This document provides information about amoebiasis caused by Entamoeba histolytica. It discusses the life cycle, symptoms, diagnosis and treatment. Regarding life cycle, E. histolytica has stages of cysts which are ingested and release trophozoites in the intestines. Trophozoites colonize the intestines and form cysts which are released causing further infections. Symptoms range from asymptomatic to dysentery and liver abscesses. Diagnosis involves examining stool for cysts/trophozoites and imaging abscesses. Treatment includes metronidazole or tinidazole antibiotics. Prevention relies on proper sanitation and water treatment to avoid fecal-oral transmission.

1. AMOEBIASIS
By:
Dr. Mohammed Al-Taj

2. 2
AMOEBAE
Six parasites of man belong to this group:
* Entamoeba histolytica
* Entamoeba coli
* Entamoeba gingivalis (oral)
* Entamoeba hartmanni
* Endolimax nana
* Iodamoeba butschlii
(non-pathogenic)
(pathogenic)

3. INTESTINAL PROTOZOANS
Transmission: direct fecal/oral
route.
Developmental stages:
–Trophozoite:
•motile, feeding stage.
•reproduces by binary fission.
–Cyst: -
•resistant stage, infective for humans.

4. Entamoeba histolytica
Pathogen

5. Taxonomic Considerations
Common name: Ameba
Kingdom: Protista
Subkingdom: Protozoa
Phylum: Sarcomastigophora
Subphylum: Sarcodina (the amoebae)
Superclass: Rhizopoda
Class: Lobosea
Order: Amoebida
Family: Entamoebidae
Genus: Entamoeba
Species: histolytica

6. Geographical Distribution
Distribution is worldwide.
Higher incidence of Amoebiasis in
developing countries.
Parts of Africa and Asia endemic.

7. Prevalence
 Approximately 500 million people are
infected with E. histolytica worldwide.
 Almost 10% of the world population is
infected.
 Approximately affects 50 million persons
each year.
 Approximately 100 thousand die each
year, mostly from liver abscesses or other
complications.

8. Entamoeba histolytica
Habitats
Trophozoites of Entamoeba
histolytica live in the mucousa and
submucousa layers of large
intestine.

9. Entamoeba histolytica
Morphology
It has two stages:
a) Trophozoite.
b) Cyst.

10. Trophozoite:
– 15 - 30 m in diameter.
– single nucleus with
distinctive central karyosome.
– evenly distributed chromatin.
– the food vacuoles may contain
ingested RBCs.

11. Trophozoite (diagram)

12.  Cyst:
– mature: 4 nuclei.
– cigar-shaped chromatoid bodies.
– usually 10-20 m in diameter.
– the peripheral chromatin is evenly
distributed.
– the glycogen vacuoles stores food.
Quadrinucleate
Binucleate
Uninucleate

13.  Cyst(diagram)
• Cysts are susceptible
to heat (above 40 °C),
freezing (below –5 °C),
and drying.
• Cysts remain viable in
moist environment for
1 month or more.
Quadrinucleate
Binucleate
Uninucleate

14. Entamoeba histolytica Cysts
Uninucleate cyst Binucleate cyst

15. Entamoeba histolytica Cysts
Quadrinucleate or mature cysts

16. Entamoeba histolytica Life Cycle
• INFECTIVE STAGE:
Mature Cyst.

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

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

19. 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.

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

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

22. 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.

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

24. 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.

25. 10/14/2023 25

26. Disease: ranges from asymptomatic
(most common) to non-invasive diarrhea
(watery) to invasive, amoebic dysentery
(bloody, mucoid) to amoebic liver
abscess.
Infective stage: Mature cyst.
Diagnostic stage: Trophozoite & Cyst.
Transmission: direct fecal/oral route
(fecal contamination of food/ water & direct
with dirty hands).
Entamoeba histolytica

27. AMOEBIASIS
1. asymptomatic carrier state.
2. acute amoebic dysentery.
3. amoebic liver abscess.
4. Amoeboma.

28. Entamoeba histolytica
The disease may be:
o Intestinal infection.
o Extraintestinal infection:
causing liver, skin, lung
or brain abscesses.

29. E. histolytica cause a spectrum
of illnesses
 Intestinal disease
– Asymptomatic infection (carrier state)
– Symptomatic noninvasive infection
– Acute proctocolitis (dysentery)
– Toxic megacolon
– Chronic nondysenteric colitis
– Amoeboma
– Perianal ulceration

30. E. histolytica cause a spectrum
of illnesses
 Extraintestinal disease
– Liver abscess.
– Pleuropulmonary disease.
– Peritonitis.
– Pericarditis.
– Brain abscess.
– Genitourinary disease.

