. Author manuscript; available in PMC: 2016 Jun 1.

Published in final edited form as: Clin Lab Med. 2015 Apr 4;35(2):423–444. doi: 10.1016/j.cll.2015.02.010

Table 3.

Comparative morphology of Giardia duodenalis, Cryptosporidium spp, Cyclospora cayetanensis, and Cystoisospora belli

Organism	Size	Other Morphologic Features	Preferred Morphologic Diagnostic Test
Giardia duodenalis	Trophozoites, 10–20 μm long Cysts 8.0–10 μm long	Trophozoites: pyriform shape; sucking disk; 2 nuclei; 2 median bodies; 8 flagella (4 lateral, 2 ventral, 2 posterior) Cysts: ovoid shape; 2–4 nuclei; fibrils and median bodies; no flagella	Trophozoites: direct wet mount; trichrome stain Cysts: FEA concentration wet mount; trichrome stain
Cryptosporidium spp	Oocysts: 4.0–6.0 μm	Oocysts: spherical shape; sporulated in feces (4 sporozoites present)	Modified acid-fast stain; Safranin stain
Cyclospora cayetanensis	Oocysts: 8.0–10 μm	Oocysts: spherical; unsporulated in fresh feces; refractile globules present	Modified acid-fast stain; Safranin stain; UV microscopy
Cystoisospora belli	Oocysts: 20–33 μm long	Oocysts: oval to ellipsoidal shape; unsporulated in fresh feces; double-layered hyaline cyst wall; single sporoblast usually present	Modified acid-fast stain; safranin stain; UV microscopy