Every species of bird has at least one species of endoparasite or ectoparasite, if not several. Thus it cannot be taken for granted that a particular individual avian species is free from haemosporidian infections. Birds have the richest diversity of intracellular, single cell, protozoan parasites with complicated life cycles, changing between the vector as definitive host (blood-feeding arthropod) and bird as intermediate host. Avian haemosporidian parasites belong to the order Haemospororida, to which the families Haemoprotidae, Plasmodiidae, Garniidae and Leucocytozoidae belong, consisting of the genera Haemoproteus, Plasmodium, Fallisia and Leucocytozoon.

Includes bibliographical references.