Spatio-temporal Analysis of the Genetic Diversity of Arctic Rabies Viruses and Their Reservoir Hosts in Greenland

There has been limited knowledge on spatio-temporal epidemiology of zoonotic arctic fox rabies among countries bordering the Arctic, in particular Greenland. Previous molecular epidemiological studies have suggested the occurrence of one particular arctic rabies virus (RABV) lineage (arctic-3), but have been limited by a low number of available samples preventing in-depth high resolution phylogenetic analysis of RABVs at that time. However, an improved knowledge of the evolution, at a molecular level, of the circulating RABVs and a better understanding of the historical perspective of the disease in Greenland is necessary for better direct control measures on the island. These issues have been addressed by investigating the spatio-temporal genetic diversity of arctic RABVs and their reservoir host, the arctic fox, in Greenland using both full and partial genome sequences. Using a unique set of 79 arctic RABV full genome sequences from Greenland, Canada, USA (Alaska) and Russia obtained between 1977 and 2014, a description of the historic context in relation to the genetic diversity of currently circulating RABV in Greenland and neighboring Canadian Northern territories has been provided. The phylogenetic analysis confirmed delineation into four major arctic RABV lineages (arctic 1–4) with viruses from Greenland exclusively grouping into the circumpolar arctic-3 lineage. High resolution analysis enabled distinction of seven geographically distinct subclades (3.I – 3.VII) with two subclades containing viruses from both Greenland and Canada. By combining analysis of full length RABV genome sequences and host derived sequences encoding mitochondrial proteins obtained simultaneously from brain tissues of 49 arctic foxes, the interaction of viruses and their hosts was explored in detail. Such an approach can serve as a blueprint for analysis of infectious disease dynamics and virus-host interdependencies. The results showed a fine-scale spatial population structure in Greenland arctic foxes based on mitochondrial sequences, but provided no evidence for independent isolated evolutionary development of RABV in different arctic fox lineages. These data are invaluable to support future initiatives for arctic fox rabies control and elimination in Greenland.北极圈沿岸国家，尤其是格陵兰地区，人畜共患的北极狐狂犬病的时空流行病学相关研究仍较为匮乏。既往分子流行病学研究曾提示存在某一特定的北极狂犬病病毒（Rabies Virus, RABV）谱系（arctic-3），但受限于当时可用样本量较少，无法对狂犬病病毒开展深入的高分辨率系统发育分析。然而，要在格陵兰岛制定更有效的直接防控措施，需从分子层面深入了解当前流行的狂犬病病毒的演化特征，并明晰该疾病在当地的历史流行情况。本研究通过结合全基因组与部分基因组序列，对格陵兰地区北极狂犬病病毒及其储存宿主北极狐的时空遗传多样性展开调查，从而解决了上述问题。研究团队获取了1977年至2014年间采集自格陵兰、加拿大、美国（阿拉斯加）及俄罗斯的79条北极狂犬病病毒全基因组序列，借此阐明了格陵兰与加拿大北部邻近地区当前流行狂犬病病毒的遗传多样性相关的历史背景。系统发育分析确认北极狂犬病病毒可划分为4个主要谱系（arctic 1–4），其中格陵兰地区分离的病毒全部归入环极地arctic-3谱系。高分辨率分析进一步区分出7个具有明显地理特征的亚分支（3.I – 3.VII），其中2个亚分支同时包含格陵兰与加拿大分离的病毒。本研究同时从49份北极狐脑组织中提取了病毒全基因组序列以及宿主编码线粒体蛋白的序列，通过联合分析深入探究了病毒与宿主之间的相互作用。该研究方法可为传染病动态及病毒-宿主相互依存关系的分析提供参考范式。研究结果显示，基于线粒体序列，格陵兰北极狐存在精细的空间种群结构，但未发现不同北极狐谱系内狂犬病病毒发生独立隔离演化的证据。本研究所得数据可为格陵兰地区未来开展北极狐狂犬病防控与根除工作提供极为宝贵的支撑。