Sequence-based analysis of Theileria annulata reveals high Tams1 gene diversity and conservation of 18 S rRNA in Türkiye.

Abstract

BACKGROUND: , a tick-borne apicomplexan parasite, causes tropical theileriosis in cattle, leading to significant economic losses in endemic regions. In our previous study,was detected in various bovine blood samples via sequencing, despite negative results from conventional species-specific PCR assays, suggesting potential sequence variation in diagnostic target regions. Building upon this observation, the present study aimed to investigate the genetic diversity and population structure ofisolates from T&#xfc;rkiye by analyzing two molecular markers with differing levels of variability: the conserved&#xa0;gene and the polymorphicgene. RESULTS: A total of 36 bovine blood DNA samples previously confirmed as-positive were analyzed using PCR and Sanger sequencing. All 36 sequences from thegene (717&#xa0;bp) were identical, forming a single haplotype, and indicating strong conservation of this locus. In contrast, thegene (584&#xa0;bp) yielded 27 distinct haplotypes among 34 sequences, demonstrating high haplotype diversity (Hd&#x2009;=&#x2009;0.988) and moderate nucleotide diversity (&#x3c0;&#x2009;=&#x2009;0.0307). Neutrality tests revealed a significantly positive Tajima&#x2019;s D (2.04089;&#x2009;<&#x2009;0.05) and a strongly negative Fu&#x2019;s Fs (&#x2013;5.685;&#x2009;=&#x2009;0.002) for theregion, indicating the presence of balancing selection and potential population expansion. Phylogenetic and haplotype network analyses further demonstrated significant genetic divergence within thegene region, suggesting the presence of multiple divergent lineages and localized genetic structuring among isolates. CONCLUSION: This study represents one of the few sequence-based efforts to characterize the genetic structure ofin T&#xfc;rkiye using both conserved and polymorphic molecular markers. The findings reveal substantial genetic diversity within thegene and underscore the limitations of relying solely on conserved targets for molecular diagnostics. These results suggest that regional variation in genetic diversity may influence diagnostic sensitivity, thereby supporting the potential value of incorporating polymorphic markers into surveillance strategies to improve epidemiological monitoring and control efforts.