The Leucocytozoon genus comprises numerous widely distributed parasites which have been less investigated than other avian hemoprotozoa. Their occurrence is common, with very variable prevalence values and pathogenicity degrees. Leucocytozoon species are characterized by a great taxonomic diversity, and infections are usually restricted to birds of the same family. In the present paper, a mixed hemosporidia infection by Leucocytozoon californicus and Haemoproteus sp. in an adult male merlin (Falco columbarius) which died during hospitalisation is reported, indicating, for the first time, a newly described avian host species. A molecular investigation was carried out through cytochrome b gene analysis, revealing a 100% match with L. californicus and Haemoproteus spp. A blood smear examination allowed us to detect Leucocytozoon fusiform mature gametocytes and different degrees of maturity of Haemoproteus gametocytes. Histopathology revealed foci of necrosis, hemorrhagic areas and extramedullary hematopoiesis in the liver, the presence of microthrombi in the heart and lung and scattered hemorrhages in the lung.
Keywords: Falco columbarius; Haemoproteus sp.; Leucocytozoon californicus; PCR; anatomopathological findings.