Haemoproteus is a genus of alveolates that are parasitic in birds, reptiles, and amphibians. Its name is derived from Greek: haima 'blood' and Proteus, a sea god that had the power to assume various shapes. The name Haemoproteus was first used in the description of H. columbae in the blood of the pigeon Columba livia by Walther Kruse in 1890. This was also the first description of this genus. Two other genera—Halteridium and Simondia—are now considered to be synonyms of Haemoproteus.

Plasmodium is a genus of unicellular eukaryotes that are obligate parasites of vertebrates and insects. The life cycles of Plasmodium species involve development in a blood-feeding insect host which then injects parasites into a vertebrate host during a blood meal. Parasites grow within a vertebrate body tissue before entering the bloodstream to infect red blood cells. The ensuing destruction of host red blood cells can result in malaria. During this infection, some parasites are picked up by a blood-feeding insect, continuing the life cycle.