Evaluating Effect of Woody Plant Encroachment on Tick-borne Pathogens in the South Central United States

项目摘要/摘要 美国中南部是人类扁虱传播疾病(TBD)发病率最高的地区之一，如斑点 发热群立克次体病和埃立克次体病。然而，它是关于地球生态的研究最少的地区之一。 扁虱的种类和宿主，以及它们与人类引起的环境变化的联系。无处不在的形式 包括美国中南部在内的全球正在进行的人为造成的土地覆盖变化正在侵蚀 在草地和灌丛中的木本植物(木本植物入侵；WPE)。WPE的生态影响 (例如，小气候和节肢动物群落的改变)反映了其他土地覆盖的机制 变化影响病原体的传播，包括壁虱传播的病原体(Tbps)。然而，WPE的 生态系统的大规模改造使其从根本上不同于其他研究得很好的木本植物 森林砍伐和非本土灌木入侵等变化。一个几乎没有研究过的后果 WPE是其潜在的基础性作用，它影响着蜱媒的分布和森林的时空格局。 TBP传输。我们的长期目标是阐明WPE如何影响中南部地区的壁虱传播疾病 并将这一知识应用于更好地预测人类疾病风险并针对公共卫生资源和 有利于人类健康的WPE管理。我们的总体目标是通过以下方式评估WPE之间的关系 东部红柏(ERC；Juniperus virginiana)，美国中南部的主要入侵物种，以及 俄克拉荷马州的TBP传输系统(那里的WPE范围是美国其他地区的5-7倍)。我们的 中心假设是，WPE对生态系统造成的许多变化促进了空间扩张和 关键媒介持续存在，增加多种病原体的媒介感染率。要解决这个问题 假设，我们提出了两个目标：1)量化与ERC入侵相关的扁虱丰富度和多样性； 2)评估TBP感染患病率与ERC侵袭的关系。初步研究表明 关键种类(美洲Amblyomma americanum和Dermacentor aribilis)和被感染的壁虱数量 SFG立克次体和埃立克斯体侵袭的细菌数量较高。这项研究将包括两年的 现场采集了代表4个ERC侵占阶段的40个地点的扁虱，包括没有ERC的对照地点。 将对5种病原体进行鉴定和检测，并分析ERC分期是否与 扁虱的多样性、丰度和TBP流行率。这项研究是创新的，因为全球范围内没有研究 在整个疾病系统框架下考虑WPE的影响。实现我们的目标将增加 了解WPE对TICS和TBP传播动力学的影响；未来的研究将解决其他 作用机制包括WPE对宿主的影响和扁虱与宿主的相互作用。这项研究将提供关键的 通过提供基于土地覆盖评估的壁虱控制策略来改善公众健康的信息 特点，重点布局公共卫生资源，制定WPE管理。

PROJECT SUMMARY/ABSTRACT The south-central U.S. has among the highest human incidences of tick-borne diseases (TbDs) like spotted fever group rickettsiosis and Ehrlichiosis. Yet, it is one of the least-studied regions with regard to the ecology of tick species and hosts, and their associations with human-caused environmental change. A pervasive form of human-caused land cover change ongoing globally, including in the south-central U.S., is encroachment of woody plants in grasslands and shrublands (woody plant encroachment; WPE). WPE’s ecological impacts (e.g., alteration of microclimates and arthropod communities) mirror mechanisms by which other land cover changes influence transmission of pathogens, including tick-borne pathogens (TbPs). However, WPE’s wholesale transformation of ecosystems makes it fundamentally different from other well-studied woody cover changes like deforestation and non-native shrub invasions in forests. A virtually unstudied consequence of WPE is its potential foundational role in influencing distributions of tick vectors and spatiotemporal patterns of TbP transmission. Our long-term goal is to clarify how WPE affects tick-borne diseases in the south-central U.S., and to apply this knowledge to better predict human disease risk and target public health resources and WPE management that benefit human health. Our overall aim is to assess relationships between WPE by eastern redcedar (ERC; Juniperus virginiana), the primary encroaching species in the south-central U.S, and TbP transmission systems in Oklahoma (where WPE extent is 5-7x greater than elsewhere in the U.S.). Our central hypothesis is that the many WPE-caused changes to ecosystems facilitate spatial expansion and persistence of key tick vectors and increase rates of vector infection for multiple pathogens. To address this hypothesis, we propose 2 objectives: 1) Quantify tick abundance and diversity relative to ERC encroachment; and 2) Evaluate links between TbP infection prevalence and ERC encroachment. Preliminary studies indicate that numbers of key tick species (Amblyomma americanum & Dermacentor variabilis), and of ticks infected with SFG rickettsia and Ehrlichia spp., are higher with ERC encroachment. This study will include 2 years of field sampling ticks at 40 sites representing 4 ERC encroachment stages, including control sites with no ERC. Ticks will be identified and tested for 5 pathogen groups, and we will analyze whether ERC stage is related to tick diversity, abundance, and TbP prevalence. This study is innovative because no research globally has considered effects of WPE under a whole-disease system framework. Addressing our objectives will increase understanding of WPE’s impact on ticks and TbP transmission dynamics; future research will address other mechanisms including WPE effects on reservoir hosts and tick-host interactions. This study will provide critical information that improves public health by informing tick control strategies based on assessment of land cover characteristics, and by focusing distribution of public health resources and enactment of WPE management.