The Amebae Chapter 7

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The Amebae Chapter 7
Old taxonomy Phylum Sarcomastigophora
Subphylum Sarcodina New taxonomy Phylum
Sarcodina or Super-Group Amebozoa Amebae
move and feed through the ______________________
_____________________________ Some amebae may
have a __________________________as well in their
life cycle (indicates evolution from the
Mastigophora). Most amebae are free-living
organisms in soil and water. A few species have
become parasitic in vertebrates and may cause
dangerous diseases in their hosts.  
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2 Groups of Parasitic Amebae
____________________parasites can only exist as
parasites - amebae in the family Entamoebidae -
occur in the digestive tracts of
vertebrates ____________________parasites
free-living soil and water amebae that can become
parasitic if they enter vertebrate tissues
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Obligatory Amebae Family Entamoebidae
Entamoeba histolytica

• One of the most important and pathogenic
  parasites of humans
• Although pigs and primates may be infected,
  these infections are rare and unimportant. This
  parasite is transmitted from human to human
  thus, this parasite is an ________________________
  _____________
• First seen in 1878 but not described until 1903
• Causative agent of the disease ___________________
  ________ (old name is Amebic Dysentery)

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Entamoeba histolytica
DISTRIBUTION - Parasite has worldwide
distribution but is most common in the
___________________________________of the
world  - it is estimated that up to 500 million
people may be affected  - may cause up to 100,000
deaths each year  - a number of outbreaks have
resulted from a breakdown in sanitation
Outbreak in 1933 World's Fair in Chicago caused
by defective plumbing (cross connections between
water lines and sewer lines) caused over 1000
cases of amebiasis resulting in 58
deaths   PREVALENCE _________ in Canada and
Alaska _________ in U.S.
(________ in Wisconsin in 1987)
_________ in the tropics
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Entamoeba histolytica 2 stages

• 1. TROPHOZOITE - 20 to 30 µm in diameter
  stained specimens ____________
•  - cytoplasm consists of clear ectoplasm, finely
  granular endoplasm food vacuoles often
  containing rbc's are common
• characteristic structure is the single nucleus
  with one endosome
• __________________________________________________
  ___
• __________________________________________________
  ___
• living specimens show active,
  
  rapid movement
• primary habitat of the trophozoites
  
  is the ___________________________
  
  (but can metastasize to other organs)

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Entamoeba histolytica trophozoites
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Entamoeba histolytica 2 stages
2. CYST - encystment is stimulated by
________________________________ -
trophozoite condenses into a sphere - the
_________________________ - precyst
secretes cyst wall to form the round cyst - 10 to
20 ?m in diameter - nuclear division begins
after encystment _______________ cyst ?
________________cyst ? _________________

or mature cyst
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Entamoeba histolytica cysts

• Cyst nuclei possess even peripheral chromatin and
  a central endosome (endosome position may be
  off-center in some stained specimens)
• cytoplasm contains rod-shaped ___________________
  __________________ - cigar-shaped areas of
  packaged _______________ - and vacuoles
• chromatoidal bars and vacuoles are most common
  in young cysts (uninucleate
  binucleate). In mature cysts, ____________________
  _________

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Entamoeba histolytica cysts
uninucleate cyst
binucleate cyst
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Entamoeba histolytica mature cysts
quadrinucleate or mature cysts diagnostic
in feces
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Entamoeba histolytica life cycle
DIAGNOSTIC STAGE  INFECTIVE STAGE 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
Infection occurs when infective cysts are
ingested in food or water that has been
contaminated with human feces. Thus, this
parasite is transmitted from human to human via
fecal contamination and is an ____________________
__  
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Entamoeba histolytica life cycle
Common source of infection is from the use of
________________________ - _____________________
used to fertilize vegetables  
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Entamoeba histolytica life cycle
.
Excystment Metacystic ameba undergoes
multiple fission to form _____ trophozoites. Troph
ozoites move into the large intestine and invade
the mucosa.
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Entamoeba histolytica pathology
1. COLONIZATION OF THE LARGE INTESTINE flask-sha
ped lesions proteolytic enzymes
Symptoms Ulcers may form sinuses and
extend into the submucosa  
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Entamoeba histolytica pathology
1. COLONIZATION OF THE LARGE INTESTINE primary
ulcer  
Mucosa submucosa
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Entamoeba histolytica pathology
2. COMPLICATIONS IN LARGE INTESTINE
 A. Ulcers extend deep into the
_______________________________and may extend
completely through the large intestine causing a
_______________________________
_______________________________________(bacterial
infection in the abdominal cavity) - this
complication results in a high percentage of
fatalities   B. Trophozoites invade the blood
vessels of the submucosa and metastasize to
ectopic sites
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Entamoeba histolytica pathology
3. EXTRA-INTESTINAL LESIONS occur in 3 ECTOPIC
SITES A. HEPATIC AMEBIASIS
Trophozoites in submucosa are carried by hepatic
portal vein to the liver. Trophozoites
digest away liver tissue forming
_________________________ - some to size of
grapefruit B. PULMONARY AMEBIASIS
Liver abscess ruptures Trophozoites
digest through the ______________________into
the lungs to form a__________________
____________ C. CEREBRAL AMEBIASIS Trophozoites
in bloodstream reach ________________________
form fatal _________________________
 
