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

描述（由申请人提供）：波瓦桑病毒（POWV）是一种北美蜱传黄病毒（黄病毒科；黄病毒），与在亚洲和欧洲发现的旧大陆蜱传脑炎（TBE）病毒有关。分离株的系统发育分析表明，POWV有两个谱系，一个是主要由cookei硬蜱传播的原型POWV，另一个是由肩胛骨硬蜱传播的抗原变体鹿蜱病毒（DTV）。虽然在各种哺乳动物中发现了POWV和DTV感染，但这些物种中哪些是重要的宿主尚不清楚。西尼罗病毒传入北美后，加强了对人的监测，并改进了诊断试剂，这表明北美人类严重感染POWV/DTV的流行率有所增加。本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，并为理解风险提供基础。我们的假设是，POWV，尤其是它的抗原变体DTV，代表了一种新兴的蜱传病原体，由于美国东北部蜱虫种群的迅速增长，这种病原体对人类的风险越来越大。综合现场和实验室研究将(1)确定蜱虫及其脊椎动物宿主中POWV的环境负担；(2)确定感染蜱虫媒介的宿主；(3)进一步表征POWV（和DTV）的生物学和生态学特征；(4)评估鸟类作为寻找蜱虫的潜在病毒来源的作用。该初步研究将为进一步深入了解波瓦桑病毒谱系1 （POWV原型）和谱系2 （DTV）之间的时空遗传差异、传播活动的地理范围、共食的作用以及强大的媒介和宿主能力实验提供基础和指导。

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.