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Amebiasis (Amebic Dysentery) Mustafa HA. Rasool MLT Dep. Hawler Health Technical College Email: [email protected] 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 Treatment of patients. Examination and treatment of food handlers. Environmental sanitation. Personal prophylaxis. Human feces should not be used as fertilizers. ………………………………………………………………………….. 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. ************************ Email: [email protected] Thank you