title: Characterization of the complete mitochondrial genome of Spirocerca lupi: sequence, gene organization and phylogenetic implications.
abstract: BACKGROUND
  Spirocerca lupi is a life-threating parasitic nematode of dogs that has a cosmopolitan distribution but is most prevalent in tropical and subtropical countries. Despite its veterinary importance in canids, the epidemiology, molecular ecology and population genetics of this parasite still remain unexplored.
  
  
  METHODS
  The complete mitochondrial (mt) genome of S. lupi was amplified in four overlapping long fragments using primers designed based on partial cox1, rrnS, cox2 and nad2 sequences. Phylogenetic re-construction of 13 spirurid species (including S. lupi) was carried out using Bayesian inference (BI) based on concatenated amino acid sequence datasets.
  
  
  RESULTS
  The complete mt genome sequence of S. lupi is 13,780 bp in length, including 12 protein-coding genes, 22 transfer RNA genes and two ribosomal RNA genes, but lacks the atp8 gene. The gene arrangement is identical to that of Thelazia callipaeda (Thelaziidae) and Setaria digitata (Onchocercidae), but distinct from that of Dracunculus medinensis (Dracunculidae) and Heliconema longissimum (Physalopteridae). All genes are transcribed in the same direction and have a nucleotide composition high in A and T. The content of A + T is 73.73% for S. lupi, in accordance with mt genomes of other spirurid nematodes sequenced to date. Phylogenetic analyses using concatenated amino acid sequences of the 12 protein-coding genes by BI showed that the S. lupi (Thelaziidae) is closely related to the families Setariidae and Onchocercidae.
  
  
  CONCLUSIONS
  The present study determined the complete mt genome sequence of S. lupi. These new mt genome dataset should provide novel mtDNA markers for studying the molecular epidemiology and population genetics of this parasite, and should have implications for the molecular diagnosis, prevention and control of spirocercosis in dogs and other canids.
authors: College of Veterinary Medicine, Hunan Agricultural University, Changsha, Hunan Province, 410128, China.
authors: Guo-Hua
authors: GH
authors: Liu
authors: Yan
authors: Y
authors: Wang
authors: Hui-Qun
authors: HQ
authors: Song
authors: Ming-Wei
authors: MW
authors: Li
authors: Lin
authors: L
authors: Ai
authors: Xing-Long
authors: XL
authors: Yu
authors: Xing-Quan
authors: XQ
authors: Zhu
mesh_terms: D000818:Animals; D001483:Base Sequence; D003062:Codon; D017931:DNA Primers / Q000235:genetics; D018509:DNA, Helminth / Q000737:chemistry / Q000235:genetics; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics; D004283:Dog Diseases / Q000469:parasitology*; D004285:Dogs; D023061:Gene Order; D017238:Genes, Helminth / Q000235:genetics*; D054629:Genome, Mitochondrial / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA / Q000662:veterinary; D017205:Spirurida Infections / Q000469:parasitology / Q000662:veterinary*; D013802:Thelazioidea / Q000145:classification / Q000235:genetics*
chemical_list: D003062:Codon; D017931:DNA Primers; D018509:DNA, Helminth; D004272:DNA, Mitochondrial