This document describes several non-pathogenic and pathogenic amoeba species. It discusses their characteristics such as habitat, morphology of trophozoite and cyst stages, transmission methods, and prevalence in humans. Some notable amoeba discussed are Entamoeba coli and Entamoeba histolytica which are common gut commensals, as well as Naegleria fowleri and Acanthamoeba species which can cause infections in humans and are typically found in soil and water environments. The document provides detailed information on the life cycles, symptoms, and diagnosis of diseases caused by these pathogenic free-living amoeba.

1. Non- pathogenic amoebae:
 E. dispar.
 E. hartmanni.
 E. coli.
 E. gingivalis.
 E. nana.
 I. butschlii.

2. E. dispar:
 Non-invasive, non pathogenic.
 Earlier it was considered as non pathogenic strain of E.
histolytica.
 E. histolytica and E. dispar are morphologically identical.
 Cyst of E. histolytica and E. dispar can not be differentiated
microscopically.
 Has a prevalence rate of 10 – 30% worldwide.

3. E. coli:
 World wide parasite, Has a prevalence rate of 10 – 30%.
 Habitat lumen of large intestine of man (Gut commensalism).
 It exist in 3 stages trophozoite, pre-cyst and cyst.
 Slow (lazy) movement.
 Oral-fecal transmission.
 Life cycle similar to E. histolytica.

4. Trophozoite:
 The trophozoite is 15- 50
µm, sluggish in movement.
 It has a more granular
endoplasm containing food
vacuoles, ingested bacteria,
depress, a narrow ectoplasm
and a large karyosome.
 Nuclear membrane is thick
and is lined by coarse
chromatin granules.

5. Cyst:
 The cyst is spherical and
usually larger than that of
E. histolytica. Its size is 10-
31 µm and has 8 nuclei
 Chromatoid body is
filamentous.
 Pre-cyst resemble in shape
with that of E. histolytica.

6. :
E. hartmanni
 Described by Burrows.
 It is similar to E. histolytica and previously considered as
small race of it.
 Trophozoite and cyst are smaller and have a diameter of 4- 12
µm and 5- 10 µm respectively.
 Trophozoite never contain ingested red blood cells.
 Life cycle similar to E. histolytica.
 Lab diagnosis is by measurement of size of the trophozoite
and cyst and absence of red blood cells in trophic stage.

7. Trophozoite:
 Is 4- 12 µm without red blood cells and less rapid motility
than E. histolytica.

8. :
Cyst
 Is 5- 10 µm with 1- 4 nuclei and chromatoid body.

9. E. gingivalis:
 The first amoeba of man to described (Gros in 1849).
 Only trophozoite stage have been found.
 It live in gingival tissue between teeth and gum.
 It transmitted by oral contact (closely contact like kissing and
from contaminated utensils.
 Its prevalence rate rang between 10% in person with healthy
mouth to 95% in those with diseased teeth and gum.
 Also found in the diseased tonsils and in the vaginal and
cervical smear from women using intrauterine devices.

10. Trophozoite:  Measure 5- 25 µm.
 Actively motile by
multiple pseudopodia
 The food vacuole contain
leukocyte, epithelial cell
and red blood cells.
 Nucleus spherical,
central karyosome.
 Chromatin granules are
closely packed.

11. Endolimax. nana:
 Firstly described by Wenyon and O’Connor. It has a
prevalence of 10 - 20% throughout the world.
 Habitat lumen of large intestine of man, primates and pigs.
 It has 3 stages trophozoite, pre-cyst and cyst.
 Trophozoite is small in size 6- 15µm in diameter, with a
granular, vacuolated cytoplasm , central nucleus and a
sluggish movement.
 Chromidial pars and glycogen vacuole are absent.
 The cyst is oval in shape, ranging from 5- 14 µm in diameter,
with 4 indistinct nuclei and no chromatoid bars.

