A Broad Assessment of Factors Determining Culicoides imicola Abundance: Modelling the Present and Forecasting Its Future in Climate Change Scenarios

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.

Mosquitoes and Culicoides biting midges: vector range and the influence of climate change

“…Indeed, in Italy at least, C. imicola would appear to be in stasis as it has shown no expansion whatsoever in its range since the year 2000, when Italy implemented its large-scale vector surveillance programme, which has been maintained continuously ever since (69). This suggests that, at some point after the last Ice Age, the distribution of C. imicola stabilised within the Mediterranean Basin, but remains fragmented and A recent modelling study (70) indirectly supported the view that C. imicola is constrained by its ecology and indicated that there is no evidence to suggest that its range in Spain will expand; nevertheless, it is expected that C. imicola will become more abundant in the future, in particular in those south-western areas where it has long been established and where, in all likelihood, it was involved in the large outbreaks of bluetongue that affected the region in the 1950s. A subsequent micro-satellite study (71), conducted on more than 20 populations of C. imicola collected from around the southern and northern shores of the Mediterranean Sea, points unequivocally to its ancient presence within the Basin and suggests that there is longitudinal and ongoing gene flow between the North African and Central Mediterranean populations.…”

Modelling the Spatial Distribution of Culicoides imicola: Climatic versus Remote Sensing Data

“…This dependency on air temperature was confirmed in several C. imicola modelling studies using climatic data. Purse et al [18] found C. imicola in the Mediterranean Basin to occur in warm (annual mean [12][13][14][15][16][17][18][19][20] • C) regions with low seasonal variations. A model developed by…”

“…Conte et al [11] added the presence of water in rivers to meteorological and topographic data for a model for Italy based on 546 trapping sites, resulting in 75% correctly classified sites in an internal validation. Acevedo et al [12] included the availability of host species, as well as land cover, climatic and pedological variables, in an analysis based on trappings during the period [2005][2006][2007][2008] in Spain.…”

Favorabilidad ecogeográfica para el corzo: distribución y abundancia

“…Así, la estimación de la abundancia de una especie en todo su área de distribución es un proceso clave para poder comprender el ciclo epidemiológico de los patóge-nos en los que dicha especie juega un papel relevante bien como vector u hospedador. Por ejemplo, la abundancia de ciervo (Cervus elaphus), estimada mediante SDM, ha sido recientemente utilizada para estudiar el papel que ésta juega en la abundancia del principal vector del virus de la lengua azul (Culicoides imicola) en la Península Ibérica (Acevedo et al, 2010c). Desde el punto de vista de la sanidad animal es necesario también conocer la abundancia de las poblaciones para poder establecer planes de contingencia frente a la entrada de un patógeno en el territorio como los que actualmente están emergiendo en la Península Ibérica (Ruiz-Fons et al, 2008).…”