Department of Public Health and Infectious Diseases, Section of Parasitology, Sapienza University of Rome, Rome, Italy.
Institute for Immunological Research, University of Cartagena, Cartagena, Colombia.
Infect Genet Evol. 2021 Oct;94:104997. doi: 10.1016/j.meegid.2021.104997. Epub 2021 Jul 10.
The systematics and taxonomy of Ascaris lumbricoides and Ascaris suum, two of the world's most widespread nematodes, still represent a highly debated scientific issue. Two different transmission scenarios have been described according to endemicity: separated host-specific transmission cycles in endemic regions, and a single pool of infection shared by humans and pigs in non-endemic regions. The swine roundworm A. suum is now recognized as an important cause of human ascariasis also in endemic areas such as China, where cross-infections and hybridization have also been reported, as well as in non-endemic regions like Italy. This study aimed to investigate the molecular epidemiology of human and pig ascariasis in three countries representing different epidemiological scenarios: Italy as a non-endemic country, Colombia as an endemic country, and Slovakia as a non-endemic country, but with a poor socio-economic context linked to some focal populations of Roma settlements.
A total of 237 nematodes were analysed: 46 from Colombia (13 from humans, 33 from pigs), 114 from Slovakia (20 from humans, 94 from pigs) and 77 from Italy (17 from humans and 60 from pigs). Genotyping by PCR-RFLP of nuclear (ITS) and sequencing of mitochondrial (cox1) target regions were performed. ITS genotypes were used to estimate the Hardy-Weinberg (HW) equilibrium according to hosts and country of origin. The partial cox1 sequences were used to analyse genetic polymorphisms according to hosts and country of origin, as well as to infer the network of haplotypes, their evolutionary relationships and geographical distribution.
110 quality cox1 sequences were obtained. Haplotype network revealed three main groups corresponding to clade A, B and C. Clade C included most of the human cases from Italy, while those from Slovakia and Colombia were grouped in clade B. Ascaris from Italian and Colombian pigs showed HW equilibrium at the ITS marker, while disequilibrium was found in A. lumbricoides from Slovak pigs, which suggest a high unexpected amount of roundworms of human origin circulating also in pigs.
This study updates and extends the current understanding of Ascaris species and genotypes circulating in different epidemiological scenarios, with particular attention to the inclusion of human-derived Ascaris in the phylogenetic cluster C. Despite the evidence of HW equilibrium in the ITS in pig-derived Italian samples, the amount of genetic variation seems to support the existence of two closely related species.
作为世界上分布最广泛的两种线虫之一，蛔虫和猪蛔虫的系统分类和分类仍然是一个极具争议的科学问题。根据地方性，已经描述了两种不同的传播情况：地方性地区特定宿主的传播循环，以及非地方性地区人类和猪共用的单一感染池。猪蛔虫 A. suum 现在被认为是中国等地方性地区人类蛔虫病的一个重要原因，在这些地区也报告了交叉感染和杂交，以及在意大利等非地方性地区。本研究旨在调查代表不同流行病学情况的三个国家（意大利作为非地方性国家，哥伦比亚作为地方性国家，以及斯洛伐克作为非地方性国家，但与一些罗姆人定居点的焦点人群有关的贫困社会经济背景）的人类和猪蛔虫的分子流行病学。
共分析了 237 条线虫：46 条来自哥伦比亚（13 条来自人类，33 条来自猪），114 条来自斯洛伐克（20 条来自人类，94 条来自猪），77 条来自意大利（17 条来自人类，60 条来自猪）。通过聚合酶链反应-限制性片段长度多态性（PCR-RFLP）对核（ITS）和线粒体（cox1）靶区域进行基因分型，并对 ITS 基因型进行测序。根据宿主和原籍国，使用 ITS 基因型估计 Hardy-Weinberg（HW）平衡。部分 cox1 序列用于根据宿主和原籍国分析遗传多态性，以及推断单倍型网络、进化关系和地理分布。
获得了 110 条高质量的 cox1 序列。单倍型网络显示出三个主要的群组，对应于 clade A、B 和 C。clade C 包括来自意大利的大多数人类病例，而来自斯洛伐克和哥伦比亚的病例则被归为 clade B。意大利和哥伦比亚猪的蛔虫在 ITS 标记处显示出 HW 平衡，而斯洛伐克猪的蛔虫则显示出不平衡，这表明也有大量来自人类的蛔虫在猪中循环。
本研究更新并扩展了目前对不同流行病学情况下循环的蛔虫种和基因型的认识，特别关注包括人类来源的蛔虫在内的 clade C 进化枝。尽管在猪源性意大利样本中 ITS 处的 HW 平衡得到了证实，但遗传变异的数量似乎支持存在两种密切相关的物种。
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