Definition
*Leucocytozoon* is a genus of parasitic protozoans that infect birds. These parasites infect both white blood cells (leukocytes) and red blood cells. They are transmitted by black flies or biting midges. *Leucocytozoon* infections can cause disease, particularly in young birds, leading to anemia and other health issues. Consider them avian blood parasites similar to malaria parasites. They impact bird health significantly. Their presence is a concern for ornithologists.