Definition
A leucocytozoan is a parasitic protozoan that infects the white blood cells (leukocytes) and red blood cells of birds. These parasites belong to the genus *Leucocytozoon*. They are transmitted by black flies or biting midges. Leucocytozoan infections can cause disease, particularly in young birds. Think of them as parasites targeting the immune system of birds. It is like a microscopic invader wreaking havoc inside bird’s blood. Their presence impacts avian health.