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1. Pathogenic Free-Living Amebae

2. Objectives
After taking this unit the student will be able to:
1. list common Pathogenic free living amoeba
2. Identify the common characteristics of Pathogenic
free living amoeba
3. Discuses the epidemiology, life cycle,
pathology.laboratory diagnosis and clinical aspects
of Naegleria fowleri and Acanthamoeba spp

3. Outline
Naegleria fowleri and Acanthamoeba spp
– General feature of pathogenic free living amoeba
– Epidemiology
– Morphology
– Transmission and life cycle
– Pathology and clinical manifestation
– Laboratory diagnosis

4. Pathogenic Free-Living Amebae
• Naegleria fowleri
• Acanthamoeba spp
• Balamuthia mandrillaries
• Sappinia diploidea

5. General characteristics
• Usually free living
• Rarely infect humans
• Acquired by soil/water contact
• No human to human or vector borne
transmission
• Causes Acute/chronic amebic
meningoencephalitis

6. Distribution: worldwide
Habitat: Free living
Fresh water/lakes and ponds
Moist soil
Parasitic
Nasal cavity and CNS
Causes: primary amebic meningoencephalitis
(PAM)
PAM first recognized by Fowler (1965)
~ 200 documented cases worldwide
Naegleria fowleri

7. low nutrients
Distilled water
desiccation
Morphology & Life cycle
Amoebofllagelate
Cyst = dormant form
Amoebid
Trophozoite =
Flagellate =
feeding and
replicating form
None feeding
Don’t replicate
•Feed on bacteria &
organic matter
•Enter nose-Infect
brain via olfactory
nerve
For dispersal in
evt.
Nutrients
restored

8. All stages are characterised by:-
-Single neuclus
-Large kariyosome
-No peripheral chromatin granules

9. Transmission
• Infection:- through nasal cavity by
aspiration of water contaminated with
trophozoites while;-
• bathing in stagnant fresh water/lakes/pools
contaminated with sewage/decaying matte
• under chlorinated swimming pool
• Snuffing water from lakes/ponds etc

11. Life Cycle of Naegleria fowleri
Amoeba form in
water
Cyst
Binary
Fission
Inhaled in
water
Flagellate
form
Change to
Amoeba
Travels along olfactory
nerves
Amoeba in
brain

12. pathology
• Causes Primary Amebic Meningoencephalitis (PAM)
• symptoms usually within a few days after
swimming in warm still waters(1-14 days)
• symptoms include headache, lethargy,
disorientation, coma
• rapid clinical course, death in 4-5 days after onset
of symptoms
• trophozoites can be detected in spinal fluid, but
diagnosis is usually at autopsy

13. N. fowleri: Pathology
• Causes Primary Amebic
Meningoencephalitis
(PAM)
• Very rapidly causes the
death of host
– Rapid destruction of
brain tissue

16. N. fowleri: Symptoms
Symptoms very similar to other types of meningitis and
encephalitis.
• Symptoms usually within a few days after swimming
in warm still waters(1-14 days)
• Symptoms include headache, lethargy, disorientation,
coma
• Rapid clinical course, death in 4-5 days after onset of
symptoms
• But much less common and usually mistaken for more
common bacterial and viral forms

17. N. fowleri: Laboratory diagnosis
• Diagnosis is usually
made at autopsy.
– Amoeba in a brain smear
• May be possible to
diagnose with spinal tap.

18. Laboratory diagnosis
• Finding trophozoites in CSF
CSF: purulent & may contain eosinophils,
RBC with reduced glucose and
raised protein
-Indications of Naelgeria infection:
elevated white cell count in CSF
without the successful recovery of bacteria

19. Naegleria trophozoites
• Elongate in form, 10-22x7 micro
m in size
• Rapidly motile(>2body
length/minute
• Psuedopodia are lobulate or
explosive protrution
• No RBC ingested
• One or more contractile vacuoles
• Remain motile for several hrs
• Can be stained by giemsa or
acridine orange
“lobopodia”

20. Masses of amoeba may be seen histopathologically in the
brain

21. N. fowleri: Treatment
• Treatment is rarely given
– Amphotericin B has been used successfully in
two human cases.
• Very toxic
– A traditional treatment is qinghaosu
• A plant that also fights malaria
• Prevention
– Keep head above water (or use nose plugs) in
thermal pools or other warm, stagnant water.

22. N. fowleri: Summary
• N. fowleri found in water everywhere but
very rarely causes infection.
• Cannot penetrate any opening other than
nasal passages
• No other species in the genus Naegleria
cause PAM.
– Experimentally infected lab animals with all
species of Naegleria
– Only N. fowleri caused infection.

