Analyses of mitochondrial genes reveal two sympatric but genetically divergent lineages of Rhipicephalus appendiculatus in Kenya. Issue 1 (December 2016)

• Record Type: Journal Article
• Authors: Kanduma, Esther; Mwacharo, Joram; Githaka, Naftaly; Kinyanjui, Peter; Njuguna, Joyce; Kamau, Lucy; Kariuki, Edward; Mwaura, Stephen; Skilton, Robert; Bishop, Richard
• Is Part Of: Parasites & vectors. Volume 9:Issue 1(2016)
• Page Start: 1
• Page End: 15
• Publication Date: 2016-12
• Subjects: Ticks -- COI -- 12S rRNA -- ITS2 -- Phylogeography -- Population genetics -- Genetic differentiation -- Genetic markers -- East coast fever; Parasitism -- Periodicals; Parasites -- Periodicals; Vector-pathogen relationships -- Periodicals; Animals as carriers of disease -- Periodicals; Insects as carriers of disease -- Periodicals; 616.96
• DOI: 10.1186/s13071-016-1631-1
• Languages: English
• ISSNs: 1756-3305

Abstract

Abstract Background The ixodid tickRhipicephalus appendiculatus transmits the apicomplexan protozoan parasiteTheileria parva, which causes East coast fever (ECF), the most economically important cattle disease in eastern and southern Africa. Recent analysis of micro- and minisatellite markers showed an absence of geographical and host-associated genetic sub-structuring amongst field populations ofR. appendiculatus in Kenya. To assess further the phylogenetic relationships between field and laboratoryR. appendiculatus tick isolates, this study examined sequence variations at two mitochondrial genes, cytochromec oxidase subunit I (COI) and 12S ribosomal RNA (rRNA), and the nuclear encoded ribosomal internal transcribed spacer 2 (ITS2) of the rRNA gene, respectively. Results The analysis of 332 COI sequences revealed 30 polymorphic sites, which defined 28 haplotypes that were separated into two distinct haplogroups (A and B). Inclusion of previously published haplotypes in our analysis revealed a high degree of phylogenetic complexity never reported before in haplogroup A. Neither haplogroup however, showed any clustering pattern related to either the geographical sampling location, the type of tick sampled (laboratory stocksvs field populations) or the mammalian host species. This finding was supported by the results obtained from the analysis of 12S rDNA sequences. Analysis of molecular variance (AMOVA) indicated that 90.8 % of the total genetic variation was explained by the two haplogroups, providing further support for their genetic divergence. These results were, however, not replicated by the nuclear transcribed ITS2 sequences likely because of recombination between the nuclear genomes maintaining a high level of genetic sequence conservation. Conclusions COI and 12S rDNA are better markers than ITS2 for studying intraspecific diversity. Based on these genes, two major genetic groups ofR. appendiculatus that have gone through a demographic expansion exist in Kenya. The two groups show no phylogeographic structure or correlation with the type of host species from which the ticks were collected, nor to the evolutionary and breeding history of the species. The two lineages may have a wide geographic distribution range in eastern and southern Africa. The findings of this study may have implications for the spread and control ofR. appendiculatus, and indirectly, on the transmission dynamics of ECF.