Tifton Veterinary Diagnostic and Investigational Laboratory, College of Veterinary Medicine, University of Georgia, PO Box 1389, 43 Brighton Rd, Tifton, GA, 31793, USA.
The Department of Virology, Faculty of Veterinary Medicine, University of Sadat, Sadat City, Egypt.
Virol J. 2018 Aug 2;15(1):118. doi: 10.1186/s12985-018-1027-2.
Canine distemper (CD) is a highly contagious, systemic, viral disease of dogs seen worldwide. Despite intensive vaccination in developed countries, recent reports suggest both the re-emergence and increased activity of Canine distemper virus (CDV) worldwide, including the United States. CDV is an RNA virus of the genus Morbillivirus within the family Paramyxoviridae. Viral genomic RNA encodes six structural proteins. Of the six structural proteins, the hemagglutinin (H) gene has the greatest genetic variation and is therefore a suitable target for molecular epidemiological studies. The majority of neutralizing epitopes are found on the H protein, making this gene also important for evaluation of changes over time that may result in antigenic differences among strains. The aim of this study was to determine the phylogenetic relationship of CDV strains circulating in the US.
Fifty-nine positive canine distemper virus samples collected from dogs from different regions and states from 2014 to 2017 were sequenced with a targeted next-generation sequencing (NGS) method. The sequences of the H, F, and P genes and the matrix-fusion (M-F) intergenic region of the amplified CDVs were analyzed individually.
Sequence analysis of the H gene revealed that there are at least 3 different lineages of CDV currently circulating in the US. These lineages include America-3 (Edomex), America-4, and a clade that was previously reported in association with an outbreak in Wyoming, which was linked to a domestic dog-breeding facility in Kansas in 2010. These lineages differ from the historically identified lineages in the US, including America-1, which contains the majority of the vaccine strains. Genetic differences may result in significant changes to the neutralizing epitopes that consequently may lead to vaccine failure. Phylogenetic analyses of the nucleotide sequences obtained in this study of the F and P genes and the M-F intergenic region with sequences from the GenBank database produced similar findings to the H gene analysis.
The CDV lineages currently circulating in the US differ from the historically identified lineages America-1. Continuous surveillance is required for monitoring circulating CDV strains in the US, to prevent potential vaccine breakthrough events.
犬瘟热（CD）是一种高度传染性、全身性、病毒性疾病，在全球范围内可见于犬类。尽管在发达国家进行了密集的疫苗接种，但最近的报告表明，犬瘟热病毒（CDV）在全球范围内重新出现并更加活跃，包括美国。CDV 是副粘病毒科麻疹病毒属的 RNA 病毒。病毒基因组 RNA 编码六种结构蛋白。在这六种结构蛋白中，血凝素（H）基因具有最大的遗传变异，因此是分子流行病学研究的合适目标。大多数中和表位位于 H 蛋白上，这使得该基因对于评估随时间推移可能导致不同毒株之间抗原差异的变化也很重要。本研究旨在确定在美国流行的 CDV 毒株的系统进化关系。
采用靶向下一代测序（NGS）方法对 2014 年至 2017 年间来自不同地区和州的犬的 59 份犬瘟热病毒阳性样本进行测序。单独分析扩增 CDV 的 H、F 和 P 基因以及基质-融合（M-F）基因间区的序列。
H 基因序列分析显示，目前至少有 3 种不同的 CDV 谱系在美国流行。这些谱系包括美国-3（Edomex）、美国-4 以及一个与 2010 年堪萨斯州一家犬繁殖场相关的怀俄明州爆发有关的分支，该分支与怀俄明州爆发有关，与堪萨斯州的一家犬繁殖场有关。这些谱系与美国历史上确定的谱系不同，包括包含大多数疫苗株的美国-1。遗传差异可能导致中和表位发生重大变化，从而导致疫苗失败。本研究中对 F 和 P 基因以及 M-F 基因间区的核苷酸序列与 GenBank 数据库中的序列进行的系统进化分析得出的结果与 H 基因分析相似。
目前在美国流行的 CDV 谱系与历史上确定的美国-1 谱系不同。需要进行持续监测，以监测美国流行的 CDV 株，防止潜在的疫苗突破事件。
