Phylogeography and population differentiation in Hepatozoon canis (Apicomplexa: Hepatozoidae) reveal expansion and gene flow in world populations

Abstract

Background Hepatozoon canis is a protozoan transmitted to dogs and other wild carnivores by the ingestion of ticks containing mature oocysts and is considered the principal cause of canine hepatozoonosis in the world. Here, we examined ribosomal RNA 18S gene sequence variation to determine the genetic differences and phylogeographic diversity of H. canis from various geographical areas around the world. Methods We used 550 publicly available sequences of H. canis from 46 countries to assess haplotype relationships, geographical structure, genetic diversity indices, and relationships among populations. We performed neutrality tests and pairwise comparisons of fixation index (FST) values between groups and pairwise comparisons of FST values between populations. To determine whether populations are structured, analyses of molecular variance (AMOVAs) and spatial analysis of molecular variance (SAMOVA) were performed. Results The dataset of H. canis yielded 76 haplotypes. Differentiation among populations indicated that there is no phylogeographical structure (GST = 0.302 ± 0.0475). Moreover, when samples were grouped by continents a significant FST was obtained, meaning that populations were genetically differentiated. The AMOVA showed that 57.4% of the genetic variation was explained by differences within populations when all locations were treated as a single group and revealed that there is no population structure when populations are grouped into two, three, and four groups (FCT, p > 0.05), suggesting that dispersal between populations is high. SAMOVA revealed significant FCT values for groups K = 5. The Tajima’s D and Fu’s Fs show that populations have undergone recent expansion, and the mismatch distribution analysis showed population expansion (multimodal distribution). Conclusions The current molecular data confirmed that H. canis does not show phylogeographic or population structure. The haplotypes exhibit low genetic differentiation, suggesting a recent expansion due to gene flow among populations. These results provide pivotal information required for future detailed population genetic analysis or to establish control strategies of this parasite. Graphical abstract

Analysis of genetic diversity and population structure of Babesia gibsoni

“…These results were much lower than that of H . canis ( 27 ), but similar to Plasmodium knowlesi ( 55 ) and Plasmodium vivax ( 56 ). Haplotype analysis indicated that the genetic diversity was observed with high haplotype diversity in Asian countries except for Bangladesh and India.…”

“…The average haplotype diversity of 0.474 and 0.473 were in Asia and the three continents, respectively, which was lower in comparison with other protozoa such as H . canis ( 27 ) and P. knowlesi ( 55 ). Population size is an essential factor in affecting the genetic diversity, therefore, lower haplotype diversity seemed to correlate with a small effective population size in this study.…”

“…Understanding the genetic differentiation and population structure of protozoan parasites will be helpful to evaluate their evolution, spatiotemporal dynamics and genetic exchange, as well as to formulate the effective strategies to prevent the transmission of pathogens ( 26 ). Molecular markers such as 18S rRNA, mitochondrial DNA, microsatellite loci and single nucleotide polymorphisms are often employed to explore the genetic variation and provide the information on reproductive modes and molecular sequences obtained from samples to explain the evolutionary history of populations ( 27 ). Several genetic diversity studies of tick-transmitted hemoprotozoan parasites have currently been described, including Babesia bovis, Babesia ovis, Hepatozoon canis, Theileria annulata , and Theileria parva ( 27 – 31 ).…”

“…Molecular markers such as 18S rRNA, mitochondrial DNA, microsatellite loci and single nucleotide polymorphisms are often employed to explore the genetic variation and provide the information on reproductive modes and molecular sequences obtained from samples to explain the evolutionary history of populations ( 27 ). Several genetic diversity studies of tick-transmitted hemoprotozoan parasites have currently been described, including Babesia bovis, Babesia ovis, Hepatozoon canis, Theileria annulata , and Theileria parva ( 27 – 31 ). These studies demonstrated that high genetic diversity was detected in B. bovis, B. ovis, T. annulata , and T. parva populations ( 28 – 31 ).…”

“…A high gene flow was found between H . canis populations originating from distant continents ( 27 ). The phylogenetic and population differentiation of Babesia spp., which can parasitize cattle, sheep and horses, were explained by previous studies ( 28 , 29 , 32 ).…”