Names of diseases caused by protozoa include malaria, diarrhea, dysentery and colitis. In animals, the organisms may cause coccidiosis and toxoplasmosis. Symptoms of a protozoan infection include nausea, abdominal pain and bloating.
Protozoa that live in a human’s intestine may be passed to another human via fecal-oral means, such as ingestion of contaminated food or water. Protozoan in human blood and tissue may be transmitted by an arthropod vector.
Protozoa are single-celled organisms that are too tiny to be seen with the naked eye, and their ability to multiply very fast in humans enhances their ability to survive. Some protozoa include Cryptosporidium parvum, Isospora belli and Balantidium coli.