1. The Amebae Old taxonomy: Phylum Sarcomastigophora Subphylum Sarcodina
New taxonomy: Phylum Sarcodina
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.

2. 2 Orders of Parasitic Amebae
ORDER AMOEBIDA - contains important parasites in the family Entamoebidae
- occur in the digestive tracts of vertebrates
- all are endoparasites
ORDER SCHIZOPYRENIDA - soil and water amebae that can become oppurtunistic parasites

3. General Life Cycle Ingested Cyst Trophs Binary Fission
Out into environment
Trophozoite (Troph) – Active feeding stage
Cyst – dormant, usually dispersal stage

4. Order Amoebida – 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.
First seen in 1878 but not described until 1903
Causative agent of the disease amebiasis (old name is Amebic Dysentery)

5. Geographic distribution
Parasite has worldwide distribution but is most common in the tropical regions of the world
 - it is estimated that up to 500 million people may be affected
- 100 million people suffer acute symptoms
 - may cause up to 100,000 deaths each year
 - a number of outbreaks have resulted from a breakdown in sanitation

6. Mode of transmission: Fecal/oral transmission (Ingestion of food and water contaminated by feces.)
Cysts survive longer in water than in food
Cysts can pass through intestines of cockroaches
Rarely transmitted through anal sex or anal then oral sex.
Location in host: Usually in the cecum but can be found in any part of the small and large intestines.
May be carried to liver, lungs, and other body parts if it perforates the intestines.

7. Entamoeba histolytica – 2 stages:
1. TROPHOZOITE - 20 to 30 µm in diameter
 - cytoplasm consists of clear ectoplasm, finely granular endoplasm; food vacuoles often containing RBCs are common
characteristic structure is the Spherical nucleus (4-7 mm) with small central nucleolus and characteristic radial spokes
living specimens show active, rapid movement
primary habitat of the trophozoites is the cecum.
but trophozoites have the ability to metastasize to other organs

8. Entamoeba histolytica trophozoites

9. 2. CYST - encystment is stimulated by harsh conditions
- trophozoite condenses into a sphere - the precyst
- precyst secretes cyst wall to form the round cyst - 10 to 20 m in diameter
- nuclear division begins after encystment:
Uninucleate cyst  Binucleate cyst  Quadrinucleate or mature cyst

10. Entamoeba histolytica cysts
Cyst nuclei possess even peripheral chromatin and a central karyosome (karyosome position may be off-center in some stained specimens)
cytoplasm contains rod-shaped Chromatoidal bodies cigar-shaped areas of packaged semicrystalline arrays of riobosomes - and vacuoles
chromatoidal bars and vacuoles are most common in young cysts (uninucleate & binucleate).

11. Entamoeba histolytica cysts
uninucleate cyst binucleate cyst

12. Entamoeba histolytica cysts
quadrinucleate or mature cysts – diagnostic in feces

13. Entamoeba histolytica life cycle
Cysts are susceptible to heat (above 40 C.), freezing (below –5 C.), and drying
Cysts remain viable in moist environment for 1 month
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-oral contamination

15. Entamoeba histolytica pathology
1. COLONIZATION OF THE
LARGE INTESTINE
Amoeba invade mucosa and
erode through laminia propria
causing characterisitic flask
shaped ulcers contained by
muscularis
proteolytic enzymes :
hyaluronidase
Ulcers may form sinuses and extend into the submucosa

16. Entamoeba histolytica pathology
1. COLONIZATION OF THE LARGE INTESTINE
primary ulcer
Mucosa
submucosa

17. Entamoeba histolytica pathology
2. COMPLICATIONS IN LARGE INTESTINE
 A. Ulcers extend deep into the submucusa and may extend completely through the large intestine causing a secondary infection (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

19. Entamoeba histolytica pathology
EXTRA-INTESTINAL LESIONS (Amebiasis)
the parasite can enter the blood stream and be swept to other organs:
1.Liver most commonly invaded
Digests liver cells
Causes abscesses
2.Lungs are usually invade next.
3.May also invade heart, brain, kidneys, skin and any other organ.

