Biological Sciences Department, Faculty of Science, University of Calgary, Calgary, Alberta, Canada.
Department of Comparative Biology and Experimental Medicine, Host Parasite Interactions (HPI) program, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada.
PLoS Negl Trop Dis. 2021 May 26;15(5):e0009428. doi: 10.1371/journal.pntd.0009428. eCollection 2021 May.
Echinococcus multilocularis (Em) is a zoonotic parasite considered a global emergent pathogen. Recent findings indicate that the parasite is expanding its range in North America and that European-type haplotypes are circulating in western Canada. However, genetic analyses are usually conducted only on a few parasites out of thousands of individuals within each definitive host, likely underestimating the prevalence of less common haplotypes. Moreover, mixed infections with several mtDNA haplotypes in the same host have been reported, but their relative abundance within the host was never estimated. We aimed to 1) estimate the frequency of co-infections of different Em haplotypes in coyotes (Canis latrans) and red foxes (Vulpes vulpes) from western Canada and their relative abundance within the definitive hosts, 2) detect less prevalent haplotypes by sampling a larger proportion of the parasite subpopulation per host, and 3) investigate differences in the distribution of Em haplotypes in these main definitive hosts; foxes and coyotes. We extracted DNA from ~10% of the worm subpopulation per host (20 foxes and 47 coyotes) and used deep amplicon sequencing (NGS technology) on four loci, targeting the most polymorphic regions from the mitochondrial genes cox1 (814 bp), nad1 (344 bp), and cob (387 bp). We detected the presence of mixed infections with multiple Em haplotypes and with different Echinococcus species including Em and E. granulosus s.l. genotypes G8/G10, low intraspecific diversity of Em, and a higher abundance of the European-type haplotypes in both hosts. Our results suggest a population expansion of the European over the North American strain in Alberta and a limited distribution of some European-type haplotypes. Our findings indicate that deep amplicon sequencing represents a valuable tool to characterize Em in multiple hosts, to assess the current distribution and possible origins of the European strain in North America. The potential use of next-generation sequencing technologies is particularly important to understand the patterns of geographic expansion of this parasite.
多房棘球绦虫（Em）是一种被认为具有全球新兴病原体特征的动物源性寄生虫。最近的研究结果表明，该寄生虫在北美的分布范围正在扩大，并且欧洲型单倍型正在加拿大西部流行。然而，通常仅对每个终宿主的数千个个体中的少数寄生虫进行遗传分析，这可能低估了不太常见单倍型的流行率。此外，已经报道了同一宿主中几种 mtDNA 单倍型的混合感染，但从未估计过它们在宿主中的相对丰度。我们的目的是：1）估计来自加拿大西部的土狼（Canis latrans）和红狐（Vulpes vulpes）中不同 Em 单倍型的混合感染频率及其在终宿主中的相对丰度；2）通过对每个宿主的寄生虫亚群进行更大比例的抽样来检测较少流行的单倍型；3）研究这些主要终宿主（狐狸和土狼）中 Em 单倍型的分布差异。我们从每个宿主的虫体亚群中提取了约 10%的 DNA（20 只狐狸和 47 只土狼），并使用深度扩增子测序（NGS 技术）对线粒体基因 cox1（814 bp）、nad1（344 bp）和 cob（387 bp）的最多态性区域进行了四个基因座的靶向检测。我们检测到存在多种 Em 单倍型的混合感染以及包括 Em 和 E. granulosus s.l.基因型 G8/G10 在内的不同的棘球属物种的感染，Em 的种内多样性较低，并且在两种宿主中欧洲型单倍型的丰度较高。我们的结果表明，在艾伯塔省，欧洲型相对于北美型的种群正在扩张，并且一些欧洲型单倍型的分布有限。我们的研究结果表明，深度扩增子测序是一种在多个宿主中描述 Em 的有效工具，可用于评估当前北美欧洲型菌株的分布情况和可能来源。下一代测序技术的潜在应用对于了解该寄生虫的地理扩张模式尤为重要。
