Abstract
Background Schistosoma japonicum still causes severe parasitic disease in mainland China, but mainly in areas along the Yangtze River. However, the genetic diversity in populations of S. japonicum has not been well understood across its geographical distribution, and such data may provide insights into the epidemiology and possible control strategies for schistosomiasis.Methodology/Principal FindingsIn this study infected Oncomelania snails were collected from areas in the middle and lower (ML) reaches of the Yangtze River, including Hubei, Hunan, Anhui, Jiangxi and Jiangsu provinces, and in the upper reaches of the river, including Sichuan and Yunnan provinces in southwest (SW) China. The adult parasites obtained from experimentally infected mice using isolated cercariae were sequenced individually for several fragments of mitochondrial regions, including Cytb-ND4L-ND4, 16S-12S and ND1. Populations in the ML reaches exhibited a relatively high level of diversity in nucleotides and haplotypes, whereas a low level was observed for populations in the SW, using either each single fragment or the combined sequence of the three fragments. Pairwise analyses of F-statistics (Fst) revealed a significant genetic difference between populations in the ML reaches and those in the SW, with limited gene flow and no shared haplotypes in between. It is rather obvious that genetic diversity in the populations of S. japonicum was significantly correlated with the geographical distance, and the geographical separation/isolation was considered to be the major factor accounting for the observed difference between populations in the ML reaches and those in the SW in China.Conclusions S. japonicum in mainland China exhibits a high degree of genetic diversity, with a similar pattern of genetic diversity as observed in the intermediate host snails in the same region in China.
Highlights
Schistosomiasis is one of the most neglected tropical diseases, with six species in the Schistosoma still infecting more than 200 million people in the world [1,2,3]
S. japonicum in mainland China exhibits a high degree of genetic diversity, with a similar pattern of genetic diversity as observed in the intermediate host snails in the same region in China
Collection of parasite specimens The intermediate host, Oncomelania hupensis, from 18 localities of 7 schistosomiasis endemic provinces in mainland China, including Hubei, Hunan, Anhui, Jiangxi, Jiangsu provinces in the middle and lower (ML) reaches of Yangtze River, and Sichuan and Yunnan provinces which are in the higher reaches of the river in SW China, but separated from the ML reaches by mountain ranges (Fig. 1 and Table 1), were collected and transported to laboratory from October 2005 to October 2006
Summary
Schistosomiasis is one of the most neglected tropical diseases, with six species in the Schistosoma still infecting more than 200 million people in the world [1,2,3]. The drastic pathogenesis, the number of reservoir hosts involved in epidemiology and the vast endemic areas of schistosomiasis japonica have inevitably resulted in a less investigated status for S. japonicum in respect with its genetic diversity, host immune response etc. The genetic diversity in populations of S. japonicum has not been well understood across its geographical distribution, and such data may provide insights into the epidemiology and possible control strategies for schistosomiasis
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