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Ameba: Formally Phylum Sarcodina
R & 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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(gel-like)
(more fluid)
Complex changes in cell
fine structure, chemistry,
and behavior.
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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 commoninhabitants of animals.
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Endocommensal and Parasitic
Ameba Diversity Domestic animals
Birds are free
Reptiles one species that is pathogenicin snakesEntamoeba 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 isprimarily a human parasite and is transmitted from human to
human.
First seen in 1878 but not described until1903.
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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 isprimarily a human parasite and is transmitted from human tohuman.
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 bluntpseudopodia
Non-foamy cytoplasm
Uninucleated; nucleuswith fine peripheral
chromatin granules,
small central endosomeTrophozoite: 20-30 m
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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
Cyst:10-20 m
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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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INFECTIVE STAGE: Cyst
Entamoeba histolytica Life Cycle
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INFECTIVE STAGE: Cyst
Cysts are susceptible to heat (above 40
C), freezing (below5 C), and drying.
Entamoeba histolytica Life Cycle
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INFECTIVE STAGE: Cyst
Cysts are susceptible to heat (above 40 C), freezing
(below5 C), and drying. Cysts remain viable in moist environment
for 1 month.
Entamoeba histolytica Life Cycle
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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 smallintestine in an alkaline environment.
Metacystic amebas
emerge, divide and movedown 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 mucosafeeding 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 cellsand 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 largeintestine to liver via hepatic
portal vein.
Liver Abscesses
b hi l i P h l
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Entamoeba histolytica Pathology
2. Extra-Intestinal
Lesions and AbscessOccurs
E b hi l i P h l
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Entamoeba histolytica Pathology
2. Extra-Intestinal
Lesions and AbscessOccurs
A. Hepatic Amebiasis
E b hi l i P h l
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Entamoeba histolytica Pathology
2. Extra-Intestinal
Lesions and AbscessOccurs
A. Hepatic Amebiasis
B. Pulmonary Amebiasis
E b hi l i P th l
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Entamoeba histolytica Pathology
2. Extra-Intestinal
Lesions and AbscessOccurs
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 didnot 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 worldwidedistribution but is most common in the tropical and
subtropical areas of the world.
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Entamoeba histolytica
DISTRIBUTION - Parasite has worldwidedistribution 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 worldwidedistribution 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: < 1% in Canada and Alaska0.9% in U.S.
40% in the tropics
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Entamoeba histolytica
A number of outbreaks have resultedfrom a breakdown in sanitation or
behavioral practices of people.
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Entamoeba histolytica
A number of outbreaks have resulted from a breakdown insanitation 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 insanitation 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 ofamebiasis resulting in 58 deaths.
Outbreak in the late 1970s in New York
City among gay men.
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