Modelling the distributions of Culicoides bluetongue virus vectors in Sicily in relation to satellite‐derived climate variables

Abstract

Surveillance data from 268 sites in Sicily are used to develop climatic models for prediction of the distribution of the main European bluetongue virus (BTV) vector Culicoides imicola Kieffer (Diptera: Ceratopogonidae) and of potential novel vectors, Culicoides pulicaris Linnaeus, Culicoides obsoletus group Meigen and Culicoides newsteadi Austen. The models containing the 'best' climatic predictors of distribution for each species, were selected from combinations of 40 temporally Fourier-processed remotely sensed variables and altitude at a 1 km spatial resolution using discriminant analysis. Kappa values of around 0.6 for all species models indicated substantial levels of agreement between model predictions and observed data. Whilst the distributions of C. obsoletus group and C. newsteadi were predicted by temperature variables, those of C. pulicaris and C. imicola were determined mainly by normalized difference vegetation index (NDVI), a variable correlated with soil moisture and vegetation biomass and productivity. These models were used to predict species presence in unsampled pixels across Italy and for C. imicola across Europe and North Africa. The predicted continuous presence of C. pulicaris along the appenine mountains, from north to south Italy, suggests BTV transmission may be possible in a large proportion of this region and that seasonal transhumance (seasonal movement of livestock between upland and lowland pastures) even in C. imicola-free areas should not generally be considered safe. The predicted distribution of C. imicola distribution shows substantial agreement with observed surveillance data from Greece and Iberia (including the Balearics) and parts of mainland Italy (Lazio, Tuscany and areas of the Ionian coast) but is generally much more restricted than the observed distribution (in Sardinia, Corsica and Morocco). The low number of presence sites for C. imicola in Sicily meant that only a restricted range of potential C. imicola habitats were included in the training set and that predictions could only be made within this range. Future modelling exercises will use abundance data collected according to a standardized protocol across the Mediterranean and, for Sicily in particular, should include non-climatic environmental variables that may influence breeding site suitability such as soil type.

Abundance modelling of invasive and indigenous Culicoides species in Spain

“…Work by Wittmann et al (2001), Purse et al (2004) and Calvete et al (2008Calvete et al ( , 2009 confirms this relationship. In the case of the C. obsoletus group, the main factors were related to temperature (seven out of the 10 most important factors) and vegetation.…”

Comparison of single- and multi-scale models for the prediction of the Culicoides biting midge distribution in Germany

“…Since the availability of digital datasets of land cover, temperature, or potential hosts is continuously increasing, several studies have also used this kind of data to predict the prevalence of biting midge species, e.g. the normalised difference vegetation index (NDVI) (Purse et al, 2004;Calvete et al, 2008;Kluiters et al, 2013) or the CORINE land cover data (Kirkeby et al, 2009;Purse et al, 2011). These data are available or used on different scales raising the question, which spatial scale, or scales, should be chosen to reach the best possible predictions for different biting midge species.…”

“…Although there is huge lack of knowledge about the causal connection between environmental variables and the distribution of biting midges, several studies modelled biting midge distribution and phenology using different sets of environmental data (e.g. Purse et al, 2004Purse et al, , 2011Calvete et al, 2008;Kluiters et al, 2013). These modelling approaches used environmental data from various scales, e.g.…”

Bluetongue in Europe: vectors, epidemiology and climate change

“…In addition, BTV has previously been isolated from parous females (Mellor and Pitzolis 1979;Caracappa et al 2003), and the susceptibility to BTV of some C. obsoletus group populations in the UK is equal to or greater than that of C. imicola (Carpenter et al 2006). Finally, their predicted spatial distribution is capable of accounting for the distribution of those BTV outbreaks occurring outside the range of C. imicola (Purse et al 2004b(Purse et al , 2007. As a result, these species are also strongly implicated as the main vector in the current epizootic in northern Europe.…”