Taxonomy: f. Entamoebidae
Animal: Entamoeba histolytica 3 09.jpg
Sites: Gut
Entamoeba histolytica cysts - spherical 10 - 20 microns (average 12 - 15). Mature cyst has 4 nuclei - fine peripheral chromatin, small compact central karyosome and elongate chromatoidal bodies which have blunt or rounded smooth edges in faecal smear stained with PTAH. Clinical notes and travel history are essential in determining tests required. If the faeces is not examined within 1/2 hour of passing to see motile trophozoites OR fixed immediately with PVA fixative, protozoan parasites deteriorate and may be missed; this is particularly relevant for liquid or soft stools specimens from people who have travelled to areas of poor hygiene and children less than 10 years. It is essential for identification to examine stained (FeHX or Trichrome) smear as well as saline and iodine preparations. Preferably 3 specimens collected on alternate days over 10 days should be examined; if amoebiasis is suspected, 6 specimens over 14 days should be examined. To ensure cure, specimens should be examined 3-4 weeks after treatment. Serological tests, biopsies and various molecular tests may also be useful.

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