An Integrative Assessment of Tabanus rubidus (Diptera: Tabanidae) in Thailand: Distribution, Population Genetics, and...

Tabanus rubidus (Diptera: Tabanidae) is a significant species of the Tabanidae family, known for its veterinary and medical relevance, and is found across Thailand. This study examines the species distribution, genetic diversity, demographic history, and vector-pathogen transmission of T. rubidus collected from all six different regions in Thailand. Molecular techniques, utilizing the cox1 gene, were used to assess genetic diversity, genetic structure, and demographic history. The 16S ribosomal RNA gene was used to detect Anaplasma and Ehrlichia, while the 18S ribosomal RNA gene was used to identify Trypanosoma and Theileria. Tabanus rubidus was found in 23 out of 26 provinces in Thailand, indicating its widespread presence across the country. Negative binomial regression showed that fly abundance was negatively affected by monthly mean temperature but positively influenced by rainfall and site temperature. There was high haplotype diversity and low nucleotide diversity. The median-joining network network revealed three lineages: Lineage I, which includes Thailand, Malaysia, and Bangladesh; Lineage II, which is found in India and Bangladesh; and Lineage III, which is found in India. Analysis of the demographic history suggested that population expansion started at the end of the Pleistocene. In this study, T. rubidus tested negative for Ehrlichia and Theileria, with Trypanosoma theileri (T. theileri) and Anaplasma marginale being the only detected pathogens. These findings are epidemiologically significant, confirming tabanid-mediated transmission of T. theileri (indicator of trypanosomiasis) and A. marginale (agent of bovine anaplasmosis), both of which pose health risks and economic losses to livestock.