Deciphering the Evolutionary Dynamics: A Phylogenetic Analysis of Contemporary Tacheng Tick Virus Strains
Venu Paritala, Harsha Thummala, Sukesh Kalva, Rajashekhar Reddy ShagamreddyObjectives
This study aims to present the first molecular evidence of Tacheng tick virus-1 (TcTV-1) in Hyalomma aegyptium ticks collected from Turkey. It also seeks to characterise the genetic features of the Turkish TcTV-1 strain and identify its closest evolutionary relationship among known global TcTV-1 strains.
Material and Methods
Nucleotide sequences of the RNA-dependent RNA polymerase ( RdRp ) gene were retrieved from National Center for Biotechnology Information (NCBI). A total of 26 TcTV sequences were selected through Basic Local Alignment Search Tool (BLAST) analysis. Multiple sequence alignment and phylogenetic tree construction were performed using R packages (seqinr, msa, ape, ggtree) and validated in MEGA X using the maximum likelihood (ML) method. Substitution model fitting, Tajima’s neutrality test, and substitution pattern analysis were also conducted. Tamura-Nei and Kimura 2-parameter models were used to estimate evolutionary distances. Model selection was based on values. Tajima’s D statistic was calculated to evaluate neutrality and population dynamics.
Results
The Turkish TcTV-1 strain formed a distinct phylogenetic cluster, separate from the Chinese strains, suggesting regional divergence. The closest match to the Turkish isolate was TcTV-1 strain KT809539.1 from China, indicating a possible evolutionary linkage. Evolutionary rates showed site-specific heterogeneity based on gamma distribution parameters. A clear bias toward transitions over transversions was observed in substitution patterns. Tajima’s D value was negative, supporting population expansion and purifying selection.
Conclusion
This study confirms the presence of TcTV-1 in Hyalomma aegyptium ticks in Turkey for the first time. Phylogenetic analysis revealed that the Turkish strain is most closely related to the Chinese TcTV-1 strain KT809539.1, highlighting a likely evolutionary connection. These findings contribute to the growing understanding of TcTV-1’s geographic spread and evolution and establish a validated R-based workflow for future molecular surveillance.