Genetic diversity of nuclear ITS1-5.8S-ITS2 rDNA sequence in Clonorchis sinensis Cobbold, 1875 (Trematoda: Opisthorchidae) from the Russian Far East.
ABSTRACT The present study examined the molecular organisation and sequence variation in the nuclear ribosomal DNA (rDNA) region, including the two internal transcribed spacers (ITS1 and ITS2) and the 5.8S gene of the Clonorchis sinensis from the Russian Far East. The relevant sequences from other parts of this species' area were downloaded from GenBank. The results showed 100% identity for all investigated 5.8S-ITS2 rDNA sequences. In contrast, two levels of intraspecific variations were revealed in the complete ITS1 sequences. The intra-genomic variation resulted from a C/T polymorphism in a single position. The inter-individual differences between the ITS1 sequences were both due to nucleotide and size polymorphisms resulting from a varying number of five-nucleotide repeats and followed by two ITS1 length variants. These variant frequencies correlate with the clonorchiasis level in some geographical localities. ITS1 differences, both in the mutation profile and mutation localisation, were revealed between northern and southern geographical samples. The presence of GC boxes that are identical to known regulatory motifs in eukaryotes was detected within the ITS1 sub-repeats. The predicted secondary structures for ITS1 consist of two large branches, one of which was invariable, while another depended on ITS1 length. The predicted secondary structure for ITS2 includes four helices around the core. The main differences between C. sinensis and other opisthorchids were localised on the tops of helices 2, 3, and 4. A phylogenetic MST reconstruction subdivided all ITS1 sequences into two well differentiated clusters, each with the major widespread ribotype, and showed that ribotype diversity in both Russia and Korea is much lower than in China. The results obtained demonstrate the feasibility of complete ITS1 sequences in C. sinensis population genetics and can be considered as a basis for further studies of the parasite infection because they may help to elucidate the molecular mechanisms of pathogen evolution and adaptation.
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ABSTRACT: Clonorchis sinensis, Opisthorchis felineus and Opisthorchis viverrini are the three most important liver flukes involved in human health, infecting more than 45 million people worldwide. Both C. sinensis and O. viverrini, and possibly O. felineus, can induce human cholangiocarcinoma as well as inducing other hepatobiliary pathology. Although the life cycles of all three species are similar, only that of O. felineus in Europe remains predominantly zoonotic, while O. felineus in Asia and C. sinensis have a stronger mixture of zoonotic and anthroponotic components in their life cycles. Opisthorchis viverrini from the Mekong area of southeastern Asia is predominantly anthroponotic. Here we discuss the comparative epidemiology of these three taxa comparing in detail the use of first, second and final animal hosts, and consider the potential role of humans in spreading these pathogens. In addition we discuss the genetic structure of all three species in relation to potentially cryptic species complexes.International journal for parasitology 08/2013; · 3.39 Impact Factor
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ABSTRACT: Opisthorchis felineus or Siberian liver fluke is a trematode parasite (Opisthorchiidae) that infects the hepato-biliary system of humans and other mammals. Despite its public health significance, this wide-spread Eurasian species is one of the most poorly studied human liver flukes and nothing is known about its population genetic structure and demographic history. In this paper, we attempt to fill this gap for the first time and to explore the genetic diversity in O. felineus populations from Eastern Europe (Ukraine, European part of Russia), Northern Asia (Siberia) and Central Asia (Northern Kazakhstan). Analysis of marker DNA fragments from O. felineus mitochondrial cytochrome c oxidase subunit 1 and 3 (cox1, cox3) and nuclear rDNA internal transcribed spacer 1 (ITS1) sequences revealed that genetic diversity is very low across the large geographic range of this species. Microevolutionary processes in populations of trematodes may well be influenced by their peculiar biology. Nevertheless, we suggest that lack of population genetics structure observed in O. felineus can be primarily explained by the Pleistocene glacial events and subsequent sudden population growth from a very limited group of founders. Rapid range expansion of O. felineus through Asian and European territories after severe bottleneck points to a high dispersal potential of this trematode species.PLoS ONE 01/2013; 8(4):e62453. · 3.73 Impact Factor
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ABSTRACT: Clonorchis sinensis, an ancient parasite that infects a number of piscivorous mammals, attracts significant public health interest due to zoonotic exposure risks in Asia. The available studies are insufficient to reflect the prevalence, geographic distribution, and intraspecific genetic diversity of C. sinensis in endemic areas. Here, a multilocus analysis based on eight genes (ITS1, act, tub, ef-1a, cox1, cox3, nad4 and nad5 [4.986 kb]) was employed to explore the intra-species genetic construction of C. sinensis in China. Two hundred and fifty-six C. sinensis isolates were obtained from environmental reservoirs from 17 provinces of China. A total of 254 recognized Multilocus Types (MSTs) showed high diversity among these isolates using multilocus analysis. The comparison analysis of nuclear and mitochondrial phylogeny supports separate clusters in a nuclear dendrogram. Genetic differentiation analysis of three clusters (A, B, and C) showed low divergence within populations. Most isolates from clusters B and C are geographically limited to central China, while cluster A is extraordinarily genetically diverse. Further genetic analyses between different geographic distributions, water bodies and hosts support the low population divergence. The latter haplotype analyses were consistent with the phylogenetic and genetic differentiation results. A recombination network based on concatenated sequences showed a concentrated linkage recombination population in cox1, cox3, nad4 and nad5, with spatial structuring in ITS1. Coupled with the history record and archaeological evidence of C. sinensis infection in mummified desiccated feces, these data point to an ancient origin of C. sinensis in China. In conclusion, we present a likely phylogenetic structure of the C. sinensis population in mainland China, highlighting its possible tendency for biogeographic expansion. Meanwhile, ITS1 was found to be an effective marker for tracking C. sinensis infection worldwide. Thus, the present study improves our understanding of the global epidemiology and evolution of C. sinensis.PLoS ONE 01/2013; 8(6):e67006. · 3.73 Impact Factor