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Diagram of pathology from text on page 112 Shows
movement of trophozoites from large intestine to
lungs via hepatic portal vein
Liver abscess
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Diagnosis and Treatment of Entamoeba histolytica

• DIAGNOSIS microscopic identification of cysts
  and trophozoites in fecal samples
• Differentiation of E. histolytica from other
  non-pathogenic amebae is important.
• Why?
•  
• TREATMENT _______________________________
  antibiotics are effective against large
  intestinal forms
• Treatment difficult once ectopic sites are
  invaded

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Non-pathogenic Amebae
We will examine 3 species in laboratory
Entamoeba coli 
Very common parasite in the
__________________________________________________
__________________________________________________
__ Often co-exists with E. histolytica but
is_______________________________________ Cosmopol
itan in its distribution Prevalence in U.S. is
estimated at _________ prevalence in tropics
may be up to 100
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Entamoeba coli life cycle stages
1. TROPHOZOITE - 20 to 30 ?m in diameter  -
granular endoplasm is coarser than E.
histolytica   - structure of nucleus
____________________________________________ _____
__________________________________________________
_________ - lives in large intestine and
feeds on bacteria and any other cells available
to it does not invade
tissue
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Entamoeba coli life cycle stages
2. CYST - encystment is similar to that of
E. histolytica - immature cysts are rare in
fecal smears - mature cyst is large, 10 to 33
?m, has _____ nuclei - chromatoidal
bodies, if present, have splinter-like ends
(disappear in most cysts) - cyst is released in
the feces into the external environment -
importance of human infection?
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Entamoeba coli life cycle
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Endolimax nana
Non-pathogenic parasite in the ___________________
____________________________________________
Cosmopolitan - __________ prevalence in the
world  
2 stages in the life cycle 1. TROPHOZOITE -
small in size 6 - 15 µm (usually under 10 ?m)
- structure of nucleus   - moves slowly
feeds on bacteria and food debris  
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Endolimax nana
2. CYST - forms as feces dehydrates 
- small in size (5 - 14 ?m) - contains
____ nuclei with large endosomes   - importance
of human infection
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Endolimax nana life cycle

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Iodamoeba bütschlii I. buetschlii
Parasite in the __________________________________
_________________  Non-pathogenic Cosmopolitan
in distribution Prevalence in world is
___________ (much less than E. coli Endolimax)

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Iodamoeba bütschlii I. buetschlii
1. TROPHOZOITE - 9 to 20 ?m in diameter   -
structure of nucleus   - feed on
bacteria and yeast do not invade tissue

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Iodamoeba bütschlii I. buetschlii
2. CYST - 6 to 15 ?m in diameter -
________________ nucleus with large endosome and
lightly-stained granules - large
___________________________(appears clear) in
cytoplasm - stains deeply with iodine
hence, the genus name Method of human
transmission

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Iodamoeba bütschlii life cycle

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3 Other Non-Pathogenic Amebae (we will not
examine these in lab)
Entamoeba hartmanni Originally thought to be a
"small race" of E. histolytica, it is now
considered to be a
separate species. The morphology of E. hartmanni
is nearly identical to E. histolytica
except it is SMALLER
IN SIZE  - trophozoites are typically 12 - 15 ?m
in diameter    - nuclear structure is
similar (endosome in center) but peripheral
chromatin is more irregular   - cysts are 5
- 9 ?m in diameter and contain 4
nuclei Pathology Importance
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Entamoeba dispar

