ABSTRACT
Although it is now widely accepted that the various species that traditionally are collectively categorized as “protozoa” are not necessarily closely related to each other, it remains a useful term in many situations relating to human and animal health. However, it should be noted that in many scientifi c contexts, this classifi cation is no longer formally used. Thus, the term ‘protozoan parasites’ as used within this chapter refers to those eukaryotic, unicellular, organisms that infect another organism, the host, obtaining benefi ts at the latter’s expense. For some infections with protozoan parasites, the host organism is severely weakened or compromised and, in some infections, may be killed.
