Echinococcus multilocularis and Echinococcus shiquicus in a small mammal community on the eastern Tibetan Plateau: host species composition, molecular prevalence, and epidemiological implications - PubMed (original) (raw)

doi: 10.1186/s13071-018-2873-x.

Jiayu Liu 1, Qingqiu Zuo 1, Zhiqiang Mu 1, Xiaodong Weng 1, Xiaohui Sun 1, Junyao Wang 1, Belgees Boufana 2, Philip S Craig 3, Patrick Giraudoux 4, Francis Raoul 4, Zhenghuan Wang 5

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Echinococcus multilocularis and Echinococcus shiquicus in a small mammal community on the eastern Tibetan Plateau: host species composition, molecular prevalence, and epidemiological implications

Xu Wang et al. Parasit Vectors. 2018.

Abstract

Background: The eastern part of the Tibetan Plateau is now recognized as an endemic region with the highest reported human infection rates in the world of human alveolar echinococcosis (AE) caused by Echinococcus multilocularis. Existing epidemiological studies on AE have mainly focused on the synanthropic environment, while basic parasitological and ecological aspects in wildlife host species remain largely unknown, especially for small mammal hosts. Therefore, we examined small mammal host species composition, occurrence, and the prevalence of both E. multilocularis and E. shiquicus in Shiqu County (Sichuan Province, China), eastern Tibetan Plateau.

Results: In total, 346 small mammals from five rodent and one pika species were trapped from four randomly set 0.25 ha square plots. Two vole species, Lasiopodomys fuscus (n = 144) and Microtus limnophilus (n = 44), and the plateau pika (Ochotona curzoniae) (n = 135), were the three most-dominant species trapped. Although protoscoleces of E. multilocularis and E. shiquicus were only observed in L. fuscus and O. curzoniae, respectively, cox1 and nad1 gene DNA of E. shiquicus was detected in all the small mammal species except for Neodon irene, whereas E. multilocularis was detected in the three most-dominant species. The overall molecular prevalence of Echinococcus species was 5.8 (95% CI: 3.3-8.2%) ~ 10.7% (95% CI: 7.4-14.0%) (the conservative prevalence to the maximum prevalence with 95% CI in parentheses), whereas for E. multilocularis it was 4.3 (95% CI: 2.2-6.5%) ~ 6.7% (95% CI: 4.0-9.3%), and 1.5 (95% CI: 0.2-2.7%) ~ 4.1% (95% CI: 2.0-6.1%) for E. shiquicus. The prevalence of both E. multilocularis and E. shiquicus, was significantly higher in rodents (mainly voles) than in pikas. Phylogenetic analyses revealed that Echinococcus haplotypes of cox1 from small mammal hosts were actively involved in the sylvatic and anthropogenic transmission cycles of E. multilocularis in the eastern Tibetan Plateau.

Conclusions: In contrast to previous studies, the current results indicated that rodent species, rather than pikas, are probably more important natural intermediate hosts of E. multilocularis and E. shiquicus in the eastern Tibetan Plateau. Thus, understanding interspecific dynamics between rodents and pikas is essential to studies of the echinococcosis transmission mechanism and human echinococcosis prevention in local communities.

Keywords: E. shiquicus; Echinococcus multilocularis; Prevalence; Small mammal; Tibetan Plateau.

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Conflict of interest statement

The protocol used to collect the small mammals was approved by the East China Normal University Animal Care and Use Committee (identification number: Q20170501).

Competing interests

The authors declare that they have no competing interests

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Figures

Fig. 1

Fig. 1

Network of 33 _Echinococcus multilocularis cox_1 gene haplotypes collected from samples in this study. The size of the circle represents the number of species of hosts with the E. multilocularis gene haplotype (Hap06 isolated from six species including humans, dogs, Tibetan foxes, two species of voles and plateau pikas, while each of the other haplotypes has only one host species, see Additional file 1: Table S1 for details). The distance between the circle centers shows the variation between two haplotypes (i.e. 1 bp mutation between Hap06 and Hap36)

Fig. 2

Fig. 2

Phylogenetic tree comparing the geographical distribution between mtDNA _cox_1 gene haplotypes of Echinococcus multilocularis. The Bayesian phylogenetic analysis was used by setting the “TIM3+I” substitution model, 2,000,000-generation MCMC posterior probability estimation with a 1000-generation sampling interval, and discarding the first 25% samples when summing up trees

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