Talk, INTERNATIONAL CONFERENCE EDEN 2010 - Emerging Vector-borne Diseases in a Changing European Environment, Montpellier: 2010-05-10 - 2010-05-12
Phlebotomus species, which are native to Southern Europe, are important vectors for sandfly-borne diseases (e.g. leishmaniasis). Several species are recorded, but the density of records is rather low in many regions. These cold-blooded insects cannot regulate their body temperature themselves. Activity phase and survival are strongly connected with the local environmental conditions. As a consequence of climatic changes, the northward spread of these vectors is expected. This is supported by recent sandfly catches and autochthonous cases of leishmaniasis in humans and their domestic animals in Central Europe, e.g. in Germany. Nevertheless, until now most infections of leishmaniasis at higher latitudes are reported from overseas travellers or dogs imported from the Mediterranean Region, the preferred holiday destination of Europeans. In this investigation we highlight the restrictions and options for the projection of habitat shift for various Phlebotomus species. Bioclimate envelopes are modelled for species which prefer maritime climatic conditions without strong changes in temperature - P.ariasi, P. perniciosus, P. mascittii (assumed but unproven vector competence) - as well as for species with a south-eastern focus of distribution (P. neglectus, P. perfiliewi, P. tobbi). Uncertainties in projections of the influence of climatic variables are fundamentally dependent on the realization of emission scenarios for greenhouse gases. Then, scale-dependent differences in mechanistic projections between global or regional climate models have to be considered. In addition to thermal factors, the precipitation regime is a source of uncertainty as it is highly variable already by nature. Here, the future projections differ strongly as well in time as in space. Furthermore, it is difficult to estimate the magnitude and frequency of increasing extreme climatic events, which may be decisive for the establishment and disappearance of vectors, respectively. Anyhow, even if future suitable climatic habitats for Phlebotomus species are detected - more or less accurate, depending on model quality - they should not be taken to provide certain forecasts. Whether sandflies can follow their spatially and temporally moving potential climatic or environmental niche is regulated by many other factors, including dispersal ability and barriers. The Alps still can be seen as a natural barrier, which prevents a direct and short-track spread from northern Italy to Central Europe, even if climatic conditions on the northern side are suitable or will become suitable. Furthermore, uncertainties are related to the limited knowledge of sandfly ecology and, beyond that, on the role of potential evolutionary effects that can not be ignored in such short-lived species. Despite all uncertainties about future tendencies in a rapidly changing environment, one fact is quite clear. Phlebotomine sandflies will occur close to humans and their domestic animals, which provide the preferred blood-meal for the females.