Hematozoa is a subclass of blood parasites of Apicomplexa clade. Well known examples include Plasmodium spp. causing the human malaria, or Theileria in cattles, but a large number of species are known to infect birds and are transmitted by arthropod vectors. Hematozoa is a subclass of blood parasites of Apicomplexa clade. Well known examples include Plasmodium spp. causing the human malaria, or Theileria in cattles, but a large number of species are known to infect birds and are transmitted by arthropod vectors.