Abstract
BackgroundFasciolopsis buski is a zoonotic intestinal fluke infecting humans and pigs, but it has been seriously neglected. It is yet to know whether there is any genetic diversity among F. buski from different geographical locations, particularly in sequences of nuclear ribosomal DNA (rDNA) and mitochondrial (mt) DNA. Therefore, we determined the sequences of partial 18S, the complete internal transcribed spacer (ITS) rDNA and the complete mt genome of F. buski from China, compared the rDNA and mtDNA sequences with those of isolates from India and Vietnam, and assessed the phylogenetic relationships of this fluke and related fasciolid trematodes based on the mtDNA dataset.ResultsThe complete mt genome sequence of F. buski from China is 14,833 bp, with 36 genes, including 12 protein-coding genes (PCGs), 22 tRNA genes, and two rRNA genes (rrnL and rrnS). The AT content of F. buski from China is 65.12%. The gene content and arrangement of the F. buski mt genome is similar to that of Fascioloides magna. Genetic distances between isolates of F. buski from China and India were high (28.2% in mtDNA, 13.2% in ITS-1 and 9.8% in ITS-2) and distinctly higher than the interspecific differences between Fasciola hepatica and Fasciola gigantica. The rDNA and mtDNA datasets for F. buski from China (isolate from pigs) and Vietnam (isolates from humans) were identical. The intergeneric differences in amino acid and nucleotide sequences among the genera Fasciolopsis, Fascioloides and Fasciola ranged between 24.64–25.56% and 26.35–28.46%, respectively.ConclusionsOur results indicate that F. buski from China and India may represent distinct taxa, while F. buski in Vietnam and China represent the same species. These findings might have implications for the implementation of appropriate control strategies in different regions. Further studies are needed to decode mtDNA and rDNA sequences of F. buski from various geographical isolates for the better understanding of the species complex of F. buski.
Highlights
Fasciolopsis buski is a zoonotic intestinal fluke infecting humans and pigs, but it has been seriously neglected
Incomplete sequences of the first and the second internal transcribed spacer (ITS-1 and ITS-2) regions of nuclear ribosomal DNA of F. buski were determined and deposited [15, 19]; the ITS-2 sequences of isolates of F. buski from India and Vietnam differ by 6.7% [18], a divergence that is much larger than that between Fasciola hepatica and Fasciola gigantica (1.7%) [20]
The difference of ITS ribosomal DNA (rDNA) between isolates from Vietnam [EF612477 (ITS-1) and EF612489 (ITS-2)] and India were 2.36% in ITS-1 and 6.75% in ITS-2. These were higher than the interspecific differences between Fa. hepatica and Fa. gigantica (1.2% in ITS-1 and 1.7% in ITS-2) [20], but lower than intergeneric difference between Fas. magna and Fa. hepatica (7.04% in ITS-1, 13.8% in ITS-2) [22]
Summary
Fasciolopsis buski is a zoonotic intestinal fluke infecting humans and pigs, but it has been seriously neglected. We determined the sequences of partial 18S, the complete internal transcribed spacer (ITS) rDNA and the complete mt genome of F. buski from China, compared the rDNA and mtDNA sequences with those of isolates from India and Vietnam, and assessed the phylogenetic relationships of this fluke and related fasciolid trematodes based on the mtDNA dataset. Incomplete sequences of the first and the second internal transcribed spacer (ITS-1 and ITS-2) regions of nuclear ribosomal DNA (rDNA) of F. buski were determined and deposited [15, 19]; the ITS-2 sequences of isolates of F. buski from India and Vietnam differ by 6.7% [18], a divergence that is much larger than that between Fasciola hepatica and Fasciola gigantica (1.7%) [20]. No information exists to illustrate the relationships between isolates of F. buski from India, Vietnam and mainland China, and none of the publications have explained the sequence discrepancies among these F. buski isolates
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