title: Complete mitochondrial genomes of the 'intermediate form' of Fasciola and Fasciola gigantica, and their comparison with F. hepatica.
abstract: BACKGROUND
  Fascioliasis is an important and neglected disease of humans and other mammals, caused by trematodes of the genus Fasciola. Fasciola hepatica and F. gigantica are valid species that infect humans and animals, but the specific status of Fasciola sp. ('intermediate form') is unclear.
  
  
  METHODS
  Single specimens inferred to represent Fasciola sp. ('intermediate form'; Heilongjiang) and F. gigantica (Guangxi) from China were genetically identified and characterized using PCR-based sequencing of the first and second internal transcribed spacer regions of nuclear ribosomal DNA. The complete mitochondrial (mt) genomes of these representative specimens were then sequenced. The relationships of these specimens with selected members of the Trematoda were assessed by phylogenetic analysis of concatenated amino acid sequence datasets by Bayesian inference (BI).
  
  
  RESULTS
  The complete mt genomes of representatives of Fasciola sp. and F. gigantica were 14,453 bp and 14,478 bp in size, respectively. Both mt genomes contain 12 protein-coding genes, 22 transfer RNA genes and two ribosomal RNA genes, but lack an atp8 gene. All protein-coding genes are transcribed in the same direction, and the gene order in both mt genomes is the same as that published for F. hepatica. Phylogenetic analysis of the concatenated amino acid sequence data for all 12 protein-coding genes showed that the specimen of Fasciola sp. was more closely related to F. gigantica than to F. hepatica.
  
  
  CONCLUSIONS
  The mt genomes characterized here provide a rich source of markers, which can be used in combination with nuclear markers and imaging techniques, for future comparative studies of the biology of Fasciola sp. from China and other countries.
authors.forename: Guo-Hua
authors.initials: GH
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province, PR China. robinbg@unimelb.edu.au.
authors.forename: Robin B
authors.initials: RB
authors.lastname: Gasser
authors.forename: Neil D
authors.initials: ND
authors.lastname: Young
authors.forename: Hui-Qun
authors.initials: HQ
authors.lastname: Song
authors.forename: Lin
authors.initials: L
authors.lastname: Ai
authors.forename: Xing-Quan
authors.initials: XQ
authors.lastname: Zhu
mesh_terms: D000818:Animals; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D005209:Fasciola / Q000235:genetics*; D014644:Genetic Variation; D054629:Genome, Mitochondrial / Q000235:genetics*; D013045:Species Specificity
chemical_list: D021903:DNA, Ribosomal Spacer