Molecular Characterization of Culicoides Species and Their Vector Potentials for Haemosporidia Infections in the İzmir Region of Türkiye.

Objective: This study aimed to determine the Culicoides species distributed across different districts of İzmir province, reveal their molecular characterization, and assess their vector potential for the transmission of avian haemosporidian parasites.

Methods: The study material comprised 800 female Culicoides specimens collected from Bergama, Ödemiş, Kemalpaşa, and Foça districts between May and August 2016. Following morphological identification, specimens from each identified species underwent molecular analyses. The mt-COI gene region of genomic DNA isolates from the specimens was amplified by polymerase chain reaction (PCR) and subjected to sequence analyses to reveal their molecular characterization and phylogenetic relationships. Haemosporidian DNA was investigated by nested PCR in the gDNA isolates of head/thorax (HTP) and abdomen pools, constituted from specimens separated by species and location. Molecular characterization of identified parasites was performed using sequence analyses.

Results: Morphological identification revealed that C. circumscriptus (39.4%) and C. imicola (33.8%) were the most common species in the research areas, followed by Culicoides sp. (ERU-Izm-Culi1) (9.1%), C. nubeculosus complex (7.6%), C. obsoletus (4.3%), C. gejgelensis (2.3%), C. punctatus (1.9%), and C. newsteadi (1.8%). A total of 175 polymorphic sites were distributed among the COI sequences of the obtained isolates, leading to the detection of 18 different haplotypes. The highest haplotype diversity was observed in C. circumscriptus, C. punctatus, and C. newsteadi. Phylogenetic analyses clustered the characterized haplotypes of Culicoides species into three major groups. Haemoproteus sp. GAGLA05 and H. minutus TURDUS2 lineages were detected in C. circumscriptus HTP genomic DNA isolates, providing evidence of this species' vector potential for Haemoproteus lineages in the research area.

Conclusion: This study determined the Culicoides species distributed in the İzmir Region using an integrated morphological and molecular diagnostic approach, providing original data for the molecular epidemiology of these important flies. Furthermore, the results suggest the potential importance of C. circumscriptus in the transmission dynamics of Haemoproteus lineages.