31. Symptoms
a) Intestinal amoebiasis
 Symptoms usually start within 1-4 weeks,
but the time between infection and
symptoms can be shorter and longer.
 Mild form of amoebiasis include watery
stools, abdominal pain, and stomach
cramps.
 Severe form of intestinal amoebiasis called
amebic dysentry followed by stomach
pain, bloody stools and fever.

32. b) Liver amoebiasis:
1. pain in hepatic region.
2. jaundice may be present.
3. edema of skin.
c) CNS amoebiasis:
Usually fatal due to late diagnosis.
Symptoms

33. • Ulcers with raised borders
• Little inflammation between lesions

34. • ‘Flasked-shaped ulcer’
• Trophozoites at boundary of necrotic
and healthy tissue
• Trophozoites ingesting host cells
• Dysentery (blood and mucus in feces)

35. ‘Haematophagous’ trophozoites

36. Amebic Liver Abscess
• Chocolate-colored ‘pus’
• necrotic material
• usually bacteria free
• Lesions expand and coalesce
• Further metastasis, direct
extension or fistula

37. Liver Abscess

38. Liver Abscess

39. Pulmonary Amebiasis
• Rarely primary
• Rupture of liver abscess through
diaphragm
• 2o bacterial infections common
• Fever, cough, pain, vomiting

40. Cutaneous Amebiasis
•Intestinal or hepatic fistula
•Mucosa bathed in fluids
containing trophozoites
•perianal ulcers
•urogenital (e.g., labia, vagina,
penis)

41. Diagnosis
Intestinal Disease
 Microscopic examination of stool for
demonstration of trophozoite and/or cyst.
• Cysts are usually seen in formed stools.
• Trophozoites are usually seen in diarrheic stools -
stools should be examined shortly after passage.
 At least three specimens of stool should be
examined.

42. Diagnosis
Intestinal Disease
 Sigmoidoscopy
• lesions, aspirate, biopsy.
 Antigen detection
• histolytica/dispar.

43. Diagnosis
Extraintestinal (hepatic) Disease
Imaging
• Computerized Tomography (CT).
• Ultrasound.
 Abscess aspiration
• only select cases.
• reddish brown liquid.
• trophozoites at abscess wall.

44. Diagnosis
Extraintestinal (hepatic) Disease
 Serology
• Only of value in confirming diagnosis
of invasive lesion.
• Current or past?
• ELISA
• Agar gel immunodiffusion
• Indirect immunofluorescence
Antibodies test (IFAT).

45. Sampling of liver abscess
Diagnosis

46. Treatment
a) Metronidazole (Flagyl)®.
b) Tinidazole (Fasigyn)®.
c) Tetracycline could also be used.
 Recent research indicate tinidazole much better
drug.

47.  Control is based on avoiding the
contamination of food or water with fecal
material.
 Drink only filtered or boiled water.
 Filtering water through "1 micron or
less" filter.
 Washing fresh fruit or vegetables by
clean water.
 Do not eat or drink milk, cheese, or dairy
products that may not have been
pasteurized.
Prevention and Control

48.  Do not eat or drink anything sold by
street vendors.
 Health education in regards to improving
personal hygiene.
 Sanitary disposal of feces.
Prevention and Control

49. Entamoeba coli
•Trophozoite:
•20-25 m.
•Nuclear structure:
•peripheral chromatin.
•Large karyosome.
•Cyst:
•15-25 m.
•8 nuclei (mature).
•pointed chromatoid
bodies.

50. Entamoeba coli
Trophozoite Cyst Nucleus

51. Entamoeba coli
• Life cycle and location identical to E. histolytica.

52. Entamoeba coli
• Life cycle and location identical to E. histolytica.
• Most common endocommensal in
people; has a worldwide distribution
and 10-50% of the population can be
infected in different parts of the world.

53. Entamoeba coli
• Life cycle and location identical to E. histolytica.
• Most common endocommensal in people; has a worldwide
distribution and 10-50% of the population can be infected
in different parts of the world.
• Not pathogenic.

54. Differences between
E. histolytica and E. coli
Entamoeba histolytica Entamoeba coli
Trophozoite
Nucleus Central karyosome .
Evenly distributed chromatin.
Eccentric karyosome.
Unevenly distributed
chromatin.
Cytoplasm May have ingested RBCs.
May have ingested bacteria, no
RBCs.
Motility Active, progressive motility. Sluggish motility.
Pathogenicity
Bloody diarrhea.
Colonic ulcer.
Abscess of liver, lung …ect.
Non pathogenic

55. Entamoeba histolytica Entamoeba coli
Cyst
Characteristics
Up to 4 nuclei.
Cigar-shape chromatoid
bars.
Up to 8 nuclei.
Chromatoid bars with
cracked ends.
Differences between
E. histolytica and E. coli

56. Intestinal Amebae

57. Nuclear Morphology

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