2020—2022年湖北省生猪屠宰场伪狂犬病病毒的分离鉴定及遗传进化分析

Prevalence and Phylogenetic Analysis of Pseudorabies Virus within Pig Slaughterhouses in Hubei Province of China during 2020-2022

旨在监测湖北省生猪屠宰场中伪狂犬病病毒(pseudorabies virus,PRV)的流行情况。采集2020—2022年湖北省4个区域(鄂东、鄂北、鄂西、鄂中)共9个县市不同规模屠宰场的1795份血液样品和2081份肺样品(肺、肺门淋巴结),分别使用靶向PRV gE基因的ELISA和PCR方法检测血清中的抗体和肺样品中的病原,同时对阳性样品进行病原分离鉴定、全基因组测序和遗传进化分析。血清学检测结果显示,共有104份样品为阳性,平均阳性检出率为5.79%。病原学检测结果显示,共有82份样品为阳性,平均阳性检出率为3.94%。按不同因素对检出率进行分析,显示抗体和病原都在春季检出率最高,分别为18.57%和9.74%;湖北省东部的抗体检出率最高(10.77%),中部的病原检出率最高(4.93%);A类小型屠宰场的病原和抗体检出率都显著高于其他3个类型,分别为16.28%和6.01%。从病原阳性样品中共分离到PRV 17株,经全基因组和gB、gC、gE基因遗传进化分析结果显示均属于基因Ⅱ型变异株,与Bartha、NIA-3、Becker等早期国外分离株处于不同的遗传进化分支。其中HBXG疑似发生了基因Ⅰ型毒株与基因Ⅱ型毒株的重组,与早期报道的重组病毒HuB1/CHN2017同处于独立的clade2.2遗传分支。综上所述,湖北省屠宰场关联的猪场中主要流行PRV变异毒株,且免疫过疫苗的猪场还在发生疫苗株与野毒的重组与变异,因此本研究对PRV的持续监测与新型疫苗的研发工作有十分重要的意义。

The aim of this study was to monitor the prevalence of pseudorabies virus(PRV)in pig slaughterhouses in Hubei Province.A total of 1795 blood samples and 2081 lung samples(lung and hilar lymph nodes)were collected from slaughterhouses of different sizes in nine cities in four regions(East Hubei,North Hubei,West Hubei,Central Hubei)of Hubei Province from 2020 to 2022,and antibodies in serum and pathogens in lung samples were detected by ELISA and PCR targeting the PRV gE gene.Virus isolation and identification,whole genome sequencing,and phylogenetic analysis were performed on positive tissue samples.Serological detection results showed that 104 serum samples were positive,with an average positive detection rate of 5.79%.The results of pathogen detection showed that 82 lung samples were positive,with an average positive detection rate of 3.94%.According to different factors,The highest detection rates of antibody and pathogen were 18.57%and 9.74% respectively in spring.The antibody detection rate of eastern Hubei was the highest(10.77%),and the pathogen detection rate of central Hubei was the highest(4.93%).The detection rates of pathogens and antibodies in grade A small slaughterhouses were significantly higher than those in the other three types,reaching 16.28% and 6.01%,respectively.A total of 17 PRV strains were isolated from PRV positive samples.The results of genetic evolution analysis of whole genome and gB,gC and gE genes showed that the isolates belonged to genotype Ⅱ variants,which were in different genetic evolution branches from early foreign isolates such as Bartha,NIA-3 and Becker.HBXG is suspected to be a recombinant strain of genotype Ⅰ and genotype Ⅱ,and is in the same clade2.2 genetic branch as the earlier reported recombinant HuB1/CHN2017.In conclusion,mutant strains were mainly prevalent in pig farms associated with slaughterhouses in Hubei Province.At the same time,recombination and mutation of vaccine strains and wild viruses were still occurring in vaccinated pig farms.Therefore,this study is of great significance for the continuous monitoring of PRV and development of novel vaccines.