Mitochondrial genomes of human helminths and their use as markers in population genetics and phylogeny.
ABSTRACT To date, over 100 complete metazoan mitochondrial (mt) genomes of different phyla have been reported. Here, we briefly summarise mt gene organisation in the Metazoa and review what is known of the mt genomes of nematodes and flatworms parasitic in humans. The availability of complete or almost complete mtDNA sequences for several parasitic helminths provides a rich source of genetic markers for phylogenetic analysis and study of genetic variability in helminth groups. Examples of the application of mtDNA in studies on Ascaris, Onchocerca, Schistosoma, Fasciola, Paragonimus, Echinostoma, Echinococcus and Taenia are described.
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ABSTRACT: BACKGROUND: Dictyocaulus species are strongylid nematodes of major veterinary significance in ruminants, such as cattle and cervids, and cause serious bronchitis or pneumonia (dictyocaulosis or "husk"). There has been ongoing controversy surrounding the validity of some Dictyocaulus species and their host specificity. Here, we sequenced and characterized the mitochondrial (mt) genomes of Dictyocaulus viviparus (from Bos taurus) with Dictyocaulus sp. cf. eckerti from red deer (Cervus elaphus), used mt datasets to assess the genetic relationship between these and related parasites, and predicted markers for future population genetic or molecular epidemiological studies. METHODS: The mt genomes were amplified from single adult males of D. viviparus and Dictyocaulus sp. cf. eckerti (from red deer) by long-PCR, sequenced using 454-technology and annotated using bioinformatic tools. Amino acid sequences inferred from individual genes of each of the two mt genomes were compared, concatenated and subjected to phylogenetic analysis using Bayesian inference (BI), also employing data for other strongylids for comparative purposes. RESULTS: The circular mt genomes were 13,310 bp (D. viviparus) and 13,296 bp (Dictyocaulus sp. cf. eckerti) in size, and each contained 12 protein-encoding, 22 transfer RNA and 2 ribosomal RNA genes, consistent with other strongylid nematodes sequenced to date. Sliding window analysis identified genes with high or low levels of nucleotide diversity between the mt genomes. At the predicted mt proteomic level, there was an overall sequence difference of 34.5% between D. viviparus and Dictyocaulus sp. cf. eckerti, and amino acid sequence variation within each species was usually much lower than differences between species. Phylogenetic analysis of the concatenated amino acid sequence data for all 12 mt proteins showed that both D. viviparus and Dictyocaulus sp. cf. eckerti were closely related, and grouped to the exclusion of selected members of the superfamilies Metastrongyloidea, Trichostrongyloidea, Ancylostomatoidea and Strongyloidea. CONCLUSIONS: Consistent with previous findings for nuclear ribosomal DNA sequence data, the present analyses indicate that Dictyocaulus sp. cf. eckerti (red deer) and D. viviparus are separate species. Barcodes in the two mt genomes and proteomes should serve as markers for future studies of the population genetics and/or epidemiology of these and related species of Dictyocaulus.Parasites & Vectors 10/2012; 5(1):241. · 3.25 Impact Factor
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ABSTRACT: Adult tapeworms of the genus Echinococcus (family Taeniidae) occur in the small intestines of carnivorous definitive hosts and are transmitted to particular intermediate mammalian hosts, in which they develop as fluid-filled larvae (cysts) in internal organs (usually lung and liver), causing the disease echinococcosis. Echinococcus species are of major medical importance and also cause losses to the meat and livestock industries, mainly due to the condemnation of infected offal. Decisions regarding the treatment and control of echinococcosis rely on the accurate identification of species and population variants (strains). Conventional, phenetic methods for specific identification have some significant limitations. Despite advances in the development of molecular tools, there has been limited application of mutation scanning methods to species of Echinococcus. Here, we briefly review key genetic markers used for the identification of Echinococcus species and techniques for the analysis of genetic variation within and among populations, and the diagnosis of echinococcosis. We also discuss the benefits of utilizing mutation scanning approaches to elucidate the population genetics and epidemiology of Echinococcus species. These benefits are likely to become more evident following the complete characterization of the genomes of E. granulosus and E. multilocularis.Electrophoresis 07/2013; 34(13):1852-62. · 3.26 Impact Factor
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ABSTRACT: Taenia multiceps is a widely distributed zoonotic tapeworm of canids. The larval stage of the parasite (Coenurus) occurs in sheep, goat and cattle and has been rarely reported from humans. This study investigated genetic variability of two mitochondrial genes in 102 isolates of T. multiceps. Metacestodes were collected from brains and hearts of sheep in Tehran and Qom provinces of Iran. DNA of each isolate was extracted and used for PCR amplification of cytochrome c oxidase subunit I (CO1) and 12S ribosomal DNA (12S rRNA) genes. All amplicons were sequenced and the sequence data were analyzed using NCBI Blast and BioEdit. Phylogenetic trees and pairwise calculations were obtained by using Mega5 software. In total 7 and 25 representative haplotypes were differentiated for CO1 and 12S rRNA genes, respectively. For CO1 sequences 11 segregation sites within 7 haplotypes were observed. For 12S rRNA sequences a total of 32 segregation sites were observed in 25 haplotypes. CO1 gene displayed lower diversity than 12S rRNA gene with an overall nucleotide variation of 3.0% for CO1 vs. 7.2% for 12S rRNA. Pairwise comparisons among 7 haplotypes in CO1 and 12S rRNA genes showed the level of nucleotide differences 0.3-2.5% and 0.2-4.0%, respectively. A high degree of genetic variation was found in the isolates of T. multiceps in Iran. Additional molecular studies are required on the parasite from other intermediate hosts.Veterinary Parasitology 07/2013; · 2.38 Impact Factor