Towards Understanding the Impacts of Environmental Variation on Echinococcus multilocularis Transmission.
Résumé
The cestode Echinococcus multilocularis is transmitted from small mammal intermediate hosts (IH) to canid definitive hosts via the predator-prey relationship. Transmission intensity is controlled by host intrinsic factors (e.g. immunity) and behaviour, by climatic factors, and by complex host interactions (e.g. predator-prey relationship). Mechanistic models have been developed to predict parasite abundance and prevalence in wildlife. They generally rely on oversimplistic assumptions due to key parameters that can hardly be estimated reliably from field studies. Those assumptions become critical when attempting to describe transmission dynamics in regions where host population densities vary in space and time and over larger areas, potentially including several biogeographical areas which may be interconnected and a number of ecological conditions and host assemblages. This is the case in Western China where complexity in transmission systems arises from factors interacting at various spatial scales: (i) on a continental range the general composition of host communities are driven by bio-geographical influences; (ii) on a regional range the small mammal populations dynamics and community structures are responsive to anthropogenic landscape modifications (e.g. deforestation/afforestation, grazing pressure on grasslands). It is expected that further advances will come from methods combining multi-level field approaches with modern regression techniques coupled with traditional transmission models.