Ecology of Powassan/Deer tick virus in eastern New York State

描述(由申请人提供)：鲍瓦桑病毒(POWV)是一种北美壁虱传播的黄病毒(黄病毒科；黄病毒)，与在亚洲和欧洲发现的旧大陆壁虱传播脑炎(TBE)病毒有关。对分离株的系统发育分析表明，POWV有两个谱系，原型POWV主要由库克伊蚊传播，另一种抗原变异体--鹿虱病毒(DTV)由肩部硬蜱传播。虽然已经在各种哺乳动物中发现了POWV和DTV的感染，但这些物种中的哪一种是重要的宿主尚不清楚。在西尼罗河病毒进入北美后，增加了对人类的监测，改进的诊断试剂表明，在北美，人类严重感染POWV/DTV的流行率增加。这项研究的总体目标是阐明这种新出现的黄病毒的传播动力学，并为了解风险提供基础。我们的假设是，POWV，特别是其抗原变异体DTV，代表了一种新出现的壁虱传播的病原体，由于美国东北部壁虱种群的迅速增长，这种病原体对人类构成了越来越大的风险。综合的现场和实验室研究将：(1)确定线虫白纹伊蚊及其脊椎动物宿主在地方性疫源地的环境负担；(2)确定哪个宿主(S)应对感染硬蜱媒介负责；(3)进一步描述白喉病毒(和DTV)的生物学和生态学特征；以及(4)评估鸟类作为追逐硬蜱的潜在病毒来源的作用。这项初步研究将为今后深入了解POWV和DTV之间的时空遗传差异、传播活动的地理范围、共喂作用以及强大的载体和宿主能力实验提供基础和指导。 与公共卫生有关：波瓦桑脑炎是由波瓦桑病毒及其抗原变异体--鹿虱病毒引起的，尽管罕见，但由于其严重性质，对公共卫生具有重大意义。它与重大的长期发病率有关，包括严重的神经后遗症，病死率为10%-15%。由于目前还没有针对鲍瓦桑脑炎的疫苗或特效疗法，因此了解病原体的生态学以及这种病毒如何与壁虱媒介和脊椎动物宿主相互作用是很重要的。

DESCRIPTION (provided by applicant): Powassan virus (POWV), a North American tick-borne flavivirus (Flaviridae; flavivirus), is related to Old World tick-borne encephalitis (TBE) viruses found in Asia and Europe. Phylogenetic analyses of isolates indicated two lineages of POWV, prototype POWV transmitted predominantly by Ixodes cookei, and an antigenic variant, deer tick virus (DTV), transmitted by Ixodes scapularis. Although infections with POWV and DTV have been detected in various mammals, which of these species act as important reservoirs is unknown. Increased human surveillance following the introduction of West Nile virus into North America, and improved diagnostic reagents have demonstrated increased prevalence in North America of serious infection with POWV/DTV in humans. The overall goals of this study are to elucidate the dynamics of transmission of this emerging flavivirus and to provide the foundation for understanding risk. Our hypothesis is that POWV, and especially its antigenic variant, DTV, represent an emerging tick-borne pathogen that presents an increasing risk to humans as a consequence of burgeoning tick populations in the northeastern US. Integrated field and lab studies will (1) determine the environmental burden of POWV in ticks and their vertebrate hosts at enzootic foci; (2) determine which host(s) is responsible for infecting tick vectors; (3) further characterize the biology and ecology of POWV (and DTV); and (4) assess the role of birds as potential sources of virus for questing ticks. This pilot study will provide the foundation and guidance for future exhaustive efforts to understand spatial/temporal genetic differences between Lineage 1 (prototype POWV) and Lineage 2 (DTV) Powassan virus, geographic scope of transmission activity, role of co-feeding, and robust vector and host competence experiments. PUBLIC HEALTH RELEVANCE: Powassan encephalitis, caused by Powassan virus and its antigenic variant, deer tick virus, is of significant public health importance because of its serious nature in spite of its rarity. It is associated with significant long- term morbidity including severe neurologic sequelae with a case-fatality rate of 10%-15%. Because there is no vaccine or specific therapy for Powassan encephalitis, it is important to understand the ecology of the causative agent and how this virus interacts with its tick vectors and vertebrate hosts.