Abstract
From continental to regional scales, the zoonosis alveolar echinococcosis (AE) (caused by Echinococcus multilocularis) forms discrete patches of endemicity within which transmission hotspots of much larger prevalence may occur. Since the late 80s, a number of hotspots have been identified in continental Asia, mostly in China, wherein the ecology of intermediate host communities has been described. This is the case in south Gansu, at the eastern border of the Tibetan plateau, in south Ningxia, in the western Tian Shan of Xinjiang, and in the Alay valley of south Kyrgyzstan. Here we present a comparative natural history and characteristics of transmission ecosystems or ecoscapes. On this basis, regional types of transmission and their ecological characteristics have been proposed in a general framework. Combining climatic, land cover and intermediate host species distribution data, we identified and mapped 4 spatially distinct types of transmission ecosystems typified by the presence of one of the following small mammal 'flagship' species: Ellobius tancrei, Ochotona curzoniae, Lasiopodomys brandtii or Eospalax fontanierii. Each transmission ecosystem had its own characteristics which can serve as a reference for further in-depth research in the transmission ecology of E. multilocularis. This approach may be used at fine spatial scales to characterize other poorly known transmission systems of the large Eurasian endemic zone, and help in consideration of surveillance systems and interventions.
Highlights
Grassland small mammal communities are characterized by the presence of O. curzoniae, selected here as the flagship species, because being diurnal it is detected and easy to identify, directly or based on its indices
On the Tibetan plateau or elsewhere for that matter, evidence of a dog population infected with no link to a sylvatic cycle is lacking, which poses the question of transmission sustainability in an isolated population of dogs
A striking feature of the transmission ecology of E. multilocularis in China and in some neighbouring countries of Central Asia is the diversity of potential small mammal intermediate hosts and the range of ecological and anthropogenic drivers that directly or indirectly contribute to reinforce or limit the parasite lifecycle in sylvatic mammals
Summary
In the past three decades, Echinococcus multilocularis, the causative agent of human alveolar echinococcosis (AE), has been newly reported in countries of Europe (Davidson et al 2012) and discovered in foci of relatively high incidence in China and neighbouring countries of Central Asia and Siberia (Craig et al 1992; Ito et al 2003, 2010; Li et al 2005; Yang et al 2006; Torgerson et al 2009; Ziadinov et al 2011; Konyaev et al 2012). The amplitude of seasonal and inter-annual variations of population densities of some arvicolid and/or lagomorph small mammal species increases with the ratio of their optimal habitat to the total available habitat (Lidicker, 2000) This may lead to phases of large population densities where the biomass of the total population of intermediate host can reach several tens of kilograms per ha. During those periods, fox definitive hosts feed almost exclusively on those prey populations that are easy to access and are more likely to ingest infected small mammals even when prevalence is low (Raoul et al 2010). Even in areas where an overall higher prevalence of human AE was observed and the combination of apparent favourable climate and landscape was met, there still remained large unexplained differences between sampling units (generally villages) (Danson et al 2003, 2004)
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