20. movement of trophozoites from large intestine to lungs via hepatic portal vein
Liver abscesses

21. Symptoms Depends on host’s previous exposure to parasite
Chronic, low-level exposure can result in host being asymptomatic.
Less frequent exposure result in severe symptoms.
May also depend on nutritional status of host
Amoebic dysentery
Ranges from minor cramping and diarrhea to severe cramping and 15 to 20 bloody stools a day

22. Symptoms
Colitis is the most common form of disease associated with amoebae
Gradual onset of abdominal pain, watery stools containing mucus and blood
Some patients have only intermittent diarrhea alternating with constipation
Fever is uncommon
Formation of ulcers

23. Amebic colitis Sign or Symptom % of Patients Affected
Symptoms > 1 wk Most patients
Diarrhea
Dysentery
Abdominal pain
Weight loss
Fever >38oC 10
Heme (+) stool
Immigrant from or traveler
to endemic area >50
Prevalence (male/female) /50

24. Acute Fulminant or Necrotizing Colitis
Unusual (about 0.5% of cases)
A complication that occurs more frequently in patients inappropriately treated with corticosteroid

25. Ameboma
Segmented mass of granulation tissue in the cecum or ascending colon
Occurs in 0.5% to 1.5% of patients with intestinal amebiasis
Lesions resolve with anti-amebic chemotherapy

26. Amebic liver abscess Most common form of extraintestinal amebiasis
Fast growing abscess filled with debris, amoebae are found only at borders

27. Develops in about 10% of patients with invasive
Amebic Liver Abscess
Develops in about 10% of patients with invasive
E. histolytica infections
Few patients have concurrent dysentery – most report dysentery within the preceding year
Occurs in any age group
Patients with a more chronic illness (2-12 weeks of symptoms) commonly present with hepatomegaly and weight loss

28. Amebic Liver Abscess Sign or Symptom % of Patients Affected
Symptoms > 4 wks
Fever
Abdominal tenderness
Hepatomegaly
Jaundice
Diarrhea
Weight loss
Cough
Immigrant from or traveler
to endemic area >50
Prevalence (male/female) /50 in children; 90/10 in adults

29. Diagnosis 1.Stool examination
trophozoite
cyst
specimen
feces
method
direct smear with normal saline
direct smear with iodine stain
diseases
amoebic dysentery
chronic intestinal amoebiasis or carriers
remarks
1.container must clean 2.examined soon after they have been passed. 3.select bloody and mucous portion.
4.keep specimen warm.
5.drug using history.　

30. Diagnosis
2. Serologic studies: indirect hemagglutination, skin tests, ELISA and latex agglutination.
3. Tissue examination: sigmoidoscopic biopsy, aspiration
4. PCR

31. TREATMENT Asymptomatic: Iodoquinol 650 mg 20 d – Paromomycin
Mild to moderate : Metronidazole mg d
(Intestinal disease) Tinidazole 2g once daily 3d
Severe intestinal and : Metronidazole 750 mg d
Extraintestinal disease Tinidazole 2g once daily 5d

32. Commensal hypothesis
E. histolytica usually is a benign gut commensal as many other amoebae (minuta form)
A certain stimulus (gut flora, diet, host immune status …) transforms the organism into a pathogen (magna form, Kuenen, 1913)
This has been the accepted view for most of the 20th century

33. 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 m in diameter  
 - nuclear structure is similar (endosome in center) but
peripheral chromatin is more irregular
  - cysts are m in diameter and contain 4 nuclei

34. Entamoeba dispar
There are two morphologically indistinguishable species: E. histolytica and E. dispar. Only one of them (hystolytica) causes disease while the other is benign (Brumpt, 1928)
This theory was entirely discounted and ridiculed
Recent molecular data have revived this two species hypothesis
We now know that most people are infected with the nonpathogenic Entamoeba dispar

35. Non-pathogenic Amebae
Entamoeba coli
Definitive Host: Humans
Intermediate Host: None
Geographic distribution: Cosmopolitan
Much more common than E. histolytica
More hardy, resistant to putrefaction.
Mode of transmission: Ingestion of contaminated food and water.

36. Entamoeba coli life cycle stages
1. TROPHOZOITE - 20 to 30 m in diameter 
- granular endoplasm is coarser than E. histolytica
  - structure of nucleus: eccentric karyosome – marginal chromatin is ordinarily
coarser, with larger granules
- lives in large intestine and feeds on bacteria and any other cells available to it; does not invade tissue

37. 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?

