Studies On Genetic Diversity And Molecular Identification For Oesopha Gostomum Asperum And Oesopha Gostomum Columbianum

Oesophagostomum spp. parasitize in large intestines of livestock, sometimes found inhuman, are called “node worms” due to the yellowish nodules formed in the intestinal wall bythe larvae. O. columbianun, O. asperum, O. venulosum, O. kansuensis were considered thepredominant species in sheep and goats. O.columbianum and O. asperum have beenconsidered as two of most harmful species in sheep and goats, can lead to anorexia, anaemia,diarrhea, poor growth, and even death in animals with serious infection. Oesophagostomumspp. not only cause great economic losses to the livestock industry, but also are of greatsignificance to public health. The research to genetic variation and population structure ofOesophagostomum has implication on the prevention and control of oesophagostomiasis.1The internal transcribed spacers (ITS) of ribosomal DNA (rDNA) of O. asperum and O.columbianum were amplified and sequenced. The ITS-1,5.8S and ITS-2rDNA sequences ofO. asperum were374bp,153bp and259bp in length, respectively, and the correspondingsequences of O. columbianum were259bp,153bp and218bp in length, respectively.Sequence differences in the ITS-1and ITS-2rDNA between the two Oesophagostomumspecies were9.5%～10.2%and12.7%～13.9%, respectively. Based on genetic markers in theITS rDNA, an effective polymerase chain reaction (PCR) approach was developed todifferentiate O. columbianum from O. asperum with a sensitivity of0.2ng/ml DNA. Sinceaccurate characterization of parasites at different taxonomic levels is essential for populationgenetic studies and control of parasitosis, the present findings have important implications forstudying epidemiology, taxonomy and population biology.2The sequence variations in three mitochondrial DNA regions, namely cytochrome coxidase subunit3(cox3), NADH dehydrogenase subunits5(nad5) and adenosine triphosphatesubunit6(atp6) for O. asperum were examined, and their phylogenetic relationships werere-constructed. A portion of the cox3gene (pcox3), a portion of the nad5gene and atp6gene(pnad5and p atp6) were amplified by PCR, and the amplicons were subjected to directsequencing, revealed that the lengths of partial sequences of nad5(pnad5), atp6(patp6) andcox3(pcox3) were427bp,381bp and337bp, respectively. The intra-specific sequence variations among all O. asperum samples were0～2.11%,0～1.84%and0～1.48%forpnad5, patp6and pcox3, respectively, while the inter-specific sequence differences amongOesophagostomum species in swine and small ruminants were18%～21.3%for pnad5,18.3%～24.5%for patp6and10.6%～13.7%for pcox3. Phylogenetic study based oncombined sequences of three mtDNA fragments indicated that all O. asperum isolates weregrouped in one solid clade, and Oesophagostomum spp. from swine were located in anotherclade. These results provided valuable information for studying population genetics ofOesophagostomum spp.3We sequenced the complete mitochondrial (mt) genomes of O. asperum and O.columbianum in goats and sheep, and its gene content, arrangement and composition werecompared with O. dentatum and O. quadrispinulatum in swine. The complete mt genomes ofO. asperum and O. columbianum were13,672bp and13,561bp in size, respectively. Bothmt genomes are circular, and consist of36genes, including12genes coding for proteins,2genes for rRNA, and22genes for tRNA. The gene content and arrangement are identical tothat of O. dentatum and O. quadrispinulatum. Phylogenetic analysis of O. asperum and O.columbianum with other representative Strongylida nematodes using Bayesian inference (BI)based on concatenated amino acid sequences of12protein-coding genes, revealed thatOesophagostomum is closely related to Chabertia ovina, indicating Oesophagostomum andChabertia are closely related two nematode genera, supporting previous classification basedon morphological features. The availability of the full mtDNA sequences of O. asperum andO. columbianum provides novel genetic markers for studying the population genetics, andmolecular biology of O. asperum and O. columbianum in sheep and other animals.The present study examined the genetic variations and population structure of O. asperumand O. columbianum, based on ITS, mitochondrial partial genes and complete genomes. Theresults were able to reflect the genetic variability and population structure of O. asperum andO. columbianum in mainland Chain, and have implications for the prevention and control ofO. asperum and O. columbianum in different regions of China.