Characterization of Dicrocoelium chinensis from domestic yaks in Gansu and Sichuan provinces, China, using genetic markers in two mitochondrial genes

Abstract

Dicrocoelium chinensis is commonly known as the “lancet fluke” or “small liver fluke” which lives in the bile ducts and gall bladder of domestic and wild ruminants. In this study, we examined sequence variability in two mitochondrial (mt) genes, namely cytochrome c oxidase subunit 1 (cox1) and NADH dehydrogenase subunit 1 (nad1) genes, among D. chinensis isolated from domestic yaks in Gansu and Sichuan provinces, China. A portion of the cox1 (pcox1) and nad1 (pnad1) genes was amplified by PCR separately from the individual adult D. chinensis, and the amplicons were subjected to sequencing from both directions. The lengths of the sequences of pcox1 and pnad1 were 358 and 458 bp, respectively. The A+T contents of the sequences were 58.94–59.22% for pcox1 and 60.04–60.48% for pnad1, respectively. The intra-specific sequence variations within D. chinensis were 0–0.84% for pcox1 and 0–0.87% for pnad1. The inter-specific sequence differences among members of the examined trematodes were significantly higher, being 22.9–29.3% and 33.6–41.5% for pcox1 and pnad1, respectively. Phylogenetic analysis utilizing combined sequences of pcox1 and pnad1 using Bayesian inference revealed that all of the D. chinensis isolates grouped together with high statistical support. These findings demonstrated the existence of low intra-specific variation in mitochondrial DNA (mtDNA) sequences among the D. chinensis isolates from domestic yaks in China and had implications for studying the molecular epidemiology and population genetics of D. chinensis.