• 1993 E. dispar was proposed as the name for
  non-pathogenic E. histolytica.
• Substantial biochemical and molecular data has
  been accumulated showing that the non-pathogenic
  isolates of E. histolytica are genetically
  distinct from the pathogenic isolates
• Identical to E. histolytica but does not invade
  tissue so is non-pathogenic.
• _________________________________

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Entamoeba gingivalis
  Habatit Hosts Prevalence is from
50 to 95.   Stage Trophozoite lives on
the surface of teeth and gums. Parasites feed on
epithelial cells of the mouth, bacteria, food
debris, and other cells available to them.
Organisms are more common in persons with
pyorrhea (gum disease) but they are not the cause
of the condition. Transmission  
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Facultative Amebae
Facultative amebae are normal inhabitants of soil
and water where they feed on bacteria. A few
members have the ability to become parasitic when
an opportunity to enter a vertebrate
exists. Three are able to infect
humans Naegleria fowleri This ameba is
responsible for over 200 cases of
__________________________________________________
___ During 1989-2000, CDC documented 24 fatal
cases of PAM in the United States. Only 7 cases
were successfully treated all others were fatal!
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Naegleria fowleri
Trophozoites can occur as an ameboid form or a
flagellated form in freshwater. Parasite can
form a cyst in dry periods. Flagellated
trophozoites enter the nasal passages when a
victim swims or dives into freshwater. All
victims have had a history of ____________________
__________________________________________________
_________________a few days before the onset of
symptoms
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Naegleria fowleri
Once it enters a human, the parasites always
revert to the ameboid form. - contains
____________________________________ - usually
forms ____________________________________
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Naegleria fowleri pathology
After entering the nose and nasal cavities, the
trophozoites migrate along the ___________________
________ to the _________________________ Ameboid
trophozoites multiply rapidly by binary fission
in the brain and cause ___________________________
________ Symptoms include a headache, fever, neck
rigidity, and mental confusion followed by coma
and death Death usually occurs in
___________________________  
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Naegleria fowleri

• DIAGNOSIS most cases have been diagnosed at
  _____________________by identification of large
  numbers of amebae in the brain tissues
• Look for trophozoites each with a nucleus with
  _____________________________
• - Disease is so rare and the brain tissue
  destruction is so rapid that diagnosis is seldom
  made in time

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Naegleria fowleri
TREATMENT the drug __________________________
has been successful in the treatment of
only 7 cases DISTRIBUTION - Most cases of this
disease have been in the _____________________
U.S. (see case reports in lab). Cases have also
been described in Europe, Africa, and
Australia. In Wisconsin?
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Acanthamoeba spp.

• At least 5 species of Acanthamoeba have been
  identified in human tissues.
• Free-living trophozoites and cysts occur in both
  the soil and freshwater.
• Trophozoites occur only as ameboid forms
• structure

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Acanthamoeba spp. pathology

• These species cause 2 pathological effects
  
• Over 100 cases of granulomatous amebic
  meningoencephalitis caused by Acanthamoeba have
  been documented
• Disease was much more chronic in infected
  patients, all of which were ______________________
  ____________
• Most, however, resulted in death in a few
  months.
• Mode of transmission is not known, as no history
  of swimming occurred in some
  cases.
• Possibility?

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Acanthamoeba spp. pathology
(2) I ncriminated in a number of cases of
__________________________ (inflammation and
opacity of the cornea). Most of these
ocular infections were in contact lens wearers
who used home-made saline   It appears that a
____________________
or swimming with
contact lenses were
necessary for invasion
Diagnosis by identifying amebae

in corneal scrapings Drug treatment has
been successful
in most cases
Several cases have been reported in
Wisconsin -
see case reports in lab  
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New faculative ameba recently identified

• A new freshwater ameba called Balamuthia has been
  incriminated is some 80 cases of amebic
  meningoencephalitis in humans since 2001.
• only 2 survivals
• most reports from ______________
• easily misidentified so some of
  the cases of
  granulomatous amebic
  meningoencephalitis caused by
  Acanthamoeba may well have
  been
  caused by Balamuthia