Genetic variability in the three mitochondrial genes among Oesophagostomum asperum isolates from different regions in Shaanxi and Hunan Provinces, China.

The present study examined sequence variations in three mitochondrial DNA (mtDNA) regions, namely, NADH dehydrogenase subunit 5 (nad5), adenosine triphosphate subunit 6 (atp6) and cytochrome c oxidase subunit 3 (cox3), among Oesophagostomum asperum isolates from different regions in Shaanxi and Hunan provinces, China. The lengths for partial sequences of nad5 (pnad5), atp6 (patp6) and cox3 (pcox3) were 427 bp, 381 bp and 337 bp, respectively. The intra-specific sequence variations among all O. asperum samples were 0-2.11%, 0-1.84% and 0-1.48% for pnad5, patp6 and pcox3, respectively, while the inter-specific sequence differences among Oesophagostomum species in pig and small ruminants were 18-21.3% for pnad5, 18.3-24.5% for patp6 and 10.6-13.7% for pcox3. A phylogenetic analysis based on combined sequences of three mtDNA fragments indicated that all O. asperum isolates were grouped in one solid clade, and the Oesophagostomum spp. from pig were located in another clade. However, these mtDNA fragments could not reveal genetic relationships of geographical isolates of O. asperum in China. These results provided valuable information for studying population genetics of Oesophagostomum spp., and for controlling Oesophagostomum infection in animals as well as humans.