Download Entamoeba histolytica

Amebiasis
(Amebic Dysentery)
Mustafa HA. Rasool
MLT Dep.
Hawler Health Technical College
The Ameba
Ameba are characterized by possessing clear protoplasm which form pseudopods ,
by which these organisms move and engulf bacteria and red blood cells for feeding
purposes.
The most common ameba's seen in the intestinal tract of human are:
1- Entamoeba histolytica.
Pathogenic
2- Entamoeba dispar.
Nonpathogenic
3- Entamoeba coli.
Nonpathogenic
4- Entamoeba hartmani.
Nonpathogenic
5- Entamoeba gingivales.
Nonpathogenic
6- Endolimax nana.
Nonpathogenic
7- Iodamoeba buschlii.
Nonpathogenic
Entamoeba histolytica
Medical important protozoa .
Class: Sarcodina (Rhizopoda).
Genus: Entamoeba
Species: histolytica
caecum
Disease: Amebiasis
Habitat: caecum and sigmoidorectal region of man.
Stages: cyst and trophozoit
Infective stage:
Quadrinucleate cyst.
Morphology of Trophozoite(vegetative form):
Size: 10-60 X 15-30 mic. average (20-25 mic)
Cytoplasm is clearly differentiated into:
Ectoplasm: is clear with well developed pseudopodia.
Endoplasm: dense & fine granular enclosing:
Nucleus: spherical containing central karyosome & peripheral evenly distributed
small chromatin dots.
Food vacuoles: contain leucocytes,bacteria and rbc.
Motility: is raped and unidirectional by pseudopods.
Morphology of Cyst (cyst form):
Precyst stage:10-60 X 15-30 mic. average (15-20 mic)
-Round or oval with a blunt pseudopodia.
-Absent cyst wall
-Single nucleus present.
Cyst stage:10-20 mic. average (15 mic)
-Four nuclei are present in mature
quadrinucleated cyst
-Glycogen mass & chromatoid
bodies are present in immature
cysts –disappear in mature ones.
Cyst composition and
development
Life cycle of E. histolytica (Noninvasive form)
Intestinal infection occur through the ingestion of a mature quadrinucleate infective
cyst which contaminated food, drinks and also by hand to mouth contact. Then pass
through the stomach , as the cyst wall is resistant to gastric juice.
- In the intestine excystation takes place.
- Trophozoit being actively motile invade the tissue of the submucous layer of
large bowel.
- The trophozoit grow and multiply by binary fission.
- Invasion into blood vessels lead to intestinal lesions.
- After a time transformed to pre-cyst.
- A pre-cyst secret a cyst wall and become uninucleated cyst.
- Eventually mature quadrinucleated formed( infective form).
Life cycle of E. histolytica (Invasive form)
Pathogenesis
Trophozoite increase in number which produce local lesions (flask-shaped ulcer ) in
large intestine by producing histolytic enzymes that make necrosis of the intestinal
mucosa, invasion in the deeper mucosa lead to the secondary involvement of
another organs ( brain, liver, lungs and heart ) through blood stream, which cause
abscess and inflammation.
Symptoms
Asymptomatic: parasite in lumen and cysts pass in stool.
(healthy cyst passer – most common – more than 75%)
Symptomatic: (gradual onset), fever (low grade), diarrhea, dysentery, abdominal
pain, localized abdominal tenderness, & strain, painful spasm of anus (indicates
rectal ulceration).
Rare progressive disease of high mortality (high fever- severe bloody diarrhea –
diffuse tenderness – peritonitis)
Amoebic hepatitis or amoebic abscess, lung abscess, brain abscess or skin abscess
named extra-intestinal amebiasis.
Treatment
- Metronidazole, Tinidazole.
Very effective in killing amoebas in the wall of the intestine, in blood and in liver
abscesses.
- Diluxanide furoate.
kills trophozoites and cysts in the lumen of the intestine.
Epidemiology
Cyst passers are the main source of infection.
Cysts remain viable in faces for few days, in water for longer periods.
Cysts are killed by dryness, heat (over 55ºC) and by chlorine.
Control
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Treatment of patients.
Examination and treatment of food handlers.
Environmental sanitation.
Personal prophylaxis.
Human feces should not be used as fertilizers.
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OTHER AMEBAE INHABITING THE ALIMENTARY
CANAL
Most of these amoebae are commensal organisms that can parasitize the human
gastrointestinal tract.
Entamoeba dispar
E. dispar - formerly designated as non-pathogenic E. histolytica (non-invasive type).
9x more prevalent than E. histolytica
Morphologically identical with E. histolytica
their DNA and ribosomal RNA are different
- Trophozoite will have no ingested RBC
Entamoeba hartmanni
Morphologically indistinguishable from E. histolytica/E. dispar
Trophozoite
1- Similar to E. histolytica except
that it is much smaller (5-12 µm).
2- Ingest bacteria but does
not ingest RBCs.
Cyst
5-10µm, spherical in shape.
Mature: 4 nucleus with a
coarse cytoplasm.
immature cysts - Usually have
chromatoidal bars.
Entamoeba coli
most common endocommensal of humans, Feeds on bacteria and any other cells
available to it, does not invade tissues.
Trophozoites
1-More vacuolated or granular endoplasm with bacteria and debris but no RBCs.
2-Narrower, less differentiated ectoplasm.
3-Thicker nucleus with a large eccentric karyosome.
Cyst
1- Size: 10-35 μm ,usually spherical nucleus with eccentric karyosome.
2- Mature cyst: 8 nuclei, immature cyst: 2 or more nuclei.
3- Cytoplasm: coarsely granular with chromatoidal bodies.
Entamoeba gingivalis
- A common inhabitant of the mouth of man, lives on the surface of teeth and
gums, in gum pockets and sometimes in the tonsillar crypts.
- Organisms are more common in persons with pyorrhea
(gum disease)
they may cause of the condition.
Transmission: kissing, droplet spray and sharing eating utensils.
Has only trophozoite,10-20µm.
Moves quickly,
Has numerous food vacuoles that
contain cellular debris and bacteria
and ingested leukocytes.
Endolimax nana
Lives in the large intestine mainly near the cecum feed on bacteria.
Trophozoites
Small size of 6 to 15 µm, cytoplasm is granular, vacuolated and Pseudopodia are
hyaline.
Cyst
Spherical or ovoid in shape.
Chromatoidal bodies are not usually found.
Iodamoeba bϋtschlii
Lives in the large intestine, predominantly in the cecal areas
Has a very high prevalence in pigs and less in man.
Dientamoeba fragilis
It does not form cysts and trophozoites cannot survive passage through the small
intestine.
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