How big is a protozoa?

Protozoa range in size from 1/5,000 to 1/50 of an inch (5 to 500 micrometers) in diameter. They are microscopic. The term protozoa means first animal. They are found everywhere and they eat bacteria, algae and other protozoans. Examples that are interesting to us are the flagellate Trypanosoma, which causes African sleeping sickness; the amoeba Entamoeba histolytica, which can attack the intestinal wall and cause amoebic dysentery, and the sporozoans of the Plasmodium species, which cause malaria.