A vector excreta surveillance system (VESS) to support the rapid detection of vector-borne diseases

全球一半以上的人口面临致命和使人衰弱的病媒传播疾病（VBD）的风险。包括疟疾、登革热、丝虫病和许多其他疾病在内的VBD每年造成100万人死亡，并使社区陷入经济困境。虽然控制VBDs的许多努力都取得了成功，但我们正在应对全球化、杀虫剂耐药性和气候变化的挑战。寨卡病毒的传播是这些因素如何促进VBD快速扩张的一个非常相关的例子。世界卫生组织呼吁开展更多的研究，以改善传染病监测，以便我们能够预防和控制新出现和重新出现的疾病。幸运的是，在提供病媒控制和大规模药物管理等干预措施以防治这些疾病方面出现了新的政治和财政势头。早期检测系统将允许快速反应，以帮助遏制传播，但这些方法可能是昂贵的，是许多发展中国家所无法达到的。我们已经开发了一种低成本的VBD监测工具，使我们能够检测社区中VBD的存在。蚊子吃人的时候会携带病原体。如果蚊子是一个合格的载体，病原体将继续在蚊子体内发展，蚊子在一两周后变得具有传染性。我们已经证明，当非病媒蚊子摄入受感染的血液时，它们会在接下来的几天内将病原体DNA排泄到粪便中。当病媒摄取受感染的血液时，它们也会分泌少量的病原体DNA。病媒排泄物监测系统收集蚊子排泄物，用于筛查病原体DNA。为了特定疾病的监测或研究，使用多种商业或自制诱捕器中的一种主动或被动收集蚊子。我们已对盛蚊杯进行了修改，在分类和保存之前，可以将蚊子放在盛蚊杯中。我们在蚊子休息的地方下面加入了一个超疏水衬里，它将排泄物集中到一个小水库或漏斗中，然后沉积在特殊的防腐剂上。这是对目前监测方法的重大改进，因为我们能够一次筛选非常大的蚊子池。在这一过程中不使用蚊子样本，因此有机会将这种方法与其他监测活动结合起来。非病媒的作用特别有用，因为它可以在没有物种特异性收集的情况下筛查其他苍蝇传播的疾病（包括导致利什曼病、河盲症、昏睡病的寄生虫）。在我们的实验室研究中，我们已经成功地检测到了疟疾、引起淋巴丝虫病的丝虫和引起动物锥虫病的锥虫的DNA。该提案旨在加纳的一个村庄实地测试这种方法，我们已经描述了疾病流行，蚊子物种和当地生态。我们将使用三种不同的诱捕器类型，以便确定哪种物种和生命阶段（吸血休眠蚊子或准备产卵的妊娠蚊子）对检测排泄物中的寄生虫DNA最敏感。我们会比较从蚊粪池和从个别蚊尸检获的样本所作的检测。我们还打算将这种方法扩展到检测蚊媒病毒西尼罗河病毒、登革热病毒、基孔肯雅病毒和寨卡病毒中的病毒颗粒。发展中国家的疾病控制计划可以采用这种方法，以监测各种血液传播病原体的存在，而无需采集参与者的血液或单独处理蚊子。

More than half of the global population is at risk for deadly and debilitating vector-borne diseases (VBD). VBDs, which include malaria, dengue, filariasis and many others, cause 1 million deaths each year and leave communities in economic hardship. While many efforts to control VBDs have been successful, we are working against the challenges of globalisation, insecticide resistance and climate change. The spread of Zika virus is a very relevant example of how these factors have fostered the rapid expansion of VBDs. The World Health Organization has called for more research to improve infectious disease surveillance so that we can prevent and control emerging and re-emerging diseases. Fortunately, there has been renewed political and financial momentum to provide interventions such as vector control and mass drug administration to combat these diseases. An early detection system would allow for a rapid response to help contain the spread, however these approaches can be costly and are out of reach of many developing nations.We have developed a low cost, VBD surveillance tool which allows us to detect the presence of VBDs in a community. Mosquitoes pick up pathogens when they feed on a person. If the mosquito is a competent vector, the pathogen will go on to develop within the mosquito body and the mosquito becomes infective a week or two later. We have shown that when non-vector mosquitoes ingest infected blood, they excrete the pathogen DNA in their faeces over the next few days. When vectors ingest infected blood, they also excreta small amounts of pathogen DNA. The vector excreta surveillance system (VESS) collects mosquito excreta for the purposes of screening for pathogen DNA. Mosquitoes are actively or passively collected using one of many commercial or home-made trap types for the purposes of disease-specific surveillance or research. We have made a modification to mosquito holding cups, where mosquitoes may be held prior to sorting and preservation. We have included a super hydrophobic lining below where mosquitoes rest which concentrates the excreta into a small reservoir or a funnel which deposits onto special preservative. This is a significant improvement over current monitoring methods because we are able to screen very large pools of mosquitoes at once. The mosquito samples are not used in the process so there are opportunities to integrate this method with other surveillance activities. The role of non-vectors is particularly useful since it would enable screening of other fly-borne illnesses without species-specific collections (including the parasites that cause leishmaniasis, river blindness, sleeping sickness.) There is scope for further development of excreta collection from a passive trap which would eliminate the need to actively collect the mosquitoes.In our lab based studies we have successfully detected DNA from malaria, the filarial worm that causes lymphatic filariasis, and a trypanosome species that causes animal trypanosomiasis. This proposal aims to field-test this approach in a village in Ghana where we have already characterised disease prevalence, mosquito species and local ecology. We will use three different trap types so allow us to determine which species and life-stage (bloodfed resting mosquitoes, or gravid mosquitoes ready to lay eggs) is the most sensitive for detecting parasite DNA in the excreta. We will compare the detection from our pools of excreta with the detection from individual mosquito carcasses. We also aim to extend this methodology to the detection of viral particles from the mosquito-borne viruses West Nile, dengue, chikungunya and Zika.This is an approach that disease control programmes in developing countries could implement in order to monitor the presence of a diverse range of blood-borne pathogens without having to collect blood from participants or process mosquitoes individually.