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

Wang, X; Liu, J; Zuo, Q; Mu, Z; Weng, X; Sun, X; Wang, J; Boufana, B; Craig, PS; Giraudoux, P; Raoul, F; Wang, Z

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:
Echinococcus multilocularis, E. shiquicus, Small mammal Prevalence, Tibetan Plateau

• Journal Article Type: Article
• Acceptance Date: Apr 25, 2018
• Online Publication Date: May 16, 2018
• Publication Date: May 16, 2018
• Deposit Date: May 29, 2018
• Publicly Available Date: May 29, 2018
• Journal: Parasites & Vectors
• Electronic ISSN: 1756-3305
• Publisher: Springer Verlag
• Volume: 11
• Issue: 1
• Pages: 302
• DOI: https://doi.org/10.1186/s13071-018-2873-x
• Keywords: E. shiquicus, Echinococcus multilocularis, Prevalence, Small mammal, Tibetan Plateau
• Publisher URL: https://doi.org/10.1186/s13071-018-2873-x
• Additional Information: Funders : National Natural Science Foundation of China;Ministry Science and Technology of China;National Science Foundation;Wellcome Trust;FIC NIH HHS; Projects : 31470488;2016YFC0503200;31071944;#TW001565;#094325/Z/10/Z;R01 TW001565