Molecular and phylogenetic insights into haemosporidian parasites in wild bird populations of Northeast Thailand.

Haemosporidian parasites, including Plasmodium, Haemoproteus, and Leucocytozoon, are widespread avian pathogens that significantly affect bird health and population dynamics. Despite their ecological importance, molecular data on these parasites in avian populations from Northeast Thailand remain limited. This study investigated the prevalence, genetic diversity, and phylogenetic relationships of haemosporidian parasites infecting wild birds in Maha Sarakham Province, Thailand. A total of 107 wild bird samples, comprising 61 Zebra Doves (Geopelia striata) and 46 House Sparrows (Passer domesticus) were screened for haemosporidian infection using multiplex PCR targeting the cytochrome b (cyt b) gene. The overall prevalence of haemosporidian infection was 52.3 % (56/107), with Plasmodium spp. (33.6 %) being the most common, followed by Haemoproteus spp. (29.0 %). No infections with Leucocytozoon spp. were detected. Co-infections with Plasmodium and Haemoproteus were observed in 11 House Sparrows. DNA analysis identified Plasmodium sp., P. collidatum, and Haemoproteus sp. as the predominant parasites. Phylogenetic analysis of 45 successfully sequenced samples revealed nine distinct haplotypes, including four novel lineages, three Haemoproteus (GEOSTR01, GEOSTR03, PASDOM02) and one Plasmodium (PASDOM01). Haemoproteus lineages showed strong host specificity, with those from Zebra Doves forming a distinct clade separate from passerine-associated lineages. In contrast, Plasmodium lineages exhibited broader host associations, consistent with vector-mediated transmission across species. This study contributes to the understanding of haemosporidian diversity in Thai avifauna and underscores the importance of molecular surveillance in avian disease ecology. Notably, this is the first report of the highly virulent avian malaria parasite P. collidatum in wild bird populations in Thailand.