Vector competence of British mosquitoes to flaviviruses

英国的蚊子能把病毒传染给牲畜和人吗？英国蚊子是否能够传播节肢动物传播的病毒（“虫媒病毒”）还存在很大的不确定性。一方面，英国有一些蚊子种类与虫媒病毒在欧洲大陆的传播有关，其中一些地方的气候和环境与英国相似。另一方面，据了解，蚊子传播的病毒没有在英国传播（除了少数通过昆虫的口器“机械”传播）。此外，据报道，蚊子对不同病毒的能力存在区域差异。因此，目前尚不清楚英国是否有合适的蚊子，但病毒传播的条件不对；我们的蚊子是否不能传播病毒；或者我们的蚊子是否有能力传播病毒，但机会还没有出现。鉴于全球变化对传染病出现的影响，至关重要的是对英国病媒传播虫媒病毒的潜力进行评估，以便在疫情爆发之前或发生疫情时启动知情的缓解程序。此外，蚊子传播虫媒病毒的能力对温度很敏感，这使得这类病毒很可能受到气候变化的影响；为了评估未来的风险，了解温度的影响非常重要。我们在这里的主要目的是确定英国本土蚊子和入侵蚊子是否会被感染并传播影响牲畜和人类的病毒，以及这种能力（如果存在）如何受到温度的影响。据报道，欧洲有10种蚊媒虫媒病毒，其中一些与英国纬度相近。现场观察显示，英国存在潜在的本地媒介，特别是西尼罗病毒（WNV）媒介。2011年，在英国发现西尼罗河病毒的主要媒介之一莫德库蚊（Culex modestus）积极繁殖，这是已知的第一个入侵性蚊子物种的引入和确立。虽然这些蚊子的存在本身就表明存在虫媒病毒传播的风险，但由于这些蚊子传播这些病毒的能力存在遗传和环境差异，因此必须通过详细的实验室实验来进一步支持这些蚊子作为媒介的潜力。虽然几种蚊媒病毒的出现是合理的，但我们选择了日本脑炎病毒（JEV）和西尼罗河病毒在英国蚊子中进行评估。本研究选择乙脑病毒的原因是我们已经感染了来自英国的一种蚊子，并发现这种蚊子能够传播乙脑病毒。虽然乙脑病毒主要发生在亚洲大陆，但确实发生过虫媒病毒的洲际传入，并且随着人类流动性的增加，可能变得更加常见。事实上，最近在欧洲蚊子中报告了乙脑病毒的证据。之所以选择西尼罗河病毒进行这项研究，是因为它可能对英国构成最紧迫的威胁。西尼罗河病毒在全球广泛分布，在非洲、西亚、中亚、中东、欧洲和最近的北美都有发现。该病毒可感染多种蚊子和脊椎动物宿主。由于其在北美和欧洲（特别是法国南部）的传播，以及在欧洲其他地方与英国相似的纬度发生，该病毒对英国具有重大意义。我们将使用一种感染模型，在该模型中，来自野外的蚊子将直接感染最近分离的病毒株。将对蚊子进行评估：它们传播病毒的能力；达到感染所需的病毒剂量；以及温度对其载体能力的影响。

Are British mosquitoes capable of transmitting viruses to livestock and people? There is great uncertainty whether British mosquitoes are capable of transmitting arthropod-borne viruses ("arboviruses"). On one hand, the UK has some mosquito species that are implicated in the transmission of arboviruses in mainland Europe, and the climate and environment in some of these locations are similar to those in the UK. On the other hand, mosquito-borne viruses are not known to have been transmitted in the UK (apart from a small number that are 'mechanically' transmitted on the insects' mouthparts). Furthermore, regional differences in competence of mosquitoes to different viruses have been reported. Therefore, it is not clear whether the UK has the right mosquitoes but the wrong conditions for virus transmission; whether our mosquitoes simply cannot transmit viruses; or whether our mosquitoes are capable of transmitting viruses, but the opportunity has not yet arisen. Given the impact of global change on the emergence of infectious diseases, it is paramount that UK vectors are assessed for their potential to transmit arboviruses, in order to mount informed mitigation procedures in advance of, or in the event of, an outbreak. Furthermore, the ability of mosquitoes to spread arboviruses is sensitive to temperature, making such viruses likely to be affected by climate change; it is important to understand the effects of temperature in order to assess future risks.Our main aim here is to determine whether native British mosquitoes and invasive mosquito species present in the UK can be infected and transmit viruses that affect livestock and humans, and how this ability, if present, is affected by temperature. Ten mosquito-borne arboviruses have been reported in Europe with some at similar latitude to the UK. Field observations have shown potential native vectors, particularly West Nile virus (WNV) vectors, to be present in the UK. In 2011, Culex modestus, a major vector of WNV, was found actively propagating in the UK, representing the first known introduction and establishment of an invasive mosquito species. While the mere presence of these mosquitoes suggests a risk for arbovirus transmission, further support for the potential of these mosquitoes to serve as vectors must be demonstrated in detailed laboratory experiments since there is genetic and environmental variation in the ability of these mosquitoes to transmit these viruses. While the emergence(s) of several mosquito-borne viruses is plausible, we have chosen Japanese encephalitis virus (JEV) and WNV for evaluation in UK mosquitoes. JEV was selected for this study because we have already infected Ochlerotatus detritus, a mosquito from the UK, and found this mosquito able to transmit JEV. Though JEV occurs mostly on the Asian continent inter-continental introductions of arboviruses do occur, and with increased human mobility, may become more common. In fact, evidence for JEV has recently been reported in European mosquitoes. WNV was selected for this study because it arguably poses the most imminent threat to UK. WNV is widely distributed across the globe, being found in Africa, West Central Asia, the Middle East, Europe and recently North America. The virus infects a wide range of mosquitoes and vertebrate hosts. Due to its spread in North America and in Europe, particularly southern France, and its occurrence in similar latitudes to the UK elsewhere in Europe, this virus is of major interest to the UK. We will use an infection model where mosquitoes from the field will be directly infected with recently isolated strains of viruses. Mosquitoes will be assessed for: their ability to transmit virus; the viral dosage required to achieve infection; and the effect of temperature on their vector competence.