2014年~2019年PRRSV主要流行毒株在我国的变化

The changes of mainly endemic PRRSV in China during 2014—2019

为了研究2014年至2019年PRRSV在我国的流行变化情况,本研究分别检测了2014年6月~2019年8月全国17个省、市和自治区及某大型养猪集团2007份和338份疑似PRRSV感染的病料。结果显示,共检出PRRSV阳性病料650份,测定了486株ORF5基因、441株nsp2基因和122株全基因组序列。遗传演化分析显示,2014年~2019年共检测到6种基因亚型的PRRSV,分别是I型PRRSV、HP-PRRSV、NADC30-like PRRSV、NADC34-like PRRSV、QYYZ-like PRRSV和RespPRRS MLV-like PRRSV。经统计分析显示,2016年以前除检测到1株NADC30-like PRRSV外,其余全部是HP-PRRSV;2016年后HP-PRRSV检出比率逐渐降低,NADC30-like PRRSV检出比率逐渐升高,且2016年后已超过HP-PRRSV,成为我国主要的流行株。QYYZ-like PRRSV的检出数量增多,其广泛流行于我国的华南地区。其它类型的PRRSV检出比率较低,呈现散发或局部流行。此外,近年来,PRRSV的细胞嗜性已经发生明显变化,绝大多数的病毒株无法在体外分离培养。因此,我国养殖企业针对PRRSV流行株的变化应及时调整防控策略,同时加大对PRRSV生物学特性变化机制的研究。本研究对了解我国PRRSV的流行状况及防控具有重要的指导意义。

To investigate the prevalence of PRRSV in China,2007 and 338 samples that suspected PRRSV infection were collected from 17 provinces,cities,autonomous regions and a large-scale pig company from June 2014 to August 2019 in this study.The results showed that 650 samples were positive for PRRSV infection,and 486 ORF5 genes,441 nsp2 genes and 122 complete genomes were further sequenced.Phylogenetic analysis showed that there were six subgenotypes of PRRSV,including type I PRRSV,HP-PRRSV,NADC30-like PRRSV,NADC34-like PRRSV,QYYZ-like PRRSV and Resp PRRS MLV-like PRRSV.Statistical analysis suggested that all the PRRSVs,except one NADC30-like PRRSV,belonged to HP-PRRSV before 2016;the positive rate of HP-PRRSVs and NADC30-like PRRSVs was reducing and raising after 2016,respectively.Moreover,the positive rate of NADC30-like PRRSVs was higher than HP-PRRSVs after 2016 which implying that NADC30-like PRRSVs has become the major epidemic strain.In recent years the positive number of QYYZ-like PRRSVs was increasing and widely distributedin south China.While,other types PRRSVs were occasionally detected,and showing dissemination or local prevalence.In addition,most of the PRRSVs were not able to cultivate using PAM or Marc-145 cells in vitro,which means the cellular tropism of PRRSVs might have changed.Thus,the pig companies should adjust their control strategies in time according to the endemic PRRSV strains.Meanwhile,the mechanism of the changes in biological characteristics of PRRSV should be further investigated.This study has great significance to understand the prevalence of PRRSV and its prevention and control in China.