38. Entamoeba coli life cycle

39. Entamoeba gingivalis
Definitive Host: Humans. Also other primates, dogs, and cats.
Geographic distribution: Cosmopolitan
In some areas about 50% of the population have it.
Up to 95% of “unhealthy” mouths have it.
Mode of transmission: Direct oral contact (kissing).

40. Pathology and Treatment: None
Location in Definitive host: 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.
Pathology and Treatment: None
More common in mouths with gingivitis and tonsillitis
Most likely due to abundance of food in “dirty” mouth.
Diagnosis: Sample of scrapings from teeth

41. E. gingivalis Life Cycle
Trophs in mouth
Binary Fission
Direct oral contact passes it to next host.
No cyst stage. Never goes out to external environment.

42. Endolimax nana Definitive Host: Humans Intermediate Host: None
Geographic distribution: Cosmopolitan
Mode of transmission: Ingestion of contaminated food and water.

43. 2 stages in the life cycle:
1. TROPHOZOITE - small in size; µm (usually under 10 m)
- structure of nucleus: small with large
endosome –marginal chromatin is thin
  moves slowly; feeds on bacteria and food debris 

44. Endolimax nana 2. CYST - forms as feces dehydrates
- small in size ( m)
- contains 4 nuclei with large endosomes

45. E. nana Life Cycle Ingested Cyst Trophs in large intestines
Binary Fission
Ingested
Cyst
Out into environment
Change in chemistry as troph moves down colon tells the troph to form a cyst.

46. Iodamoeba butschlii Geographic distribution: Cosmopolitan
Mode of transmission: Ingestion of contaminated food and water.
Location in Definitive host: Cecum and large intestine.
Pathology and Treatment: Harmless commensal
Feeds on bacteria, yeast, and wastes in intestines
Diagnosis: Important to distinguish between it and E. histolytica
Avoid unnecessary treatment
Large, clear vacoule in trophs and cysts .Different shape nuclei.

47. 1. TROPHOZOITE - 9 to 20 m in diameter
  structure of nucleus: large and vesicular.
large endosome. no peripheral chromatin
  feed on bacteria and yeast; do not invade
tissue

48. 2. CYST - 6 to 15 m in diameter
- large nucleus with large endosome and lightly-stained granules
- large glycogen vacuole (appears clear) in cytoplasm
- stains deeply with iodine; hence, the genus name

49. Iodamoeba bütschlii life cycle

50. Order Schizopyrenida – Facultative Amebae
Members of the Order Schizopyrenida are normal inhabitants of soil and water where they feed on bacteria.
A few members have the ability to become facultative parasites when an opportunity to enter a vertebrate exists.
Three are able to infect humans:
Naegleria fowleri
primary amebic meningoencephalitis (PAM)
2. Acanthamoeba spp.
granulomatous amebic encephalitis (GAE)
3. Balamuthia mandrillaris
GAE + granulomatous skin and lung lesions

51. Naegleria fowleri Geographic Range: Cosmopolitan
Found throughout world in freshwater.
Three life forms: amoeba, flagellate, cyst
Suckerlike structures called amebastomes
Infections generally occur around thermal pools where population of amoeba is high.
Also very common in water above 80oF
~ 200 documented cases worldwide
81 in U.S.
14 cases from same lake in Virginia
16 cases from same stream feed pool in Czech Republic

53. Naegleria fowleri ~ 200 documented cases worldwide 81 in U.S.
14 cases from same lake in Virginia
16 cases from same stream feed pool in Czech Republic
The case fatality rate is estimated at 98%

54. Naegleria Life Cycle low nutrients desiccation Trophozoite =
feeding and replicating form
desiccation
Cyst = dormant form

55. If flagellate form is inhaled, it quickly changes to the amoeba form
Mode of transmission: Inhalation of water containing amoeba or flagellate form.
If flagellate form is inhaled, it quickly changes to the amoeba form
Cysts are not infective at all and are not formed in the host.
Usually accidental but is sometimes intentional
Sniffing water to clear nasal passages
Location in the definitive host: Brain
- all victims have had a history of swimming in freshwater lakes or ponds or swimming pools a few days before the onset of symptoms

