Comparative population genetic structure of the mitochondrial 16S ribosomal RNA gene of Haemaphysalis flava (Acari: Ixodidae) between Nantong, China, and regions along the East Asia-Australasian Flyway.

Haemaphysalis flava Neumann, 1897 is recognized as a vector for Dabie bandavirus (severe fever with thrombocytopenia syndrome virus, SFTSV), which is the etiological agent of severe fever with thrombocytopenia syndrome (SFTS). The tick vector has proliferated and expanded globally in recent years, likely due to the migration of birds. In this study, we selected the mitochondrial 16S rRNA as the genetic marker to analyze the population genetics of H. flava collected from Nantong, China and other regions separated by geographical barriers, all of which are located along the East Asia-Australasian Flyway (EAAF). Our research revealed significant gene flow among tick populations, which are characterized by low genetic diversity, minimal phylogeographic structure, and the interconnected haplotype network. We identified a total of 38 haplotypes, including 5 shared haplotypes. The high overall average of haplotype diversity, the shared haplotypes with large sample size covering many regions, and the abundant exclusive haplotypes in our study supported that H. flava had the ability to adapt to different environments among the large geographical range along the EAAF. The study did not support the recent expansion of the H. flava population in Nantong. Continuous surveillance of H. flava along the EAAF is essential.