Protozoan Infections

» The Protozoa » Amebiasis » Giardiasis

» African Trypanosomiasis » Cryptosporidiosis

The Protozoa
Protozoans are not animals. Animals by definition belong to the kingdom Animalia. Protozoans belong to the kingdom Protista. Protists are usually microscopic, single-celled organisms whereas animals and plants are multicellular. There are fungus-like protists, plant-like protists, and animal-like protists. The animal-like protists are called protozoans and although they are not animals, zoologists (scientists who study animals) have traditionally dealt with the protozoa.

Most protozoans are free-living and harmless to humans; however, some of the most serious diseases of humans, such as malaria, are caused by parasitic protozoa. Bacteria are also single celled organisms that are responsible for a plethora of human diseases such as anthrax, tuberculosis, cholera, plague, gonorrhea. Bacteria differ from protists in that they are prokaryotic cells, meaning they lack a true nucleus.

Protozoa are divided into groups based primarily on the nature of their locomotory structures, or those structures that they use to get around. The main groups include the amoebae who use pseudopodia, or false feet, to move, ciliates that use cilia to move, flagellates that have flagella, and apicomplexans which have no locomotory structures.