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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: G. intestinalis cyst in a wet mount under differential interference contrast (DIC) microscopy.  Image taken at 1000× magnification.
B: Two G. intestinalis cysts in a wet mount under DIC microscopy; image taken at 1000× magnification.