Assessing the risk of mosquito vector-borne diseases in Scotland and their response to environmental change

Mosquitoes are the most important source of vector-borne diseases (VBDs) globally on account of their role in transmitting high burden human diseases like malaria and dengue. They are also responsible for the spread of pathogens from wildlife and livestock to humans ("zoonotic diseases"). While the burden of mosquito VBDs is highest in tropical areas, climate and other environmental changes are driving the expansion of mosquitoes and their pathogens into temperate regions of Europe including the UK. Birds are probably the most important source of emerging mosquito VBDs in Europe (e.g West Nile (WNV) and Usutu viruses (USUV),and have potential to introduce pathogens into the UK during migration. Ability to detect and respond to mosquito VBD emergence in the UK is however hampered by major gaps in national surveillance. Current surveillance is restricted almost entirely to England and Wales; with a near complete absence of data from Scotland. Given Scotland constitutes almost a third of the UK land mass, this gap creates a major vulnerability in national VBD detection and response strategy. We propose to address this here by conducting a comprehensive investigation of mosquitoes and bird populations across Scotland, and assessing their potential for VBD transmission under current and future environmental conditions. First we will conduct mosquito trapping in a range of wetland habitats across Scotland to characterize the distribution, abundance and ecology of potential vector species. We will also collect mosquitoes in a range of urban and rural settings to assess what potential vector species are most likely to be present where people and bird populations overlap. Second, we will take blood samples from wild birds in areas where mosquitoes are being collected to test for pathogens. Bird blood and mosquito samples will be analyzed using a novel molecular method that can test for the presence of up to 80 different pathogens in a single test. We will test samples for a range of VBDs including zoonotic pathogens that have been reported in England and other parts of Europe (e.g., WNV, USUV, Sindbis virus, Western Equine Encephalitis virus, Tahyna Virus), veterinary (avian Pox and avian malaria) and human pathogens (e.g., dengue, malaria, chikungunya virus). Third, we will collect Culex pipiens, one of the most important mosquito vector species in Europe, from sites across Scotland and assess their ability to transmit viruses in experimental infection studies conducted under controlled laboratory conditions. Finally, we will use the data collected above to develop models that predict where potential mosquito vector species and their pathogens are most likely to be found in Scotland under current and future climatic conditions. These models will be used to predict the likelihood of WNV and other zoonotic VBDs becoming established throughout the UK under current or future conditions. In combination, this research will considerably enhance national capacity to understand and mitigate the growing threats posed by VBDs throughout the UK. The project will also enable the establishment of a network and knowledge exchange between academia and government. This will provide a solid foundation for future collaboration on One Health Research and vector-borne disease research within and beyond Scotland.

Climate and other environmental change are driving the expansion of mosquito vector borne diseases (VBDs) into areas of Europe previously unsuitable for transmission; with many being derived from avian populations. This presents a growing risk of VBD establishment in the UK due to presence of competent vectors and infection in local birds. Ability to detect and respond to emergence is however constrained by major gaps in national surveillance; with current activities restricted almost entirely to England and Wales. In contrast, almost no data on mosquito and avian populations is available for Scotland despite the known presence of potential vector species. We propose to address this gap by conducting a comprehensive investigation of mosquito vectors and avian reservoir populations in Scotland, with the goal of assessing potential for VBD transmission under current and future environmental conditions. We will conduct nationwide surveillance of mosquitoes over 2 years in geographically and ecologically representative habitats. We will also sample mosquitoes and blood samples from birds across a rural-urban gradient reflecting variation in where humans are likely to be exposed. Using a novel micro-fluidic PCR approach, samples will be tested for multiple zoonotic pathogens that have been reported in England and mainland Europe (e.g., West Nile and Usutu Virus), and VBDs of conservation (e.g avian pox) and public health concern (Chikungunya, dengue). Culex pipiens, the most important mosquito vector species in Europe, will be collected from Scottish population and tested for arboviral transmission competence under controlled laboratory conditions. In combination, this data will be used to develop risk maps for mosquito vectors and human exposure, and model the likelihood of zoonotic VBD establishment in Scotland under current or future conditions. The main outcome will be considerable enhancement of capacity to mitigate the growing threat of mosquito VBDs in the UK.