Abstract
Bluetongue (BT) is still present in Europe and the introduction of new serotypes from endemic areas in the African continent is a possible threat. Culicoides imicola remains one of the most relevant BT vectors in Spain and research on the environmental determinants driving its life cycle is key to preventing and controlling BT. Our aim was to improve our understanding of the biotic and abiotic determinants of C. imicola by modelling its present abundance, studying the spatial pattern of predicted abundance in relation to BT outbreaks, and investigating how the predicted current distribution and abundance patterns might change under future (2011–2040) scenarios of climate change according to the Intergovernmental Panel on Climate Change. C. imicola abundance data from the bluetongue national surveillance programme were modelled with spatial, topoclimatic, host and soil factors. The influence of these factors was further assessed by variation partitioning procedures. The predicted abundance of C. imicola was also projected to a future period. Variation partitioning demonstrated that the pure effect of host and topoclimate factors explained a high percentage (>80%) of the variation. The pure effect of soil followed in importance in explaining the abundance of C. imicola. A close link was confirmed between C. imicola abundance and BT outbreaks. To the best of our knowledge, this study is the first to consider wild and domestic hosts in predictive modelling for an arthropod vector. The main findings regarding the near future show that there is no evidence to suggest that there will be an important increase in the distribution range of C. imicola; this contrasts with an expected increase in abundance in the areas where it is already present in mainland Spain. What may be expected regarding the future scenario for orbiviruses in mainland Spain, is that higher predicted C. imicola abundance may significantly change the rate of transmission of orbiviruses.
Highlights
Understanding the patterns and mechanisms of species occurrence and abundance is a central issue in ecology and epidemiology
The increased application of spatial models to conservation biology and wildlife management has been driven, at least in part, by the advent of extensive computerised spatial databases — for example the Worldclim project — and powerful analytical tools [2]. This discipline has rarely focused on pathogen ecology, i.e. epidemiology [4], as was demonstrated at the 4th meeting of the International Biogeography Society in 2009, where a symposium was designed to introduce to biogeographers the many ways that this discipline can contribute to the study of disease ecology [5]
Variation partitioning demonstrated that the pure effect of host and topoclimate factors explained a high percent (.80%) of the variation
Summary
Understanding the patterns and mechanisms of species occurrence and abundance is a central issue in ecology and epidemiology. The increased application of spatial models to conservation biology and wildlife management has been driven, at least in part, by the advent of extensive computerised spatial databases — for example the Worldclim project (www.worldclim.org) — and powerful analytical tools [2]. This discipline has rarely focused on pathogen ecology (but see [3]), i.e. epidemiology [4], as was demonstrated at the 4th meeting of the International Biogeography Society in 2009, where a symposium was designed to introduce to biogeographers the many ways that this discipline can contribute to the study of disease ecology [5]. Biotic factors in these systems are the main determinants of pathogen distribution, and abiotic factors may indirectly affect their distribution by interfering with host and vector distribution and abundance [8]
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