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[Giardia intestinalis (syn. Giardia lamblia)]

Giardia intestinalis cysts are oval to ellipsoid and measure 8-19 µm (average 10-14 µm).  Mature cysts have 4 nuclei, while immature cysts have two.  Nuclei and fibrils are visible in both iodine-stained wet mounts and trichrome-stained smears.

A	B

A, B, C, D: G. intestinalis cysts stained with trichrome.  Sometimes the cytoplasm of the cyst may retract from the cell wall; this is visible in Images A-D.

C	D