Ameba: Formally Phylum Sarcodina R & J Ch 7

2. Ameba: Formally Phylum SarcodinaR & J Ch 7 • 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.

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

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

6. Mechanisms of Ameboid Movement

7. Mechanisms of Ameboid Movement

8. 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.

9. 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

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

11. Entamoeba histolytica

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

13. 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.

14. 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.

15. 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).

16. Entamoeba histolytica

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

18. Entamoeba histolytica Trophozoites

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

20. Entamoeba histolytica Cysts

21. Entamoeba histolytica Cysts Uninucleate cyst Binucleate cyst

22. Entamoeba histolytica Cysts Quadrinucleate or mature cysts

23. Entamoeba histolytica Life Cycle

24. Entamoeba histolytica Life Cycle • INFECTIVE STAGE: Cyst

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

26. 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.

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

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

29. 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. Entamoeba histolytica Life Cycle

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

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

32. 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. Entamoeba histolytica Life Cycle

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

34. 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.

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

36. 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.

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. • However, when the host is stressed, has too much HCl, or a high bacterial flora, the digestion will be ahead of repair.

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

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

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

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

42. Entamoeba histolytica Pathology • Extra-Intestinal Lesions and Abscess Occurs

43. Entamoeba histolytica Pathology • Extra-Intestinal Lesions and Abscess Occurs • A. Hepatic Amebiasis

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

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

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

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

48. Amoebic Amebiasis of the Skin

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

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