2018-2019年河南地区猪繁殖与呼吸综合征病毒分子流行病学调查

Molecular epidemiology of porcine reproductive and respiratory syndrome virus in Henan Province from 2018 to 2019

为了解华中地区猪繁殖与呼吸综合征病毒(PRRSV)的流行特点及变异规律,本研究对2018-2019年采自河南18个地市94个猪场的414份猪肺脏、脾脏和淋巴结等样品进行PRRSVRT-PCR检测,并将阳性样品进行ORF5和NSP2基因扩增和序列测定以及遗传进化分析。结果显示,414份病料中共检测出PRRSV阳性样品106份,阳性率为25.48%,其中,豫北地区检出率较高,且2018年11月至2019年2月阳性率明显增加;从阳性样品中扩增得到83个ORF5和31个NSP2基因序列;遗传进化分析表明,检出的PRRSV阳性样品中74株PRRSV属于类NADC30毒株,6株与华南地区主要流行毒株类QYYZ毒株高度相似,2株与商品化活疫苗基因序列高度同源;氨基酸序列比对发现,所检出毒株之间氨基酸同源性差异较大,10株毒株GP5序列在高变区存在插入或缺失,29个NSP2序列存在131位不连续氨基酸缺失,1个NSP2序列与高致病性PRRS疫苗毒株JXA1 NSP2存在相同缺失,1株与经典疫苗毒株RespPRRS MLV完全同源。结果表明,2018-2019年河南地区PRRSV以类NADC30毒株为优势毒株,且NSP2和ORF5基因进一步发生较大变异;同时华南地区主要流行毒株类QYYZ毒株在河南开始增多以及个别活疫苗的使用导致PRRSV的流行趋势更加复杂。因此,加强对PRRSV的流行及遗传变异的持续监测尤为重要,本研究可为PRRS临床诊断、防控以及疫苗研发提供有效的科学依据。

In order to track the epidemic traits and genetic variation of PRRSV in central China,416 samples of lungs,spleens,and lymph nodes collected from 94 pig farms in 18 cities in Henan in 2018 were detected by RT-PCR,then the PRRSV-positive samples were subjected to ORF5 and NSP2 gene amplification and sequencing for genetic evolution analysis.The results showed that a total of 106 samples were PRRSV positive in 416 samples,with a positive rate of 25.48%.Among them,the detection rate was higher in northern Henan,and the positive rate increased significantly from November to February of the following year.Eighty-three ORF5 and 31 NSP2 gene sequences were amplified from PR RSV-positive samples.Genetic evolution analysis showed that the prevalent PRRSV strains in Henan mainly belonged to the American strains.Among the PRRSV-positive samples,74 PRRSV strains belonged to the NADC30-like strains,6 strains were highly similar to the QY YZ-like strains that are mainly spread in South China,and 2 strains are highly homologous to the commercial live vaccine gene sequence.Amino acid sequence alignment found that the amino acid homology among the detected strains differed greatly,and GP5 sequences of 10 strains had in sertions or deletions.In addition,there were 131 discontinuous amino acid deletions in 29 NSP2 sequences,and one NSP2 sequence had the same deletion as the NSP2 of highly pathogenic PRRS vaccine strain JXA1,and one strain was completely homologous with the classic vaccine strain RespPRRS MLV.The results indicated that the PRRSV in Henan region from 2018 to 2019 was dominated by NADC30-like strains,and NSP2 and ORF5 genes were further greatly mutated.At the same time,the main epidemic strains of QY YZ-like in southern China began to increase in Henan.The use of live vaccines made the epidemic trend of PRRSV more complicated.Therefore,it is very important to strengthen the continuous monitoring of PRRSV prevalence and genetic variation.This study can provide evidence for clinical diagnosis,prevention and control of PRRS and vaccine development.