Haematozoa

Hematozoa is a subclass of blood parasites of the Apicomplexa clade. Well known examples include the Plasmodium spp. which cause malaria in humans and Theileria which causes theileriosis in cattle. A large number of species are known to infect birds and are transmitted by insect vectors. The pattern in which Haematozoa infect a host cell depends on the genera of the blood parasite. Plasmodium and Leucozytozoon displace the nucleus of the host cell so that the parasite can take control of the cell where as Hemoproteus completely envelops the nucleus in a host cell.

Infections of haematozoa can have adverse fitness effects on certain species. Species that have been isolated or have not been exposed to the infection have been found to be especially vulnerable to pathogenic effects. The infection effects can persist in avian host species through long-distance migrations.