Transmission of Ehrlichia chaffeensis by Adult Ticks

描述（由申请方提供）：人类单核细胞埃立克体病（HME）是迄今为止美国报告的最流行的人畜共患埃立克体病，其控制方法依赖于更好地了解查菲埃立克体（病原体）与其蜱宿主之间的相互作用。已有研究表明，钝眼蜱属、革蜱属和硬蜱属等几种硬蜱都能自然感染E. chaffeensis。虽然检测E.在自然暴露的蜱中的chaffeensis表明这些蜱对感染的易感性，但不能证明它们将这种病原体传播给易感脊椎动物宿主的能力。在确定合格媒介之前，必须满足的主要标准是，疑似媒介对节肢动物传播的病原体进行反复实验传播。这一特殊应用的目的是确定蜱传播E。chaffeensis，是确定蜱物种和病原体收购的情况下，导致有效的实验传播这种病原体。本项目的中心假设是，室内感染的成年雄性硬蜱是更有效的E。chaffeensis比成年女性或transstadially感染成年男性蜱。这一中心假设将通过实现具体目标进行检验，具体目标集中在（1）开发用于大肠杆菌的PCR检测方法; chaffeensis的敏感性足以在实验感染的蜱个体内检测病原体;（2）E. chaffeensis传播; chaffeensis对多个宿主的成年男性蜱。提出这项研究的理由是，它将导致更好地了解不同蜱种和收购方案在传播E。在自然条件下的Chaffeensis此外，一旦有效的传输周期被确定，一个实验传输模型将可使我们能够调查之间的相互作用E。chaffeensis及其蜱宿主。这项工作是创新的，因为它质疑了这种蜱传病原体只会跨场传播的教条，但这种范式将在场内和跨场传播的情况下进行客观的测试。除了建立传播模型外，还将确定几种潜在媒介的能力，这对于确定犬是否可能成为人类感染E.对HME的准确诊断和预防具有重要意义。总的来说，这些结果预计将对人类（和动物）健康产生重大的积极影响，因为它们将导致理解E。chaffeensis和其他可能密切相关的病原体在人类和国内的主机。

DESCRIPTION (provided by the applicant): Approaches to the control of human monocytic ehrlichiosis (HME), the most prevalent zoonotic ehrlichial disease reported in the USA to date, rely on better understanding of interactions between Ehrlichia chaffeensis, the etiologic agent, and its tick host. It has been demonstrated that several ixodid genera, including Amblyomma, Dermacentor and Ixodes, can be naturally infected with E. chaffeensis. Although detection of E. chaffeensis in naturally exposed ticks indicates susceptibility of these ticks to infection, it does not demonstrate their ability to transmit this pathogen to a susceptible vertebrate host. Repeated experimental transmission of an arthropod-borne pathogen by the suspected vector(s) is chief among the criteria that must be fulfilled before the competent vector(s) is (are) incriminated. The objective of this particular application, which is an essential step in determining the mechanisms behind tick transmission of E. chaffeensis, is to identify tick species and pathogen-acquisition scenarios that lead to effective experimental transmission of this pathogen. The central hypothesis of this project is that intrastadially infected adult male ixodid ticks are more effective experimental vectors of E. chaffeensis than adult female or trans-stadially infected adult male ticks. This central hypothesis will be tested through fulfillment of specific aims focused on (1) development of a PCR assay for E. chaffeensis that is sensitive enough to detect the pathogen within individual experimentally infected ticks, (2) intrastadial and transstadial tick-transmission of E. chaffeensis and (3) transmission of E. chaffeensis to multiple hosts by adult male ticks. The rationale for the proposed research is that it will lead to better understanding of the potential importance of different tick species and acquisition scenarios in the transmission of E. chaffeensis under natural conditions. Furthermore, once effective transmission cycles are identified, an experimental transmission model will be available to enable us to investigate interactions between E. chaffeensis and its tick host(s). This work is innovative because it questions the dogma that this tick borne pathogen is only transmitted transstadially, but this paradigm will be tested objectively with both intrastadial and transstadial transmission scenarios. In addition to development of a transmission model, the competence of several potential vectors will be determined, which is important for determining whether dogs could be a source of human infection with E. chaffeensis and for accurate diagnosis and prevention of HME. Collectively, these outcomes are expected to have significant positive effects on human (and animal) health, because they will lead to understanding the mechanisms responsible for transmission of E. chaffeensis and perhaps other closely related pathogens among human and domestic hosts.