Chronic bee paralysis virus: The epidemiology, evolution and mitigation of an emerging threat to honey bees

在英国，无数的授粉昆虫对许多农作物的产量和野生植物的繁殖做出了重大贡献。管理的西方蜜蜂（Apis mellifera）提供移动传粉服务，以补充野生传粉者，提供了这种生态系统服务的很大一部分。在过去的30年里，蜜蜂和野生传粉者都面临着多种相互作用的压力，包括土地利用集约化、农用化学品暴露和寄生虫的影响，这些压力通常在传粉者物种之间共享。这些压力通常是单独考虑的，很少放在一起考虑。新出现的传染病，无论是在种群中新出现的还是在发病率/地理范围上迅速增加的，都有对蜜蜂种群造成重大影响的历史。在这里，我们建议调查蜜蜂中迅速出现的一种疾病，称为慢性麻痹，它会导致个体蜜蜂出现严重症状，并经常导致蜂群损失。英国养蜂人报告了严重的疾病反复爆发，而致病的RNA病毒（慢性蜜蜂麻痹病毒[CBPV]）在几个国家的流行率正在上升。这个项目的目的是促进我们对最近出现的蜜蜂慢性麻痹背后机制的理解，并与专业养蜂人合作，制定新的缓解策略。我们将考虑由于CBPV毒株传播性、环境压力因素、管理措施或共同感染而再次出现的情况，并提出四个相互关联的目标，每个目标都有明确的可检验的假设，以解决问题并提供管理解决方案。首先，我们将监测单个蜂群和养蜂场疾病传播的动态，以了解病毒何时何地与蜂群相关。我们将收集与慢性瘫痪相关的压力源的新病例对照数据，包括成年蜜蜂中病原体的存在；成蜂杀虫剂暴露；天气;本地土地用途；以及养蜂管理。我们将结合结构方程和微观模拟模型来阐明疾病发展的先决条件，目的是强调早期疾病检测方案和制定养蜂管理策略以减轻疾病影响。其次，我们将评估最近出现的慢性瘫痪是否是现代CBPV毒株传播性或毒力变化的结果。通过对具有代表性的历史和最近的样本进行测序，我们将描述基因组水平上的时空序列变化。我们将通过开发CBPV的反向遗传系统来恢复具有传染性的历史毒株，并使用这些试剂来比较过去、现在和未来毒株构成的风险——后者通过产生病毒重组——在病毒基因型之间交换rna。最后，我们将评估CBPV对其他非api传粉媒介构成的风险。第三，我们将研究慢性瘫痪的共应激源，使用受控的体内激发试验，包括已知的（由于恶劣天气和过度拥挤而缺乏觅食）和新发现的（肠道寄生虫N. ceranae）共应激源。我们将评估这些因素对不同基因型菌株的传播和毒力的影响。第四，我们将与蜜蜂农民协会（BFA）密切合作，该协会代表英国各地的专业蜜蜂农民，将研究成果转化为管理慢性麻痹的改进专业实践。我们已经确定了一系列潜在的知识交流机会，以探索从我们的实验中产生的数据。这一工作规划将逐步改变我们对慢性麻痹疾病发展、病毒进化和传粉媒介共同压力源的理解，并产生必要的生物学数据和建模工具，以制定知情的管理做法。

In the UK, a myriad of pollinating insects contribute significantly to the yield of many agricultural crops and the reproduction of wild plants. Managed Western honey bees (Apis mellifera) offer mobile pollination services to compliment wild pollinators, providing a large proportion of this ecosystem service. Both honey bees and wild pollinators have been in severe decline for the past 30 years in the face of multiple interacting pressures that include land-use intensification, agrochemical exposure and the impact of parasites - which are often shared between pollinator species. These pressures are frequently considered in isolation and rarely together.Emerging infectious diseases, either newly appearing or rapidly increasing in incidence/geographic range in a population, have a history of causing large impacts on honey bee populations. Here we propose to investigate a rapidly emerging disease in honey bees, known as chronic paralysis, which causes severe symptoms in individual honey bees and often leads to colony loss. UK bee farmers are reporting severe repeated disease outbreaks and the causative RNA virus (Chronic bee paralysis virus [CBPV]), is increasing in prevalence in several countries. The purpose of this project is to advance our understanding of the mechanisms behind the recent emergence of chronic paralysis in honey bees, and work with professional bee farmers to develop new mitigation strategies. We will consider re-emergence as the result of CBPV strain transmissibility, environmental stressors, management practices or co-infection and propose four interlinked objectives, each with clear testable hypotheses, to tackle the problem and deliver management solutions. First, we will monitor the dynamics of disease spread in individual colonies and apiaries to understand where/when the virus becomes associated with the colony. We will gather new case-control data on stressors associated with chronic paralysis to include the presence of pathogens in adult bees; pesticide exposure in adult bees; weather; local land use; and apiary management. We will use a combination of structural equation and microsimulation modelling to elucidate the pre-requisite stressors for disease to develop, with the aim of highlighting early disease detection protocols and developing apiary management strategies to mitigate disease impact. Second, we will assess whether the recent emergence of chronic paralysis is the result of shifts in the transmissibility or virulence of modern CBPV strains. We will describe temporal and spatial sequence variation at the genomic level, by sequencing representative historic and recent samples. We will recover infectious historic strains by developing a reverse genetic system for CBPV, and use these reagents to compare the risk posed by past, current and future strains - the latter by generating virus reassortants - where RNAs are exchanged between virus genotypes. Finally, we will assess the risk posed by CBPV to other non-Apis pollinators. Third, we will investigate co-stressors of chronic paralysis using controlled in vivo challenge tests to include known (lack of foraging due to poor weather and overcrowding) and newly characterised (the gut parasite N. ceranae) co-stressors. We will assess the impact of these factors on transmission and virulence for different genotypic strains.Fourth, we will work closely with the Bee Farmers' Association (BFA) - who represent professional bee farmers from across the UK - to translate research outcomes into improved professional practices when managing chronic paralysis. We have identified a series of potential knowledge exchange opportunities to explore as data arises from our experiments. This programme of work will provide a step-change in our understanding of chronic paralysis disease development, virus evolution and pollinator co-stressors, as well as generating the necessary biological data and modelling tools to develop informed management practices.