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Endolimax nana Infection

Endolimax nana (Nonpathogen)

This organism belongs to the amebae, is a nonpathogen, and causes no disease.  Both the trophozoite (usual size, 8-10 µm) and cyst forms (usual size, 6-8 µm) can be found in clinical specimens.


Endolimax nana trophozoites    


Endolimax nana cysts

Life Cycle:
Intestine, organisms passed in feces

Fecal-oral transmission via cyst form; contaminated food and water

Worldwide, primarily human-to-human transmission

Clinical Features:

Clinical Specimen:
Intestinal:  Stool

Laboratory Diagnosis:
Intestinal:  Ova and Parasite examination (concentration, permanent stained smear); identification based on morphology

Organism Description:
Trophozoite:  No nuclear chromatin, large karyosome, relatively clean cytoplasm (may contain some debris); tremendous nuclear variation (can mimic Entamoeba hartmanni, Dientamoeba fragilis and Iodamoeba bütschlii).
Cyst:  May contain linear structures (pale), mature cyst contains 4 nuclei (rare to see two-nucleated stage).

Laboratory Report:
Endolimax nana (indicate cysts and/or trophozoites)


Improved hygiene, adequate disposal of fecal waste, adequate washing of contaminated fruits and vegetables

E. nana trophozoites can be difficult to differentiate from other organisms; note the tremendous nuclear variation in the trophozoite stage (see above).