Abstract
BackgroundFascioliasis is an important and neglected disease of humans and other mammals, caused by trematodes of the genus Fasciola. Fasciola hepatica and F. gigantica are valid species that infect humans and animals, but the specific status of Fasciola sp. (‘intermediate form’) is unclear.MethodsSingle specimens inferred to represent Fasciola sp. (‘intermediate form’; Heilongjiang) and F. gigantica (Guangxi) from China were genetically identified and characterized using PCR-based sequencing of the first and second internal transcribed spacer regions of nuclear ribosomal DNA. The complete mitochondrial (mt) genomes of these representative specimens were then sequenced. The relationships of these specimens with selected members of the Trematoda were assessed by phylogenetic analysis of concatenated amino acid sequence datasets by Bayesian inference (BI).ResultsThe complete mt genomes of representatives of Fasciola sp. and F. gigantica were 14,453 bp and 14,478 bp in size, respectively. Both mt genomes contain 12 protein-coding genes, 22 transfer RNA genes and two ribosomal RNA genes, but lack an atp8 gene. All protein-coding genes are transcribed in the same direction, and the gene order in both mt genomes is the same as that published for F. hepatica. Phylogenetic analysis of the concatenated amino acid sequence data for all 12 protein-coding genes showed that the specimen of Fasciola sp. was more closely related to F. gigantica than to F. hepatica.ConclusionsThe mt genomes characterized here provide a rich source of markers, which can be used in combination with nuclear markers and imaging techniques, for future comparative studies of the biology of Fasciola sp. from China and other countries.
Highlights
Fascioliasis is an important and neglected disease of humans and other mammals, caused by trematodes of the genus Fasciola
KF543341) of the specimen of Fasciola sp. from Heilongjiang province were the same as that of an ‘intermediate form’ of Fasciola from China (AJ628428, AJ557570 and AJ557571) reported previously [11,12], which is characterized by polymorphic positions at 10 positions in ITS-1 and ITS-2 (Additional file 1: Figure S1; Table 2)
Based on these key polymorphic positions, this specimen of Fasciola sp. from China was inferred to be a hybrid between F. gigantica and F. hepatica
Summary
Fascioliasis is an important and neglected disease of humans and other mammals, caused by trematodes of the genus Fasciola. The Fasciolidae is a family of flatworms and includes the genus Fasciola Both F. hepatica and F. gigantica, which commonly infect livestock animals and humans (as definitive hosts), are recognized as valid species [8]. The accurate identification of species and genetic variants is relevant in relation to studying their biology, epidemiology and ecology, and has applied implications for the diagnosis of infections. Morphological features, such as body shape and perimeter as well as length/ width ratio, are used to identify adult worms of Fasciola [9]. Such phenotypic criteria are unreliable for specific identification and differentiation, because of considerable variation and/or overlap in measurements between F. hepatica and F. gigantica [10]
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