(prō-tă-zō′ă)
[Pronunciation]
[″ + zoon, animal]

The phylum of the kingdom Protista that includes unicellular, animal-like microorganisms.
Many protozoa are saprophytes that live on dead matter in water and soil. Many parasitic protozoa infect only humans without adequate immunological defenses, although a few infect immunocompetent persons. Infections are spread by the fecal-oral route, through ingestion of food or water contaminated with cysts or spores, or by the bite of a mosquito or other insect that has previously bitten an infected person. Common protozoan infections include malaria (Plasmodium vivax, P. malariae); gastroenteritis (Entamoeba histolytica, Giardia lamblia); leishmaniasis, an inflammatory skin or visceral disease (Leishmania species); sleeping sickness (Trypanosoma gambiense); and vaginal infections (Trichomonas vaginalis). Pneumocystis jiroveci, previously classified as a protozoon, is now categorized as a fungus. Opportunistic protozoan infections caused by Cryptosporidium parvum and Toxoplasma gondii are seen in patients who are immunosuppressed by disease or drug therapy.

Figure: PROTOZOA





Table of Pathogenic Protozoa