Institute of Biotechnology, Vietnam Academy of Science and Technology, 18. Hoang Quoc Viet Rd,, Cau Giay, Hanoi, Vietnam.
Department of Parasitology, National Institute of Malariology, Parasitology and Entomology, Luong The Vinh Rd,, Thanh Xuan, Hanoi, Vietnam.
Parasit Vectors. 2017 Jan 9;10(1):17. doi: 10.1186/s13071-017-1968-0.
Heterophyidiasis is now a major public health threat in many tropical countries. Species in the trematode family Heterophyidae infecting humans include Centrocestus formosanus, Haplorchis pumilio, H. taichui, H. yokogawai, Procerovum varium and Stellantchasmus falcatus. For molecular phylogenetic and systematic studies on trematodes, we need more prospective markers for taxonomic identification and classification. This study provides near-complete ribosomal transcription units (rTU) from Haplorchis pumilio and H. taichui and demonstrates the use of 28S rDNA sequences for identification and phylogenetic analysis.
The near-complete ribosomal transcription units (rTU), consisting of 18S, ITS1, 5.8S, ITS2 and 28S rRNA genes and spacers, from H. pumilio and H. taichui from human hosts in Vietnam, were determined and annotated. Sequence analysis revealed tandem repetitive elements in ITS1 in H. pumilio and in ITS2 in H. taichui. A phylogenetic tree inferred from 28S rDNA sequences of 40 trematode strains/species, including 14 Vietnamese heterophyid individuals, clearly confirmed the status of each of the Vietnamese species: Centrocestus formosanus, Haplorchis pumilio, H. taichui, H. yokogawai, Procerovum varium and Stellantchasmus falcatus. However, the family Heterophyidae was clearly not monophyletic, with some genera apparently allied with other families within the superfamily Opisthorchioidea (i.e. Cryptogonimidae and Opisthorchiidae). These families and their constituent genera require substantial re-evaluation using a combination of morphological and molecular data. Our new molecular data will assist in such studies.
The 28S rDNA sequences are conserved among individuals within a species but varied between genera. Based on analysis of 40 28S rDNA sequences representing 19 species in the superfamily Opisthorchioidea and an outgroup taxon (Alaria alata, family Diplostomidae), six common human pathogenic heterophyids were identified and clearly resolved. The phylogenetic tree inferred from these sequences again confirmed anomalies in molecular placement of some members of the family Heterophyidae and demonstrates the need for reappraisal of the entire superfamily Opisthorchioidea. The new sequences provided here supplement those already available in public databases and add to the array of molecular tools that can be used for the diagnosis of heterophyid species in human and animal infections.
旋毛虫病现在是许多热带国家的主要公共卫生威胁。感染人类的异形科异形吸虫包括台湾异形吸虫、哈氏异形吸虫、台湾异形吸虫、横川异形吸虫、普氏异尖线虫和尖形异形吸虫。为了进行吸虫的分子系统发育和系统研究，我们需要更多的分类鉴定的前瞻性标记物。本研究提供了来自越南人体的哈氏异形吸虫和台湾异形吸虫的近完整核糖体转录单位（rTU），并展示了 28S rDNA 序列在鉴定和系统发育分析中的应用。
从来自越南人体的哈氏异形吸虫和台湾异形吸虫的近完整核糖体转录单位（rTU）中，确定并注释了由 18S、ITS1、5.8S、ITS2 和 28S rRNA 基因和间隔区组成的序列。序列分析显示哈氏异形吸虫的 ITS1 中存在串联重复元件，而台湾异形吸虫的 ITS2 中存在串联重复元件。从包括 14 种越南异形吸虫在内的 40 种吸虫株/种的 28S rDNA 序列推断出的系统发育树清楚地证实了每一种越南物种的地位：台湾异形吸虫、哈氏异形吸虫、台湾异形吸虫、横川异形吸虫、普氏异尖线虫和尖形异形吸虫。然而，异形科显然不是单系的，有些属显然与 Opisthorchioidea 超科中的其他科（即 Cryptogonimidae 和 Opisthorchiidae）有关。这些科及其组成属需要使用形态学和分子数据进行大量重新评估。我们的新分子数据将有助于此类研究。
28S rDNA 序列在一个物种内的个体之间是保守的，但在属之间是不同的。基于对代表 Opisthorchioidea 超科的 19 个种的 40 个 28S rDNA 序列和一个外群分类单元（Alaria alata，双腔科）的分析，鉴定并明确区分了六种常见的人类致病异形吸虫。从这些序列推断出的系统发育树再次证实了异形科某些成员的分子位置异常，并表明需要重新评估整个 Opisthorchioidea 超科。这里提供的新序列补充了已在公共数据库中提供的序列，并增加了可用于诊断人类和动物感染中异形种的分子工具的种类。
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