A phylum consisting largely of mouthless protozoans that are all parasitic and have no obvious means of locomotion: Most of the minute unicellular organisms of the Sporozoa pass through a complicated life cycle involving an alternation of sexual and asexual reproduction and the formation of spores.

Some, such as the malaria parasite, live in the blood of the host; others may infest the gut or the muscles. They are often transmitted by blood-sucking insects.

Go to this Sporozoa link for additional information.