Abstract
BackgroundSparganosis caused by invasion of the plerocercoid larvae (spargana) of Spirometra erinaceieuropaei have increased in recent years in China. However, the population genetic structure regarding this parasite is still unclear. In this study, we used the sequences of two mitochondrial genes cytochrome b (cytb) and cytochrome c oxidase subunit I (cox1) to analyze genetic variation and phylogeographic structure of the S. erinaceieuropaei populations.Methodology/Principal FindingsA total of 88 S. erinaceieuropaei isolates were collected from naturally infected frogs in 14 geographical locations of China. The complete cytb and cox1 genes of each sample was amplified and sequenced. Total 61 haplotypes were found in these 88 concatenated sequences. Each sampled population and the total population have high haplotype diversity (Hd), accompanied by very low nucleotide diversity (Pi). Phylogenetic analyses of haplotypes revealed two distinct clades (HeN+HuN+GZ-AS clade and GX+HN+GZ-GY clade) corresponding two sub-networks yielded by the median-joining network. Pairwise F ST values supported great genetic differentiation between S. erinaceieuropaei populations. Both negative Fu’s F S value of neutrality tests and unimodal curve of mismatch distribution analyses supported demographic population expansion in the HeN+HuN+GZ-AS clade. The BEAST analysis showed that the divergence time between the two clades took place in the early Pleistocene (1.16 Myr), and by Bayesian skyline plot (BSP) an expansion occurred after about 0.3 Myr ago.Conclusions S. erinaceieuropaei from central and southern China has significant phylogeographic structure, and climatic oscillations during glacial periods in the Quaternary may affect the demography and diversification of this species.
Highlights
Spirometra erinaceieuropaei (Cestoidea: Pseudophyllidea: Diphyllobothriidae) is one of the most important species of tapeworms [1]
China has the largest number of sparganosis cases in the world since 1999, with a total of approximately 1,000 instances of human sparganosis being reported in 27 out of 34 provinces, autonomous regions, or municipal districts [7]
The aim of this study was to investigate the genetic variability, population structure and divergence pattern among S. erinaceieuropaei populations from central and southern China based on cytb and cox1 genes of mitochondrial DNA
Summary
Spirometra erinaceieuropaei (Cestoidea: Pseudophyllidea: Diphyllobothriidae) is one of the most important species of tapeworms [1]. Its plerocercoid larvae (spargana) can lodge in the subcutaneous tissues and sometimes invade the abdominal cavity, eye, and central nervous system of humans causing a serious parasitic zoonosis known as sparganosis [2]. Human infection results mainly from ingesting raw flesh of frogs and snakes infected with the plerocercoids, drinking raw water contaminated with cyclops harboring procercoids, or placing frog or snake flesh as poultice on open wound for treatment of skin ulcers or eye inflammations [3,4]. China has the largest number of sparganosis cases in the world since 1999, with a total of approximately 1,000 instances of human sparganosis being reported in 27 out of 34 provinces, autonomous regions, or municipal districts [7]. The local cases have increased in recent years and sparganosis has even been termed as emerging enzootic diseases in several districts of China [8,9].
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