Prior to the emergence of H3N8 canine influenza virus (CIV) and the latest avian-origin H3N2 CIV, there was no evidence of a circulating canine-specific influenza virus. Molecular and epidemiological evidence suggest that H3N8 CIV emerged from H3N8 equine influenza virus (EIV). This host-range shift of EIV from equine to canine hosts and its subsequent establishment as an enzootic CIV is unique because this host-range shift was from one mammalian host to another. To further understand this host-range shift, we conducted a comprehensive phylodynamic analysis using all the available whole-genome sequences of H3N8 CIV. We found that (1) the emergence of H3N8 CIV from H3N8 EIV occurred in approximately 2002; (2) this interspecies transmission was by a reassortant virus of the circulating Florida-1 clade H3N8 EIV; (3) once in the canine species, H3N8 CIV spread efficiently and remained an enzootic virus; (4) H3N8 CIV evolved and diverged into multiple clades or sublineages, with intra and inter-lineage reassortment. Our results provide a framework to understand the molecular basis of host-range shifts of influenza viruses and that dogs are potential "mixing vessels" for the establishment of novel influenza viruses.

中文翻译：

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H3N8犬流感病毒的宿主范围转移：对其起源和从马到犬宿主的适应性的系统动力学分析。

在H3N8犬流感病毒（CIV）和最新的禽源H3N2 CIV出现之前，没有证据表明正在传播的犬特异性流感病毒。分子和流行病学证据表明，H3N8 CIV来自H3N8马流感病毒（EIV）。EIV从马宿主到犬宿主的这种宿主范围的转变以及随后被确立为动物感染CIV的现象是独特的，因为这种宿主范围的转变是从一种哺乳动物宿主转变为另一种哺乳动物宿主。为了进一步了解宿主范围的变化，我们使用了所有可用的H3N8 CIV全基因组序列进行了全面的系统动力学分析。我们发现（1）H3N8 EIV出现H3N8 CIV的时间大约在2002年；（2）这种种间传播是由佛罗里达州1进化枝H3N8 EIV的重配病毒引起的；（3）在犬种中，H3N8 CIV有效传播并仍然是一种犬病毒。（4）H3N8 CIV进化并分化成多个进化枝或亚谱系，并在谱系内和谱系间进行重配。我们的结果提供了一个框架，以了解流感病毒宿主范围转变的分子基础，并且狗是建立新型流感病毒的潜在“混合容器”。