Analyses of mitochondrial genes reveal two sympatric but genetically divergent lineages of Rhipicephalus appendiculatus in Kenya

Abstract

BackgroundThe ixodid tick Rhipicephalus appendiculatus transmits the apicomplexan protozoan parasite Theileria 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 of R. appendiculatus in Kenya. To assess further the phylogenetic relationships between field and laboratory R. appendiculatus tick isolates, this study examined sequence variations at two mitochondrial genes, cytochrome c oxidase subunit I (COI) and 12S ribosomal RNA (rRNA), and the nuclear encoded ribosomal internal transcribed spacer 2 (ITS2) of the rRNA gene, respectively.ResultsThe 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 stocks vs 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.ConclusionsCOI and 12S rDNA are better markers than ITS2 for studying intraspecific diversity. Based on these genes, two major genetic groups of R. 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 of R. appendiculatus, and indirectly, on the transmission dynamics of ECF.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1631-1) contains supplementary material, which is available to authorized users.

Mitochondrial phylogeography and population structure of the cattle tick Rhipicephalus appendiculatus in the African Great Lakes region

“…Given the suitability of mitochondrial genes to discriminate intraspecific variation in ticks [ 29 , 31 ], we amplified the cox 1 and 12S rRNA gene loci to assess the genetic diversity and phylogenetic relationships of R. appendiculatus populations . A 710 bp fragment of cox 1 gene locus was amplified with the forward primer LCO1490 (5'-GGT CAA CAA ATC ATA AAG ATA TTG G-3') and the reverse primer HC02198 (5'-TAA ACT TCA GGG TGA CCA AAA AAT CA-3') as previously described by Folmer et al [ 40 ]; for the 12S rRNA gene locus we used the primers SR-J-1499 (5'-TAC TAT GTT ACG ACT TAT-3') and SR-N-14594 (5'-AAA CTA GGA TTA GAT ACC C-3') with a fragment size of 380 bp, described in Simon et al [ 41 ].…”

“…Two distinct genetic groups have been described , namely the eastern and the southern African lineages [ 29 ]. More recently, Kanduma et al [ 31 ] found that the two genetic groups are present in Kenya. These evidences show that R. appendiculatus genetic groups may have a wide geographical range, with different ecological preferences and phenology in sub-Saharan Africa [ 32 – 34 ], due to differences in body size [ 35 ] and diapause induction and intensity [ 36 , 37 ].…”

A review of recent research on Theileria parva : Implications for the infection and treatment vaccination method for control of East Coast fever

“…A multilocus VNTR genotyping study of Rhipicephalus appendiculatus from 10 populations within Kenya revealed a lack of genetic structure in the field populations (Kanduma, Mwacharo, Githaka, et al, ; Kanduma, Mwacharo, Meaura, et al, ). This is consistent with T. parva population analyses that revealed a similar situation for T. parva in Kenya (Odongo et al., ).…”

“…It was recently reported that there are two major haplotypes of R. appendiculatus that are sympatric within Kenya (Kanduma, Mwacharo, Githaka, et al., ; Kanduma, Mwacharo, Meaura, et al., ). A similar phenomenon was subsequently described in the Great Lakes region (Amzati et al., ).…”

Comparative population genetic structure of two Ixodidae ticks (Ixodes ovatus and Haemaphysalis flava) in Niigata Prefecture, Japan 

“…In addition to tick population structure studies, genetic studies may also reveal the presence of cryptic species, where morphologically identified individuals might represent more than one species [17]. Previous studies on Rhipecephalus appendiculatus [18], I. holocylus [19] and I. ovatus [20] have revealed the presence of cryptic species based on the clustering of haplotypes in a phylogenetic tree, and concluded that morphological criteria for species differentiation alone are equivocal and that genetic analysis is important. A putative I. ovatus species complex was identified based on the presence of 3 distinct haplotype clusters in both cox1 and 16S rRNA genes; 2 groups in China and one in Japan that included haplotypes from North America [20].…”