TABLE 2.

Encysted protozoan parasites in human feces, differentiated by general size, shape, and features

Parasite	General size (μm)	Shape	Features
Sarcocystis hominis and S. suihominis			Excreted sporulated
Oocysts	15-19 by 15-20	Spherical	Contain 2 sporocysts
Sporocysts	15-19 by 8-10	Oval	Contain 4 sporozoites
Isospora belli	20-33 by 10-19	Ovoid with tapered ends	Excreted unsporulated
Cyclospora cayetanensis	7.7-10	Spherical	Excreted unsporulated
Giardia duodenalis	11-14	Ovoid to ellipsoid	4 nuclei
Balantidium coli	50-70	Spherical to oval	Large macronucleus, thick wall
Cryptosporidium hominis and C. parvum	4.5 by 5.0	Nearly spherical	Excreted sporulated, but sporozoites hard to see
Entamoeba histolytica and E. dispar	12-15	Spherical	Uni- and binucleate, usually with distinct karyosome