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[Toxoplasma gondii]

Oocysts of Toxoplasma gondii are shed only in the feces of domestic and wild felids, the definitive hosts.  Sexual reproduction takes place in the intestinal epithelium of the cat host and cysts are shed unsporulated in the feces.  In the environment, cysts take 48-72 hours to sporulate and become infective.  Mature oocysts measure 10-12 µm in diameter and contain two sporocysts.  Human infection may occur either from ingestion of sporulated oocysts, or ingestion of meat infected with trophozoites.

A	B

A:  Unsporulated T. gondii oocyst in an unstained wet mount.
B:  Unsporulated oocyst of T. gondii in an unstained wet mount, viewed with differential interference contrast (DIC) microscopy.

C	D

C:  T. gondii oocysts in a fecal floatation.
D:  Higher magnification of Figure C.