A. Characteristics of Protozoa Protozoa are unicellular eukaryotic microorganisms lacking a cell wall and belonging to the Kingdom Protista. Although there are nearly 20,000 species of protozoa, relatively few cause disease. Most inhabit soil and water.
Cysts allow some pathogens to survive outside their host.
We will now briefly look at some medically important protozoa classified into phyla based on their motility. Illustrations can be found in your Lab Manual in Lab 22. B. Medically Important Protozoa 1. Acanthamoeba can infect the eye, blood, spinal cord, and brain and is transmitted by waterborne cysts picked up while swimming in contaminated water, crossing the mucous membranes. It does not produce a cysts stage and is usually transmitted by sexual contact.