Genetic diversity, population structure and haplotype analysis of Babesia gibsoni based on the thrombospondin-related adhesive protein (TRAP) gene

This study investigated the genetic diversity, population structure, and evolutionary history of Babesia gibsoni thrombospondin-related adhesive protein (BgTRAP) gene. Phylogenetic analysis revealed three distinct genotypes (BgG1-BgG3) among 47 sequences. The newly generated Indian sequences (n = 12) grouped into BgG1 and BgG3, with BgG3 showing a broad geographical distribution across Japan, India, and Taiwan. The sequences exhibited 83.3–100% nucleotide and 76.3–100% amino acid similarities. A median-joining haplotype network analysis identified 27 haplotypes, with most being unique to one country. India had the highest haplotype diversity (h = 17), followed by Japan (h = 9) and Tunisia (h = 2). The haplotype diversity of the Indian population and the combined dataset exceeded 0.8, suggesting a very high level of genetic diversity. The overall dataset showed low nucleotide diversity (0.05519 ± 0.00292) but high haplotype diversity (0.926 ± 0.029). Significant genetic differentiation was observed between India and other countries, whereas negligible differentiation was found between Taiwan and Japan. Neutrality tests suggested a constant population size. This study provides the first comprehensive insight of B. gibsoni population genetics based on the BgTRAP gene, highlighting its potential as a marker for genetic diversity studies. The high genetic diversity and distinct genotypes suggest a complex evolutionary history of the parasite.