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Other Human Amoebae
• Entamoeba dispar/E. hartmanni: Non
pathogenic; anatomically
indistinguishable from E. histolytica.
Entamoeba coli
Trophozoite
Cyst
Nucleus
Entamoeba coli
• Life cycle and location identical to E. histolytica.
Entamoeba coli
• Life cycle and location identical to E. histolytica.
• Most common endocommensal in people; has a
worldwide distribution and 10-50% of the
population can be infected in different parts of the
world.
Entamoeba coli
• Life cycle and location identical to E. histolytica.
• Most common endocommensal in people; has a worldwide
distribution and 10-50% of the population can be infected
in different parts of the world.
• Not pathogenic.
Entamoeba coli
• Life cycle and location identical to E. histolytica.
• Most common endocommensal in people; has a worldwide
distribution and 10-50% of the population can be infected
in different parts of the world.
• Not pathogenic.
• Feeds on bacteria and any other cells available
to it; does not invade tissue.
Other Hosts
Monkeys
Apes
Pigs
10 mm
Trophozoites 20-30 μm in
diameter (15-50 µm)
A
B
C
10 mm
D
E. coli
A
B
E. histolytica
C
10 mm
D
C
Cysts 10-30 μm
10 mm
Entamoeba gingivalis
Habitat: Mouth
Hosts: Humans, other primates,
dogs and cats.
Prevalence is from 50 to 95%.
Stage: Trophozoite, no cyst.
Entamoeba gingivalis
Trophozoite lives on the surface of teeth and gums.
Feed on epithelial cells of the mouth, bacteria, food
debris, and other cells available to them.
Entamoeba gingivalis
Trophozoite lives on the surface of teeth and gums. 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.
Entamoeba gingivalis
Trophozoite lives on the surface of teeth and gums. 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 mouth to mouth, droplet spray, or
sharing eating utensils.
Endolimax nana “The dwarf internal slug”
Trophozoite
Cyst
Nucleus
Endolimax nana
• Second most common endocommensal of
humans, worldwide distribution 30%.
Endolimax nana
• Second most common endocommensal of humans,
worldwide distribution 30%.
• Lives in the large intestine mainly near
the cecum and feed on bacteria; non
pathogenic.
Endolimax nana
• Second most common endocommensal of humans,
worldwide distribution 30%.
• Lives in the large intestine mainly near the cecum and
feed on bacteria; non pathogenic.
• Also occurs in monkeys.
Trophozoites are tiny
6-15 μm in diameter.
Large glycogen
vacuoles are often
present.
10 mm
Mature cyst is 5 – 14
μm in diameter;
contains 4 nuclei;
shape is round to
elliptical
10 mm
Iodamoeba buetschlii
Trophozoite
Cyst
Nucleus
Iodamoeba buetschlii
• Not very common endocommensal in
people.
Iodamoeba buetschlii
• Not very common endocommensal in people.
• Lives in the large intestine,
predominantly in the cecal areas.
Iodamoeba buetschlii
• Not very common endocommensal in people.
• Lives in the large intestine, predominantly in the cecal
areas.
• Has a very high prevalence in pigs; 50%
of pigs are infected with this ameba in
France and Egypt; pigs are probably its
normal host.
10 mm
Trophozoites are 914 μm long but may
be as large as 20μm
10 mm
E. nana
10 mm
I. buetschlii
Cysts are 6-15 µm
long and have a
large glycogen
vacuole.
10 mm
Dientamoeba fragilis
Trophozoite
No Cyst
Nucleus
Dientamoeba fragilis
• LIFE CYCLE - it does not form cysts
and trophozoites cannot survive passage
through the small intestine.
Dientamoeba fragilis
• LIFE CYCLE - it does not form cysts and trophozoites
cannot survive passage through the small intestine.
• Humans probably get infected by this
endocommensal when they ingest
pinworm eggs!
Trophozoites small
6-12 µm long;
binucleated.
10 mm