Abstract
The Qinghai-Tibet Plateau is a highly endemic area of alveolar echinococcosis where a series of intermediate hosts, especially voles and pikas, are infected with Echinococcus multilocularis. The metacestodes of E. multilocularis are fluid-filled, asexually proliferating cysts, and they are mainly found in the host's liver in the form of tumor-like growths. In this study, we investigated the genetic variations of E. multilocularis in four mitochondrial (mt) genes, namely, NADH dehydrogenase subunit 5 (nad5), adenosine triphosphate subunit 6 (atp6), cytochrome c oxidase subunit 1 (cox1), and NADH dehydrogenase subunit 1 (nad1). The complete nad5, atp6, cox1, and nad1 genes were amplified separately from each hydatid cyst isolate using polymerase chain reaction (PCR) and then sequenced. Phylogenetic trees were then generated based on the combined mt genes using MrBayes 3.1.2 and PAUP version 4.0b10. The results showed that thirty of 102 voles and two of 49 pikas were infected with E. multilocularis. The genetic variation distances among all E. multilocularis samples were 0.1–0.4%, 0.2–0.4%, 0.1–0.6%, and 0.1–0.4% for nad5, atp6, nad1, and cox1, respectively. Compared to previous studies of the genetic diversity of E. multilocularis based on the cox1 gene, the genetic distances within the same group were 1.3–1.7% (Mongolia strain), 0.6–0.8% (North American strain), 0.3–0.6% (European strain), and 0.1–0.4% (Asian strain). Based on concatenated sequences of the nad5, atp6, cox1, and nad1 genes all haplotypes were divided into two clusters. In conclusion, the genetic diversity of E. multilocularis based on mt genes on a small local area is at low level but between different regions with long distance and different ecological environment each other, the genetic diversity is at relatively high level; genetic variation is higher in the nad1 gene than that in the other three mt genes. The results on a local scale provide basic information for further study of the molecular epidemiology, genetic differences and control of E. multilocularis in Qinghai Province, China.
Highlights
Echinococcus multilocularis is a small cestode that cause the parasitic zoonosis alveolar echinococcosis (AE), which was one of the 17 neglected tropical diseases (NTDs) prioritized by the World Health Organization (WHO) in 2012 (Agudelo Higuita et al, 2016)
All animals were handled in strict accordance with good animal practice according to the Animal Ethics Procedures and Guidelines of the People’s Republic of China, and the study was approved by the Animal Ethics Committee of Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences (No LVRIAEC2012-007)
The sequence analysis with the reference sequence in this study further predicted that all of the samples or specimens isolated from plateau voles and pikas belonged to E. multilocularis
Summary
Echinococcus multilocularis is a small cestode that cause the parasitic zoonosis alveolar echinococcosis (AE), which was one of the 17 neglected tropical diseases (NTDs) prioritized by the World Health Organization (WHO) in 2012 (Agudelo Higuita et al, 2016). E. multilocularis is mainly distributed in holarctic regions, including North America ( found in southwestern Ontario), Europe, and Asia (Massolo et al, 2014; Oksanen et al, 2016; Deplazes et al, 2017; Trotz-Williams et al, 2017). E. multilocularis infects two kinds of hosts: the typical intermediate host (IH), a wide spectrum of mammalian species including small herbivorous, rodents (predominantly) and pikas, and the typical definitive hosts (DH), which are canids and mammalian species, including foxes, wolves, dogs, and cats (Vuitton et al, 2003; Deplazes et al, 2011; Hegglin and Deplazes, 2013; Conraths and Deplazes, 2015; Raoul et al, 2015; Knapp et al, 2016; Eckert and Thompson, 2017). The parasite larvae travel to internal organs, mainly the liver (Torgerson et al, 2010; Conraths et al, 2017)
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