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”
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).
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.
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.
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
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.
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.
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.
