoeba histolytica Pathology
• Frequently, intestinal lesions will heal
themselves.

48. Entamoeba histolytica Pathology
• Frequently, intestinal lesions will heal
themselves.
• Two exceptions- External ulcers that did
not come from the intestine.
Ocular amebiasis
Genital amebiasis

49. Amoebic Amebiasis of the Skin

50. Symptoms
• 10% of people in the world infected with
ameba, but only 3% ever have some sort
of clinical signs.

51. Symptoms
• 10% of people in the world infected with
ameba, but only 3% ever have some sort of
clinical signs.
• Abdominal discomfort.

52. Symptoms
• 10% of people in the world infected with ameba, but
only 3% ever have some sort of clinical signs.
• Abdominal discomfort.
• Intense pain localized on the right side.

53. Symptoms
• 10% of people in the world infected with ameba, but
only 3% ever have some sort of clinical signs.
• Abdominal discomfort.
• Intense pain localized on the right side.
• Dysentery.

54. So How Bad is This?
• In theory, ingestion of 1 cyst could kill
you.
• In practice, probably it will never
happen.

55. Prognosis
• 90% of time recovery.
- How much damage.
- Body will repair itself but this repaired
connective tissue in bowel will not
function.

56. Diagnosis
• Fecal smear/Nested PCR and monoclonal
antibody methods.
• Biopsy.
• Serological/Immunological tests (ELISA).

57. Seriousness of Diagnosis
• Could expose someone to unnecessary
treatment.
• Will not be treating the real problem.
• There is an expense.
• Time factor.

58. Treatment
• Current drug of choice  Metronidazole
(Flagyl).
• Side effects: Insomnia, headaches,
vomiting, intense vasodilation, mutations
on bacteria, and carcinogenic in mice.

59. Epidemiology
• How an infectious organism spreads
through a population.

60. Entamoeba histolytica
DISTRIBUTION - Parasite has worldwide
distribution but is most common in the tropical and
subtropical areas of the world.

61. Entamoeba histolytica
DISTRIBUTION - Parasite has worldwide
distribution but is most common in the tropical and
subtropical areas of the world.
- it is estimated that up to 500 million people may be
affected.
- may cause up to 100,000 deaths each year.

62. Entamoeba histolytica
DISTRIBUTION - Parasite has worldwide
distribution but is most common in the tropical and
subtropical areas of the world.
- it is estimated that up to 500 million people may be affected.

63. Entamoeba histolytica
• A number of outbreaks have resulted
from a breakdown in sanitation or
behavioral practices of people.

64. Management
• Metronidazole 800 mg three times daily for 5 days is
given in amoebic colitis; a lower dose (400 mg three
times daily for 5 days) is usually adequate in liver
abscess.
• Tinidazole is also effective: dehydroemetine and
chloroquine are alternative drugs, but are rarely used.
After treatment of the invasive disease, the bowel
should be cleared of parasites with a luminal
amoebicide such as diloxanide furoate.

65. Prevention
• Amoebiasis is difficult to eradicate because
of the substantial human reservoir of
infection. The only progress will be through
improved standards of hygiene and better
access to clean water.
• Cysts are destroyed by boiling, but chlorine
and iodine sterilizing tablets are not always
effective.