12. Trophozoite Cyst

13. I. butschii:
 The term Iodamoeba mean an amoebae that stain well with
iodine.
 Un like other intestinal amoebae, the nucleus does not undergo
typical division. It resembling basket of flowers in shape
 It is not as common as E. coli or E. nana. It was discovered by
Dobell and its prevalence rate is about 8%.
 The trophozoite is 6- 25 µm with progressive movement in
fresh stool. The cytoplasm has food vacuole (bacteria and
yeast cells).
 The cyst is irregular in size, measuring 6- 15 µm in diameter,
has one nucleus and a large glycogen vacuole. (Iodine cyst).
 Chromidial pars are absent.

14. Iodine cyst

15. D. fragilis:
 Probably transmitted person to person protected inside the ova
of pin worm.
 It is a small parasitic amoeboflagellate found only as a
trophozoite in fresh liquid or soft stools .
 It is small in size with two nuclei and circular appearance at
rest. Numerous granules are present in the cytoplasm and
exhibit Brownian motion this known as Hakansson
phenomenon and it is diagnostic feature for identification. It
has a rapid action and disintegrates in water.
 It may ingest red blood cells and its prevalence is 4%.

16. Trophozoite:

17. Free-living amoebae causing human infection:
 Are normal inhabitants of soil and water there they feed on
bacteria.
 A few members have the ability to become facultative
parasites when an opportunity to enter a vertebrate exists.
 These are able to infect human;
 Naegleria fowleri.
 Acanthameoba species.

18. Naegleria fowleri:
 It is free-living brain eating amoeba.
 Typically found in a warm fresh water (thermo tolerant
amoeba).
 World wide distribution.
 It exist in trophozoite and cyst forms and in transient flagellate
stage.
 It is causative agent of primary amoebic meningoencephalitis.
 The incubation period is short, the symptoms are acute and
death is almost certain and rapid.
 When a victim swims or sinks into freshwater.
 All victims had a history of swimming in freshwater lakes or
ponds or swimming pools a few days before the onset of
symptoms.

19.  It invades the CNS via penetration of the olfactory mucosa and
nasal tissues.
 When a victim swims or sinks into freshwater.
 All victims had a history of swimming in freshwater lakes or
ponds or swimming pools a few days before the onset of
symptoms.
 Most symptoms involving fever, headache, stiff neck and
confusion.
 Diagnosis with X-ray. IHAT in CSF.
 Occasionally a CT scan may be ordered to rule out cerebral
hematoma. Culture media of CSF and PCR.
 Since the parasite is susceptible to chlorine, swimming pools
should be adequately chlorinated.

20. Trophozoite:
 The trophozoite is
elongated in form, 10- 27
µm, rapidly motile,
vacuole can be seen in
the cytoplasm.
 Do not ingested RBCs .

21. Acanthameoba species:
 Free-living trophozoite and cyst occurs in both soil and
freshwater, sea water, sewage, swimming pools, contact lens,
equipment, medicinal pools, dental treatment units and air
conditioning systems..
 Trophozoite occurs only as amoeboid forms.
 Cyst is common and very resistant to chlorine.
 Causing ulceration of skin and infection of other tissue in
HIV person.
 Contact lens wearers can get keratitis (infection of the cornea)
by using tap water for lens disinfection or by swimming when
wearing lenses.

22.  It causes three clinical syndromes:
 Granulomatous amoebic encephalitis (mental status, headache
fever, neck stiffness, seizures, focal neurological signs and
coma leading to death).
 Disseminated granulomatous amoebic disease (skin, sinus and
pulmonary infections).
 Amoebic keratitis a sight threatening disease, most cases
occur in people who wear contact lenses.
 Diagnosis of keratitis; the trophozoites or cysts can be
demonstrated with corneal scraping or biopsy sample via wet
mount, stains or histopathologic examination.
 Granulomatous amoebic encephalitis; this condition is
diagnosed via brain biopsy.