The Ecology and Classification of Rickettsia Species Phylotype G022, an Uncharacterized Bacterium from Ixodes pacificus Ticks

项目总结/摘要 虽然蜱虫和蜱传疾病病原体已迅速成为对人类和动物的严重和日益增长的威胁， 兽医公共卫生，越来越多的证据表明，许多蜱传疾病由于立克次体感染可能是 在北方美洲，由于其在人类和家畜中的非典型症状，报告不足。硬蜱 在美国的太平洋西海岸，pacificus是致病菌和内共生菌的主要载体。 与在加州其他蜱类中发现的致病性立克次体相比，致病性立克次体的生态学和生物学特征 I.立克次体太平洋大部分地区尚未开发。我们的实验室检测到一种新的立克次体物种，立克次体物种 G_（022）型在寻找I. 2011年、2013年和2020年，北方加州三个县的太平洋小蠊。 由于G 022型在成人I. pacificus和发表的系统发育树， 在其他致病性斑点热群立克次体中的细菌，我们的假设是，G 022型是一种致病性斑点热群立克次体， 立克次体这项拟议的研究最终将作为我们先前关于生态和 致病力的立克次体物种在I.太平洋。我们的研究追求以下具体目标：1）我们将进行一项 调查估计立克次体种G 022型在I. pacificus通过收集 通过实时荧光定量PCR技术检测病原菌; 2）研究立克次体的传播途径 种G 022在I.通过饲养新西兰白色兔收集所有生命阶段的蜱 实时荧光定量PCR检测立克次体; 3）立克次体的增殖和分离 G_（022）型分离物。利用蜱胚胎细胞系和有限稀释法测定太平洋蜱的存活率; 4）我们将进行 利用多位点序列分型技术对立克次体G 022分离株进行分子分型; 5） 调查来自北方加州的家犬中是否存在立克次体属G 022型感染。这 这项研究不仅将导致通过对纯细菌分离株进行分型来正式命名G 022型，而且还使我们能够 为了开始收集有关该细菌传播动力学及其潜在致病性的数据， 我们实验室的研究目标，人类和动物宿主在北方加州。

Project Summary/Abstract While both ticks and tick-borne disease agents have rapidly become a serious and growing threat to human and veterinary public health, mounting evidence indicates that many tick-borne diseases due to rickettsial infection may be under-reported in Northern America because of their uncharacteristic symptoms in humans and domestic animals. Ixodes pacificus is a principal vector for pathogenic and endosymbiotic bacteria on the Pacific West Coast of the United States. Compared to pathogenic rickettsiae identified in other tick species in California, the ecology and biology of pathogenic rickettsiae in I. pacificus remains largely unexplored. Our lab detected a novel Rickettsia species, Rickettsia species phylotype G022, in questing adult ticks of I. pacificus in three counties of Northern California in 2011, 2013, and 2020. Due to phylotype G022’s low prevalence (2-4.5%) in adult I. pacificus and published phylogenetic trees placing the bacterium within other pathogenic spotted fever group rickettsiae, our hypothesis is that phylotype G022 is a pathogenic Rickettsia. The proposed study ultimately serves as a continuation of our previous findings regarding the ecology and pathogenesis of Rickettsia species in I. pacificus. Our research pursues the following specific aims: 1) We will conduct a survey to estimate the prevalence of Rickettsia species phylotype G022 in nymphal ticks of I. pacificus by collecting the nymphs from the field and detecting the bacterium by real-time PCR; 2) We will study transmission routes of Rickettsia species phylotype G022 in I. pacificus by collecting all life stages of the ticks via feeding on New Zealand white rabbits and detecting the bacterium by real-time PCR; 3) We will perform the propagation and isolation of the Rickettsia phylotype G022 isolate from I. pacificus using tick embryonic cell lines and limiting dilution assay; 4) We will perform the molecular typing of the Rickettsia species phylotype G022 isolate by Multilocus Sequence Typing; 5) We will investigate the presence of Rickettsia species phylotype G022 infection in domestic dogs from Northern California. This study will not only result in the official naming of phylotype G022 by typing the pure bacterial isolate, but also enable us to start gathering data on transmission dynamics of the bacterium as well as its potential pathogenicity, the long-term research goal of our lab, to humans and animal hosts in Northern California.