Protozoan infections are parasitic diseases caused by organisms formerly classified in the Kingdom Protozoa.They include organisms classified in Amoebozoa, Excavata, and Chromalveolata. Examples include Entamoeba histolytica, Plasmodium (some of which cause malaria), and Giardia lamblia.Trypanosoma brucei, transmitted by the tsetse fly and the cause of African sleeping sickness, is another example.hey include organisms classified in Amoebozoa, Excavata, and Chromalveolata. Examples include Entamoeba histolytica, Plasmodium (some of which cause malaria), and Giardia lamblia. Trypanosoma brucei, transmitted by the tsetse fly and the cause of African sleeping sickness, is another example.