The divergence pattern of Trichinella spiralis isolates from China revealed by mitochondrial and ribosomal markers.

Trichinella spiralis is the main etiological agent of human trichinellosis. In China, trichinellosis remains a serious food-borne parasitic zoonosis and poses a serious threat to human health. However, the genetic structure of Chinese T. spiralis population is still little known. In this study, we used three molecular markers to analyze phylogeographic structure of the Chinese T. spiralis population. A total of 11 T. spiralis isolates were collected from 10 geographical locations in mainland China. The cytochrome c-oxidase gene (COI), large subunit ribosomal DNA (mt-lsrDNA) and 5S ribosomal DNA intergenic spacer region (5S ISR) genes of each isolate was amplified and sequenced. Only four haplotypes were found in these concatenated sequences. Both multimodal frequency distributions of mismatch analysis and the Bayesian skyline plot analysis rejected a possible population expansion of Chinese T. spiralis population. The phylogenetic inference based on neighbor-joining (NJ), maximum parsimony (MP), maximum likelihood (ML) and the Bayesian estimation of divergence times under the uncorrelated log-normal relaxed molecular-clock model suggested that the Chinese T. spiralis isolates started radiating in the late Miocene.