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

58. Primary Amebic Meningoencephalitis (PAM)
1-14 days incubation period
symptoms usually within a few days after swimming in warm still waters
infection believed to be introduced through nasal cavity and olfactory bulbs
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
4 known survivors treated with Amphotericin B

59. brain section

60. May be possible to diagnose with spinal tap.
DIAGNOSIS – most cases have been diagnosed at autopsy by identification of large numbers of amebae in the brain tissues
May be possible to diagnose with spinal tap.
Look for trophozoites each with a nucleus with large karyosome
real time PCR
Disease is so rare and the brain tissue destruction is so rapid that diagnosis is seldom made in time
TREATMENT
Amphotericin B 1.5 mg/kg/d in 2 doses × 3d ,then
1 mg/kg/d × 6d

61. N. fowleri found in water everywhere but very rarely causes infection.
N. fowleri: Final notes
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.

62. 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: They have small spiky acanthopodia and move very slowly.

63. Geographic Distribution: Cosmopolitan
Found in freshwater almost everywhere
Amoeba and cyst forms
Cannot survive in thermal pools
Mode of transmission: invades body through cuts and abrasions.
Location in Host: Most common in eye and skin. Rarely invades brain.
majority of patients are chronically ill, immunocompromised, or debilitated with other diseases
also produces amebic keratitis and skin and lung lesions

64. Acanthamoeba life cycle

65. Acanthamoeba spp. pathology
These species cause 2 pathological effects:
1- AIDS Patients and other immune suppressed individuals cannot fight the amoeba
May cause skin ulcerations, keratitis, and corneal ulcerations
Over 100 cases of granulomatous amebic meningoencephalitis caused by Acanthamoeba have been documented
Most, however, resulted in death in a few months.
Mode of transmission is not known, as no history of swimming occurred in some cases.

66. Acanthamoeba spp. pathology
2. Most common cause of corneal ulcers and keratitis in contact lens wearers
Keratitis is an inflammation of the cornea Can lead to blindness.
Most common in people who make their own saline solution.
also produces amebic skin and lung lesions

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

69. Diagnosis and Treatment
Diagnosis by identifying amebae in corneal scrapings
Drug treatment has been successful in most cases : Pentamidine, amphotricin B, ketoconazole, flucytosine.

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

71. morphology similar to Acanthamoeba
many Acanthamoeba GAE cases retrospectively assigned to Balamuthia
as of cases of Balamuthia (30 in U.S.)
thus far only identified post-mortem
environmental source not yet identified

72. CILIATES
The Phylum Ciliophora contains a single species of medical importance.  
Balantidium coli
Hosts and habitat: primarily a parasite of pigs. Strains adapted to various other hosts.
Lives in the cecum and colon.
Cosmopolitan in distribution but more common in the tropics ( Philippines).

73. Balantidium coli – Morphology of 2 stages
1. TROPHOZOITE - large ovoid ciliate; 30 to 150 µm in length (largest protozoan parasite of humans)
ID characters: cytostome, macronucleus, micronucleus, cillia
Reproduction: The trophozoite multiplies by transverse fission.
Trophozoites may possibly be infective if eaten.

74. Balantidium coli – Morphology of 2 stages
2. CYST - formed as feces dehydrate in the rectum
round shape; 40 – 60 µm in diameter; cyst wall is transparent
transmission: ingestion of cyst , usually in contaminated food or water.
 cyst is the diagnostic stage in a fecal smear

75. Life cycle

76. Pathology
Trophozoites are tissue invaders. They secrete proteolytic enzymes which digest the epithelium of the large intestine.
Hyaluronidaze could help enlarge the ulcer.
Flask shaped ulcers are formed in the mucosa of the large intestine and extend into the submucosa.
Ulceration results in bleeding and secondary bacterial infection.
Perforation of the large intestine has occurred in some fatal cases.

77. Secondary infections in other organs such as liver, lungs and urogenital organs are rare
Because B.coli is destroyed by a PH lover than 5, infection is most likely to occur in malnourished persons with low stomach acidity.

78. Diagnosis: Cysts are most commonly found in stools.
Large, sausage-shaped macronucleus. Micronucleus is often hidden from view by the macronucleus.
Treatment: Tetracycline 500 mg qid × 10d
Metronidazole 750 mg tid × 5d
Iodoquinol mg tid × 20d