Genetic variation of Echinococcus spp. in yaks and sheep in the Tibet Autonomous Region of China based on mitochondrial DNA

Abstract

BackgroundCystic echinococcosis (CE) in humans and livestock is caused by Echinococcus granulosus (sensu lato). In China where CE is endemic, a number of studies have shown that Echinococcus granulosus (sensu stricto) is majorly responsible for CE. However, E. canadensis (G6) which is the second leading cause of CE is now being detected in most parts of the country. In this study, the species diversity and genetic variation of Echinococcus granulosus (s.l.) in four counties in Tibet Autonomous Region of China were investigated.MethodsInfection with Echinococcus granulosus (s.s.) in yaks and sheep was identified using NADH dehydrogenase subunit 1 and 5 (nad1 and nad5) mitochondrial genes while the genotype G6 of E. canadensis initially diagnosed with NADH dehydrogenase subunit 1 (nad1) was further confirmed by analysis of the complete mitochondrial genome and a phylogenetic network constructed based on the nad2 and nad5 genes.ResultsOut of 85 hydatid cyst samples collected from slaughtered sheep (n = 54) and yaks (n = 31), 83 were identified as E. granulosus (s.s.) G1 (n = 77), G3 (n = 6) and 2 were identified as E. canadensis G6. Analysis of the nad1/nad5 genes revealed 16/17 mutations with 9/14 parsimony informative sites resulting in 15/14 haplotypes, respectively. Haplotype diversity (Hd) and nucleotide diversity (π) of E. granulosus (s.s.) population were 0.650 and 0.00127 for nad1 and 0.782 and 0.00306 for nad5, respectively, with an overall negative Tajima’s D and Fu’s Fs. A low FST indicated no genetic difference between isolates from sheep and yaks.ConclusionPockets of infection with E. canadensis (G6, G7, G8 and G10) have been previously reported in sheep, goats, yaks and/or humans in different parts of China. While the G6 genotype has been previously reported in sheep in the Tibet Autonomous Region, the detection in a yak in the present study represents the first to the best of our knowledge. Therefore, we recommend future surveys and control efforts to comprehensively investigate other potential intermediate hosts for the prevalence and genetic diversity of the E. canadensis group (G6, G7, G8 and G10) across the country and their inclusion into the existing CE control programme.

Echinococcus spp. and genotypes infecting humans in Tibet Autonomous Region of China: a molecular investigation with near-complete/complete mitochondrial sequences

“…Although the prevalence of echinococcosis was explored [ 28 ], the causative agents of human infection have not yet been fully understood in TAR. Previous molecular studies on the Tibetan Plateau often included samples from animals; even when samples from humans were involved, they were mainly patients from Qinghai or Sichuan Provinces, with few patients from TAR; moreover, previous studies were using short fragments of the mtDNA with limited phylogenetic resolution [ 5 , 9 , 25 – 27 ].…”

“…Although there was a prevalence study in TAR using ultrasound diagnostics, molecular markers were seldom used to identify the Echinococcus species and genotypes infecting the echinococcosis patients in TAR. Previous molecular epidemiological studies in this region often included animal samples with very few samples from humans; even when samples from patients were involved, they were mainly patients from Qinghai or Sichuan Provinces, but rarely patients from TAR; besides, previous studies were using short fragments of the mtDNA such as cox 1, a fragment of cox 1, nad 1, and atp 6 [ 5 , 9 , 25 – 27 ], which could not confidently allocate the samples into specific genotypes and could only generate networks with lower resolution; therefore, the exact Echinococcus species and genotypes infecting humans in TAR remain unknown. The accurate allocation of the samples into different species and genotypes is the prerequisite for the exploration of the epidemiology, pathology, and infectivity to humans of the different species and genotypes.…”

Echinococcus shiquicus in Qinghai–Tibet plateau: population structure and confirmation of additional endemic areas

“…Compared to other species of Echinococcus present on the Tibetan Plateau, for example, E. multilocularis, a sister species to E. shiquicus which also shares similar host characteristics, demonstrates a relatively lower mitochondrial polymorphism (Nakao et al, 2010;Li et al, 2018), although this species has a more generalistic host requirement with zoonotic potentials. Similarly, on the plateau low mitochondrial polymorphism is also true for E. granulosus sensu stricto, a widespread and geographically expanding species (Nakao et al, 2010;Ohiolei et al, 2019).…”

Haplotyping of Echinococcus granulosus Isolates From Human, Sheep and Cattles Hydatid Cysts in Some Central Euphrates Provinces, Iraq

“…Whereas the relationship between human and cattle represented with identical haplotype (H11) , that means the most infection of human with hydatid cysts come from dogs that ate hydatid cysts from cattle. Through the study it was found that the two isolates number (1,8) these isolate genetically similar to isolates from sheep in the city (Saga in Japan), isolates number (2,3,4,5,6) genetically similar to isolates from sheep and yak in the city (Zhongba in China) (16) . The isolates number(7) genetically similar to isolates from human in the China country (17) .…”