Culicoides midges are abundant hematophagous flies that vector arboviruses of veterinary and medical importance. Dramatic changes in the epidemiology of Culicoides-borne arboviruses have occurred since 1998, including the emergence of exotic viruses in northern temperate regions, increases in global disease incidence, and enhanced virus diversity in tropical zones. Drivers may include changes in climate, land use, trade, and animal husbandry. New Culicoides species and new wild reservoir hosts have been implicated in transmission, highlighting the dynamic nature of pathogen-vector-host interactions. Focusing on potential vector species worldwide and key elements of vectorial capacity, we review the sensitivity of Culicoides life cycles to abiotic and biotic factors. We consider implications for designing control measures and understanding impacts of environmental change in different ecological contexts. Critical geographical, biological, and taxonomic knowledge gaps are prioritized. Recent developments in genomics and mathematical modeling may enhance ecological understanding of these complex arbovirus systems.

The emergence of multiple strains of bluetongue virus (BTV) and the recent discovery of Schmallenberg virus (SBV) in Europe have highlighted the fact that exotic Culicoides-borne arboviruses from remote geographic areas can enter and spread rapidly in this region. This review considers the potential for this phenomenon to impact on human health in Europe, by examining evidence of the role of Culicoides biting midges in the zoonotic transmission and person-to-person spread of arboviruses worldwide. To date, the only arbovirus identified as being primarily transmitted by Culicoides to and between humans is Oropouche virus (OROV). This member of the genus Orthobunyavirus causes major epidemics of febrile illness in human populations of South and Central America and the Caribbean. We examine factors promoting sustained outbreaks of OROV in Brazil from an entomological perspective and assess aspects of the epidemiology of this arbovirus that are currently poorly understood, but may influence the risk of incursion into Europe. We then review the secondary and rarely reported role of Culicoides in the transmission of high-profile zoonotic infections, while critically reviewing evidence of this phenomenon in endemic transmission and place this in context with the presence of other potential vector groups in Europe. Scenarios for the incursions of Culicoides-borne human-to-human transmitted and zoonotic arboviruses are then discussed, along with control measures that could be employed to reduce their impact. These measures are placed in the context of legislative measures used during current and ongoing outbreaks of Culicoides-borne arboviruses in Europe, involving both veterinary and public health sectors.

Since 1998 bluetongue virus (BTV), which causes bluetongue, a non-contagious, insect-borne infectious disease of ruminants, has expanded northwards in Europe in an unprecedented series of incursions, suggesting that there is a risk to the large and valuable British livestock industry. The basic reproduction number,R₀, provides a powerful tool with which to assess the level of risk posed by a disease. In this paper, we computeR₀for BTV in a population comprising two host species, cattle and sheep. Estimates for each parameter which influencesR₀were obtained from the published literature, using those applicable to the UK situation wherever possible. Moreover, explicit temperature dependence was included for those parameters for which it had been quantified. Uncertainty and sensitivity analyses based on Latin hypercube sampling and partial rank correlation coefficients identified temperature, the probability of transmission from host to vector and the vector to host ratio as being most important in determining the magnitude ofR₀. The importance of temperature reflects the fact that it influences many processes involved in the transmission of BTV and, in particular, the biting rate, the extrinsic incubation period and the vector mortality rate.

The appearance of bluetongue virus (BTV) in 2006 within northern Europe exposed a lack of expertise and resources available across this region to enable the accurate morphological identification of species of Culicoides Latreille biting midges, some of which are the major vectors of this pathogen. This work aims to organise extant Culicoides taxonomic knowledge into a database and to produce an interactive identification key for females of Culicoides in the Western Palaearctic (IIKC: Interactive identification key for Culicoides). We then validated IIKC using a trial carried out by six entomologists based in this region with variable degrees of experience in identifying Culicoides. The current version of the key includes 98 Culicoides species with 10 morphological variants, 61 descriptors and 837 pictures and schemes. Validation was carried out by six entomologists as a blind trial with two users allocated to three classes of expertise (beginner, intermediate and advanced). Slides were identified using a median of seven steps and seven minutes and user confidence in the identification varied from 60% for failed identifications to a maximum of 80% for successful ones. By user class, the beginner group successfully identified 44.6% of slides, the intermediate 56.8% and the advanced 74.3%. Structured as a multi-entry key, IIKC is a powerful database for the morphological identification of female Culicoides from the Western Palaearctic region. First developed for use as an interactive identification key, it was revealed to be a powerful back-up tool for training new taxonomists and to maintain expertise level. The development of tools for arthropod involvement in pathogen transmission will allow clearer insights into the ecology and dynamics of Culicoides and in turn assist in understanding arbovirus epidemiology.

The recent emergence of bluetongue virus (Reoviridae: Orbivirus ) (BTV) in northern Europe, for the first time in recorded history, has led to an urgent need for methods to control the disease caused by this virus and the midges that spread it. This paper reviews various methods of vector control that have been employed elsewhere and assesses their likely efficacy for controlling vectors of BTV in northern Europe. Methods of controlling Culicoides spp. (Diptera: Ceratopogonidae) have included: (a) application of insecticides and pathogens to habitats where larvae develop; (b) environmental interventions to remove larval breeding sites; (c) controlling adult midges by treating either resting sites, such as animal housing, or host animals with insecticides; (d) housing livestock in screened buildings, and (e) using repellents or host kairomones to lure and kill adult midges. The major vectors of BTV in northern Europe are species from the Culicoides obsoletus (Meigen) and Culicoides pulicaris (L.) groups, for which there are scant data on breeding habits, resting behaviour and host‐oriented responses. Consequently, there is little information on which to base a rational strategy for controlling midges or for predicting the likely impact of interventions. However, data extrapolated from the results of vector control operations conducted elsewhere, combined with some assessment of how acceptable or not different methods may be within northern Europe, indicate that the treatment of livestock and animal housing with pyrethroids, the use of midge‐proofed stabling for viraemic or high‐value animals and the promotion of good farm practice to at least partially eliminate local breeding sites are the best options currently available. Research to assess and improve the efficacy of these methods is required and, in the longer term, efforts should be made to develop better bait systems for monitoring and, possibly, controlling midges. All these studies will need better methods of analysing the ecology and behaviour of midges in the field than are currently in use. The paucity of control options and basic knowledge serve to warn us that we must be better prepared for the possible emergence of other midge‐borne diseases, particularly African horse sickness.