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BackgroundReunion Island regularly faces outbreaks of epizootic haemorrhagic disease (EHD) and bluetongue (BT), two viral diseases transmitted by haematophagous midges of the genusCulicoides(Diptera: Ceratopogonidae) to ruminants. To date, five species ofCulicoidesare recorded in Reunion Island in which the first two are proven vector species:Culicoides bolitinos,C. imicola,C. enderleini,C. grahamiiandC. kibatiensis. Meteorological and environmental factors can severely constrainCulicoidespopulations and activities and thereby affect dispersion and intensity of transmission ofCulicoides-borne viruses. The aim of this study was to describe and predict the temporal dynamics of allCulicoidesspecies present in Reunion Island.MethodsBetween 2016 and 2018, 55 biweeklyCulicoidescatches using Onderstepoort Veterinary Institute traps were set up in 11 sites. A hurdle model (i.e. a presence/absence model combined with an abundance model) was developed for each species in order to determine meteorological and environmental drivers of presence and abundance ofCulicoides.ResultsAbundance displayed very strong heterogeneity between sites. AverageCulicoidescatch per site per night ranged from 4 to 45,875 individuals.Culicoides imicolawas dominant at low altitude andC. kibatiensisat high altitude. A marked seasonality was observed for the three other species with annual variations. Twelve groups of variables were tested. It was found that presence and/or abundance of all fiveCulicoidesspecies were driven by common parameters: rain, temperature, vegetation index, forested environment and host density. Other parameters such as wind speed and farm building opening size governed abundance level of some species. In addition,Culicoidespopulations were also affected by meteorological parameters and/or vegetation index with different lags of time, suggesting an impact on immature stages. Taking into account all the parameters for the final hurdle model, the error rate by Normalized Root mean Square Error ranged from 4.4 to 8.5%.ConclusionsTo our knowledge, this is the first study to modelCulicoidespopulation dynamics in Reunion Island. In the absence of vaccination and vector control strategies, determining periods of high abundance ofCulicoidesis a crucial first step towards identifying periods at high risk of transmission for the two economically important viruses they transmit.

Background West Nile virus (WNV) is transmitted by mosquitoes in both urban as well as in rural environments and can be pathogenic in birds, horses and humans. Extrinsic factors such as temperature and land use are determinants of WNV outbreaks in Europe, along with intrinsic factors of the vector and virus. Methods With a multivariate model for WNV transmission we computed the probability of WNV infection in 2014, with July 2014 temperature anomalies. We applied the July temperature anomalies under the balanced A1B climate change scenario (mix of all energy sources, fossil and non-fossil) for 2025 and 2050 to model and project the risk of WNV infection in the future. Since asymptomatic infections are common in humans (which can result in the contamination of the donated blood) we estimated the predictive prevalence of WNV infections in the blood donor population. Results External validation of the probability model with 2014 cases indicated good prediction, based on an Area Under Curve (AUC) of 0.871 (SD = 0.032), on the Receiver Operating Characteristic Curve (ROC). The climate change projections for 2025 reveal a higher probability of WNV infection particularly at the edges of the current transmission areas (for example in Eastern Croatia, Northeastern and Northwestern Turkey) and an even further expansion in 2050. The prevalence of infection in (blood donor) populations in the outbreak-affected districts is expected to expand in the future. Conclusions Predictive modelling of environmental and climatic drivers of WNV can be a valuable tool for public health practice. It can help delineate districts at risk for future transmission. These areas can be subjected to integrated disease and vector surveillance, outreach to the public and health care providers, implementation of personal protective measures, screening of blood donors, and vector abatement activities. Electronic supplementary material The online version of this article (doi:10.1186/s12940-016-0105-4) contains supplementary material, which is available to authorized users.