Culicoides biting midges (Diptera: Ceratopogonidae) are the main vectors of livestock diseases such as bluetongue (BT) which mainly affect sheep and cattle. In Spain, bluetongue virus (BTV) is transmitted by several Culicoides taxa, including Culicoides imicola, Obsoletus complex, Culicoides newsteadi and Culicoides pulicaris that vary in seasonality and distribution, affecting the distribution and dynamics of BT outbreaks. Path analysis is useful for separating direct and indirect, biotic and abiotic determinants of species' population performance and is ideal for understanding the sensitivity of adult Culicoides dynamics to multiple environmental drivers. Start, end of season and length of overwintering of adult Culicoides were analysed across 329 sites in Spain sampled from 2005 to 2010 during the National Entomosurveillance Program for BTV with path analysis, to determine the direct and indirect effects of land use, climate and host factor variables. Culicoides taxa had species-specific responses to environmental variables. While the seasonality of adult C. imicola was strongly affected by topography, temperature, cover of agro-forestry and sclerophyllous vegetation, rainfall, livestock density, photoperiod in autumn and the abundance of Culicoides females, Obsoletus complex species seasonality was affected by land-use variables such as cover of natural grassland and broad-leaved forest. Culicoides female abundance was the most explanatory variable for the seasonality of C. newsteadi, while C. pulicaris showed that temperature during winter and the photoperiod in November had a strong effect on the start of the season and the length of overwinter period of this species. These results indicate that the seasonal vector-free period (SVFP) in Spain will vary between competent vector taxa and geographic locations, dependent on the different responses of each taxa to environmental conditions.

Bluetongue is a disease of major economic concern in Europe. Its causative agent, bluetongue virus (BTV), is transmitted by several Culicoides species (mainly Culicoides imicola and Culicoides obsoletus in Europe). The application of insecticides on animals may reduce transmission of BTV, however, no formulation is currently licensed specifically against Culicoides midges. The present study assesses the susceptibility of C. obsoletus to deltamethrin using an adapted World Health Organization (WHO) susceptibility test. Midges were exposed to different dosages of deltamethrin for 1 h, and mortality after 1 h and 24 h was recorded. Results indicated that deltamethrin is highly toxic to C. obsoletus since a dose of 1·33×10−4% was enough to kill 50% of the population (LD50) in 24 h. The deltamethrin concentration needed to kill 90% of the population (LD90) was 5·55×10−4%. The results obtained in the present work could help to create a system that can be used to assess insecticide resistance and susceptibility of Culicoides biting midges.

Existing algorithms for predicting species' distributions sit on a continuum between purely statistical and purely biological approaches. Most of the existing algorithms are aspatial because they do not consider the spatial context, the occurrence of the species or conditions conducive to the species' existence, in neighbouring areas. The geostatistical techniques of kriging and cokriging are presented in an attempt to encourage biologists more frequently to consider them. Unlike deterministic spatial techniques they provide estimates of prediction errors. The assumptions and applications of common geostatistical techniques are presented with worked examples drawn from a dataset of the bluetongue outbreak in northwest Europe in 2006. Emphasis is placed on the importance and interpretation of weights in geostatistical calculations. Covarying environmental data may be used to improve predictions of species’ distributions, but only if their sampling frequency is greater than that of the species’ or disease data. Cokriging techniques are unable to determine the biological significance or importance of such environmental data, because they are not designed to do so.

Bluetongue (BT) is a disease of ruminants caused by bluetongue virus (BTV), which is spread between its hosts by Culicoides midges. Vaccination is the most effective way to protect susceptible animals against BTV and was used reactively to control the recent northern European outbreak. To assess the consequences of using vaccination pre-emptively we used a stochastic, spatially explicit model to compare reactive and pre-emptive vaccination strategies against an incursion of BTV serotype 1 (BTV-1) into Great Britain. Both pre-emptive and reactive vaccination significantly reduced the number of affected farms and limited host morbidity and mortality. In addition, vaccinating prior to the introduction of disease reduced the probability of an outbreak occurring. Of the strategies simulated, widespread reactive vaccination resulted in the lowest levels of morbidity. The predicted effects of vaccination were found to be sensitive to vaccine efficacy but not to the choice of transmission kernel.

Culicoides imicola is the main vector for bluetongue (BT) and African horse sickness (AHS) viruses in the Mediterranean basin and in southern Europe. In this study, we analysed partial mitochondrial cytochrome c oxidase subunit I (COI) gene to characterize and confirm population expansion of Culicoides imicola across Spain. The data were analysed at two hierarchical levels to test the relationship between C. imicola haplotypes in Spain (n=215 from 58 different locations) and worldwide (n=277). We found nineteen different haplotypes within the Spanish population, including 11 new haplotypes. No matrilineal subdivision was found within the Spanish population, while western and eastern Mediterranean C. imicola populations were very structured. These findings were further supported by median networks and mismatch haplotype distributions. Median networks demonstrated that the haplotypes we observed in the western Mediterranean region were closely related with one another, creating a clear star-like phylogeny separated only by a single mutation from eastern haplotypes. The two, genetically distinct, sources of C. imicola in the Mediterranean basin, thus, were confirmed. This type of star-like population structure centred around the most frequent haplotype is best explained by rapid expansion. Furthermore, the proposed northern expansion was also supported by the statistically negative Tajima's D and Fu's Fs values, as well as predicted mismatch distributions of sudden and spatially expanding populations. Our results thus indicated that C. imicola population expansion was a rapid and recent phenomenon.

In a bluetongue (BT) disease project, light trappings of Culicoides were conducted in 19 localities and 39,000 biting midges were examined. BT virus type 16 was isolated in 1968 at Devora from a pool consisting mainly of Culicoides schultzei gp and C. imicola; BT virus type 4 was isolated in 1969 at Yesodot from a pool of 183 C. imicola; BT virus type 2 was isolated in 1979 at Talmé El'azar from pools consisting of 2462 C. imicola; and BT virus type 6 was isolated 3 times in 1980 at Bet Dagan from pools of 204, 258 and from 143 C. imicola, respectively. In the Akabane project (1976 and 1977) 4632 Culicoides and 1867 mosquitoes from four localities were trapped and examined. An arbovirus which was not Akabane, BT or turkey meningo-encephalitis (TME) was isolated from a pool of 44 engorged Culex pipiens complex trapped in Gan Shemuel. In the Rift Valley fever project, which was conducted in 1978 and 1979 due to the presence of an epidemic in Egypt, 351 mosquitoes of four species and 7098 Culicoides of 14 species were tested and none were found to harbour an arbovirus. Within the TME project more than 12,000 Culicoides and 9000 mosquitoes from 14 localities were tested. Positive isolations of TME were made from an unsorted pool of mosquitoes from Gesher haziw, an unsorted pool of 13 Culicoides from Nahalal, a pool of 223 unidentified Culicoides from Zetan and a pool of 12 engorged Cx pipiens complex from the same locality. Other pathogens which were not identified to species level were also isolated.