Genetic diversity in Echinococcus shiquicus from the plateau pika (Ochotona curzoniae) in Darlag County, Qinghai, China

Abstract The metacestode of Echinococcus shiquicus has been recorded previously in the lung and liver of its intermediate host, the plateau pika ( Ochotona curzoniae ), but there is limited information regarding other organ sites. There is also limited evidence of intra-specific genetic variation within E . shiquicus . A PCR-amplified mitochondrial (mt) nad 1 gene fragment (approximately 1400 bp in size), with unique Eco RI and Ssp I restriction sites, was used to distinguish cysts or cyst-like lesions of E . shiquicus from E . multilocularis . Then, the complete mt nad 1 and cox 1 genes for the E . shiquicus isolates were amplified and sequenced. Phylogenetic tree and haplotype network analyses for the isolates were then generated based on a concatenated dataset of the nad 1 and cox 1 genes using the neighbour-joining (NJ) method and TCS1.21 software. Nineteen of eighty trapped pikas were found to harbor cysts (71 in total) when dissected at the survey site. Seventeen animals had cysts (fertile) present only in the lungs, one animal had fertile cysts in the lungs and spleen, and one individual had an infertile kidney cyst. Restriction endonuclease analysis of a fragment of the nad 1 gene indicated all the cysts were due to E . shiquicus . Genetic diversity analysis revealed that the nad 1 and cox 1 genes varied by 0.1–1.2% and 0.1–1.0%, respectively. Haplotype network analysis of the concatenated nad 1 and cox 1 sequences of the isolates showed they were classified into at least 6 haplotypes, and different haplotype percentages ranged from 4.2% to 29.6%. Although, high haplotype diversity was evident in the study area, the complete nad 1 and cox 1 gene sequences obtained indicated that all samples represented isolates of E . shiquicus . The study has also provided a new PCR-restriction endonuclease-based method to rapidly distinguish E . shiquicus from E . multilocularis which provides a useful tool for epidemiological investigations where the two species overlap.