A number of cells and other organisms can easily be confused with intestinal protozoa: for example, polymorphonuclear leucocytes, macrophages, yeast and bacteria.

Clinically significant intestinal protozoa include amoeba, ciliates, flagellates, coccidia and microsporidia.

• Entamoeba histolytica
• Entamoeba coli
• Endolimax nana
• Blastocystis hominis

Flagellates

• Giardia lamblia
• Dientamoeba fragilis

Coccidia and Microsporidia

• Cryptosporidium species
• Cyclospora sp. (Cyanobacterium-like or coccidian-like body)
• Microsporidia

Tissue Protozoans

• Pneumocystis carinii