Ameba: Formally Phylum Sarcodina R & J Ch 7

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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.

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Ameboid Movement

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

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Complex changes in cell fine structure,
chemistry, and behavior.
(gel-like)
(more fluid)
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Mechanisms of Ameboid Movement
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Mechanisms of Ameboid Movement
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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.

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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

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Some Ameba are Pathogenic

• Amebiasis- The pathological condition of having
  an amoebic infection.
• -iasis- indicates a pathological condition

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Entamoeba histolytica
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Entamoeba histolytica

• One of the most important and pathogenic
  parasites of humans.

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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.

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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.

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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).

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Entamoeba histolytica
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Entamoeba histolytica

• Active, feeding stage
• Growing stage
• Amoeboid with blunt pseudopodia
• Non-foamy cytoplasm
• Uninucleated nucleus with fine peripheral
  chromatin granules, small central endosome

Trophozoite 20-30 µm
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Entamoeba histolytica Trophozoites
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Entamoeba histolytica

• Dormant/resistant stage
• Spherical
• 1-4 nuclei, (4 in mature cysts)
• Bluntly rounded chromatoidal bars

Cyst10-20 µm
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Entamoeba histolytica Cysts
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Entamoeba histolytica Cysts
Uninucleate cyst Binucleate
cyst
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Entamoeba histolytica Cysts
Quadrinucleate or mature cysts
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Entamoeba histolytica Life Cycle
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Entamoeba histolytica Life Cycle

• INFECTIVE STAGE Cyst

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Entamoeba histolytica Life Cycle

• INFECTIVE STAGE Cyst
• Cysts are susceptible to heat (above 40 C),
  freezing (below 5 C), and drying.

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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.

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Entamoeba histolytica Life Cycle

• CYST ingested with fecal contaminated food or
  water.

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Entamoeba histolytica Life Cycle

• CYST ingested with fecal contaminated food or
  water.
• Excystation occurs in the small intestine in an
  alkaline environment.

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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.

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Entamoeba histolytica Life Cycle

• Trophozoites colonize the large intestine and
  invade the mucosa.

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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.

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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.

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Entamoeba histolytica Life Cycle

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

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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.

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Entamoeba histolytica

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

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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.

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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.

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Entamoeba histolytica Pathology
1. A Primary Ulcer Can Occur.
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Entamoeba histolytica Pathology
1. A Primary Ulcer Can Occur.
Flask Shaped Ulcers
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Entamoeba histolytica Pathology
1. A Primary Ulcer Can Occur.
A primary ulcer can cause rupturing of the bowel
and can cause Peritonitis.
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Shows movement of trophozoites from large
intestine to liver via hepatic portal vein.
Liver Abscesses
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Entamoeba histolytica Pathology

• Extra-Intestinal Lesions and Abscess Occurs

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Entamoeba histolytica Pathology

• Extra-Intestinal Lesions and Abscess Occurs
• A. Hepatic Amebiasis

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Entamoeba histolytica Pathology

• Extra-Intestinal Lesions and Abscess Occurs
• A. Hepatic Amebiasis
• B. Pulmonary Amebiasis

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Entamoeba histolytica Pathology

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

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Entamoeba histolytica Pathology

• Frequently, intestinal lesions will heal
  themselves.

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Entamoeba histolytica Pathology

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

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Amoebic Amebiasis of the Skin
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Symptoms

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

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Symptoms

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

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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.

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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.

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So How Bad is This?

• In theory, ingestion of 1 cyst could kill you.
• In practice, probably it will never happen.

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Prognosis

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

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Diagnosis

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

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Seriousness of Diagnosis

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

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Treatment

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

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Epidemiology

• How an infectious organism spreads through a
  population.

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Entamoeba histolytica
DISTRIBUTION - Parasite has worldwide
distribution but is most common in the tropical
and subtropical areas of the world.
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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.
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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. PREVALENCE lt 1 in Canada and Alaska
0.9 in U.S.
40 in the tropics
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Entamoeba histolytica

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

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Entamoeba histolytica

• A number of outbreaks have resulted from a
  breakdown in sanitation or behavioral practices
  of people.
• Outbreak in 1933 World's Fair in Chicago caused
  by defective plumbing (cross connections between
  water lines and sewer lines) caused over 1,000
  cases of amebiasis resulting in 58 deaths.

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Entamoeba histolytica

• A number of outbreaks have resulted from a
  breakdown in sanitation or behavioral practices
  of people.
• Outbreak in 1933 World's Fair in Chicago caused
  by defective plumbing (cross connections between
  water lines and sewer lines) caused over 1,000
  cases of amebiasis resulting in 58 deaths.
• Outbreak in the late 1970s in New York City
  among gay men.