Genetic characterization of Rhipicephalus microplus (Acari: Ixodidae) in Africa reveals the presence of diverse haplotypes within a single clade: Implications for pathogens transmission and tick control in a predominantly pastoral production system

The Asian blue tick, Rhipicephalus (Boophilus) microplus (Canestrini, 1888) is renowned as a notorious pest of veterinary importance globally. Its recent introduction to West Africa and subsequent eastward invasion and displacement of native tick fauna in many African countries is alarming, considering the prevalent unrestricted livestock migration in these regions. This study determined the genetic diversity of R. microplus in Africa based on the mitochondrial cytochrome oxidase subunit one (cox1) gene sequences in comparison with global sequences. Phylogenetic and genetic diversity analyses showed that all the five Nigerian sequences in this study alongside other African R. microplus sequences clustered in Clade A and exhibited low haplotype (Hd = 0.371) and nucleotide (π = 0.00221) diversities compared to the global values of Hd = 0.782 and π = 0.04757, respectively. Four haplotypes, H1, H2, H4 (unique to Africa) and H5 were present in Africa. Though positive but not statistically significant, the Tajima's D (D = 0.126) and Fu's Fs test (Fs = 1.118) reflect a weak excess of intermediate-frequency variants that support the neutrality of the mitochondrial cox1 region across the sampled populations. However, pairwise comparisons revealed substantial genetic differentiation among continental populations ranging from moderate, between Africa and South America (0.402) to high, between South America and Asia (0.648), indicating limited maternal gene flow and pronounced population structure. Analysis of Molecular Variance results corroborated the strong genetic structuring with the variation among populations accounting for 71.1 % of the total genetic variance (p < 0.001). The rapid spread of R. microplus in Africa calls for urgent regional/continental actions to control its further spread and the attendant consequences. Our findings underscore the urgent need for targeted surveillance and control programs to mitigate the risk of acaricide resistance and pathogen transmission associated with this invasive tick.