A genus of sporozoa (suborder Haemosporina) parasitic in birds and reptiles, combined with Leucocytozoon, Hepatocystis, and other genera in the family Haemoproteidae. Schizogony occurs in endothelial cells of blood vessels, especially in the lungs of the host, whereas halter-shaped gametocytes are found in the red blood cells. Infection is transmitted by pupiparous Diptera, such as louse flies (Hippoboscidae) and by bloodsucking midges (Culicoides) [G. haima, blood, + Proteus, a sea god who had the power of assuming different shapes]