Endolimax nana

Diagnostic Form:

Cyst and trophozoite forms detected in stool specimens are diagnostic.

Formalin preserved stool concentrates treated with Lugol's Iodine are used to detect the cyst form of the amoeba. The cyst is spherical-oval-ellipsoidal in shape and can be 5-10 µm in diameter. Mature cysts will contain up to 4 nucleus while immature cysts are rarely. There is no peripheral chromatin to the nucleus and the karyosomal chromatin is large and usually centrally located. The cytoplasm of the cyst does not contain chromatoid body-bars but rather small granules or oval masses occasionally can be seen. A glycogen mass can be seen that is usually diffuse in young cysts that stain reddish brown with Lugol's Iodine.


Trichrome stained smears can be used to detect cysts and trophozoites in preserved stool specimens. The trophozoites can range between 6-12 µm in length. When a fresh stool is examined directly under the microscope, a motility is sluggish and or nearly nonprogressive. The trophozoites contain only one nucleus, that are visible occasionally in unstained preparations, with no peripheral chromatin present. The interior karyosomal chromatin is large, irregularly shaped and blot-like. The cytoplasm is granular; vacuolated; containing bacteria.

shell operculum knob interior


Geographic Prevalence:

The amoeba has a worldwide distribution.


Disease It Causes And The Clinical Symptoms:

Endolimax nana is not known to cause any disease in humans.


Location In The Host:

Small intestine.


Primary Vector:

None. The amoeba is acquired by the ingestion of cyst contaminated water or food.


Test Recommended For Detection/Diagnosis:

A full ova and parasite examination of the stool will detect the presence of Endolimax nana.