23. Acanthameoba sp.
• Definitive Host: Usually
Free-living
– Facultative parasite of humans
• Intermediate Host: None
• Geographic Distribution:
Cosmopolitan
– Found in freshwater almost
everywhere
• Amoeba and cyst forms
– Cannot survive in thermal
pools

24. Acanthameoba sp.
• Mode of transmission:.
– Cyst and trophozotes are infective
– portal of entry unknown, possibly respiratory tract
(inhalation of cysts)
– invades body through cuts and abrasions or
wounds in skin/eye contaminated with soil
– The brain is probably infected by trophozoites via
blood stream from infected skin or lung
• Location in Host: Most common in eye and skin.
Rarely invades brain/lung

25. Morphology & life cycle
Typical protozoan life cycle
Exist as trophozoites and Cyst
cyst & trophozoit are
infective
Angular in shape with
three layared wall
Wrinkled appearance
Several yrs in soil
-Slow motility
-spiky projection

27. Acanthameoba sp: Pathology:
• Rarely causes damage in people with intact immune
systems
• Most common cause of corneal ulcers and keratitis in
contact lens wearers
Mainly causes
A- Amebic Keratitis
B- chronic Granulomates meningoencephalitis

28. B- Amebic Keratitis
•predisposing factors
•ocular trauma
•contact lens (contaminated
cleaning solutions)
•symptoms
•ocular pain
•corneal lesions (refractory to
usual treatments)
•diagnosis
•demonstration of amebas in
corneal scrapings
•Treatment- difficult, limited success
• A vision threatening chronic inflammation of the
cornea

30. Acanthamoeba: Pathology
• AIDS Patients and other immune
suppressed individuals cannot fight the
amoeba
– May cause skin ulcerations, keratitis, and
corneal ulcerations
– In rare cases, it can cause problems in the
central nervous system of immune suppressed
individuals.
• Can cause meningoencephalitis like N. fowleri

31. B- chronic Granulomates meningoencephalitis
• associated with immunosuppression
• onset is insidious with headache, personality changes,
slight fever
• Prolonged clinical course, weeks to months to
progresses to coma and death
• amebas not yet detected in spinal fluid
• In contrast to naegleria, both trophozoites and
sometimes cysts are detected in histological
examination
• no human cures documented
• Diagnosis is difficult usually done at autopsy

32. Brain damage due to
Acanthamoeba
Acanthamoeba killing
cornea epithelium cells

33. In culture
Aacanthamoeba trophozoites are distinguished by its spiky
pseudopodia

34. In histological examination, naeglaria &
acanthamoeba trophozoite are
indistingushable

35. A comparison of Naegleria-Acanthamoeba morphology with
Entamoeba histolytica
Naegleria-Acanthamoeba Entamoeba
1. Nucleoulus large and
distinct
2. Single nucleus in cyst.
3. Contractile vacuoles
present
4. No glycogen and
chrmatoid
1. Nucleolus small and indistinct.
2. Four nuclei in a mature cyst
3. Contractile vacuoles absent
4. Glycogen and chromatoid
bodies in cyst
5. Mitochondria absent

36. A comparison of Naegelria morphology with Acanthamoeba
Naegleria Acanthamoeba
1.Trophozoite displays
broad pseudopods
2. Activity motile
3. Form flagellate stage
4. Thin walled cysts
5. Cyst wall has no pores
6. Does not encyst in
tissues
1. Trophozoite displays filamen-tous
pseudopods (acanthopodia)
2. Sluggishly motile
3. Does not form flagellate stage
4. Double walled cysts
5. cyst wall may have pores or osteioles
6. May encyst in tissues

37. Acanthamoeba: Treatment
• Blindness has been treated by corneal transplants.
– Prevention by using store-bought saline solution or
distilled water to make saline solution
– If corneal abrasion continues, stop wearing contacts.
• Treatment of people with suppressed immune
system is difficult.
– Miconazale and ketaconazole seem to work the best.
– Some bacteria make chemicals that kill amoeba

38. Acanthamoeba: summary
• ubiquitous ameba of the soil and water
• human cases first reported in the early 1970's
• In contrast to PAM, it is associated with chronically
ill, immunocompromised and other debilitated patient
• Like naegleria, is neutrotropic and causes
encephelites
• GAE is slowly progressing and chronic type
• Also associated with lesion in the cornea

39. A comparison of Naegleria-Acanthamoeba morphology with
Entamoeba histolytica
Naegleria-Acanthamoeba Entamoeba
1. Nucleoulus large and
distinct
2. Single nucleus in cyst.
3. Contractile vacuoles
present
4. No glycogen and
chrmatoid
1. Nucleolus small and indistinct.
2. Four nuclei in a mature cyst
3. Contractile vacuoles absent
4. Glycogen and chromatoid
bodies in cyst
5. Mitochondria absent

40. A comparison of Naegelria morphology with Acanthamoeba
Naegleria Acanthamoeba
1.Trophozoite displays
broad pseudopods
2. Activity motile
3. Form flagellate stage
4. Thin walled cysts
5. Cyst wall has no pores
6. Does not encyst in
tissues
1. Trophozoite displays filamen-tous
pseudopods (acanthopodia)
2. Sluggishly motile
3. Does not form flagellate stage
4. Double walled cysts
5. cyst wall may have pores or osteioles
6. May encyst in tissues