河南省及周边省份猪群中大面积感染猪伪狂犬病毒的病因分析

Investigation of Etiology of Massive Infection with Porcine Pseudorabies Virus in Henan and Neighboring Provinces

2011年初开始,猪伪狂犬病（pseudorabies,PR）在河南省及周边省份再次突然出现严重暴发。为查明原因,应用PRV gE抗体ELISA检测试剂盒对2011年1月至2013年5月送检的16 800份猪血清、905份猪流行性腹泻病毒（Porcine epidemic diarrhea virus,PEDV）＂返饲＂病料和56份PR基因缺失活疫苗分别进行野毒感染检测,通过PCR方法对11株PRV新流行毒株的TK、gE基因进行序列测定与分子特征分析,同时对这些毒株的毒价测定、免疫攻毒保护试验以及疫苗效价测定等开展研究。结果显示,PRV野毒感染阳性猪场检出率高达68.06%,血清总阳性率为38.47%,种母猪、种公猪、后备猪和商品猪的阳性率分别为40.12%、30.88%、54.67%和26.52%;新流行毒株聚在同一进化分支,均属于强毒株,但毒力较经典毒株变化不大,gE基因长度均为1 787bp,TK基因长度均为963bp,与不同年代中国参考毒株的核苷酸、氨基酸序列同源性分别为98.2%~99.8%、97.1%~99.8%和98.9%~99.6%和97.5%~99.4%;商品疫苗对新流行毒株的保护率为100%;疫苗和＂返饲＂病料中,PRV野毒阳性检出率分别为0%和40.44%。研究结果证实,2011年后河南省及周边省份猪群中,PRV野毒感染率大幅攀升;PRV新流行毒株的主要毒力基因并未发生明显变异;疫苗中未存在PRV野毒污染,而且可完全抵抗新流行毒株的攻击;种公猪、后备猪普遍带毒和PEDV＂返饲＂病料中严重污染野毒是造成2011~2013年间河南省及周边省份猪群中PRV大面积感染和疫情暴发的主要因素。

In early 2011,the serious outbreak of porcine pseudorabies virus（PRV）infection suddenly recurred in Henan and neighboring Provinces.To investigate the etiology of massive infection with PRV,16 800serum samples,905porcine epidemic diarrhea virus（PEDV）back-feeding tissues,and 56PR gene deleted live vaccines were colleted from January 2011to May 2013to detect PRV field infection using a PRV gE antibody test kit.The gE and TK genes of 11new epidemic PRV strains were sequenced by PCR,and their molecular characteristics were analyzed.Moreover,virus titer determination,protective test against PRV,and vaccine potency testing were performed.The results showed that the detection rate of PRV field infection-positive pig farms was 68.06%,and the overall positive rate of PRV field infection in serum was 38.47%;the positive rates in breeding sows,breeding boars,reserve pigs,and commercial pigs were 40.12%,30.88%,54.67%,and 26.52%,respectively.The new epidemic strains were in the same evolutionary branch and belonged to the virulent strain group.Compared with the classical PRV strain,the virulence of new epidemic strains changed a little.The length of gE gene was 1 787bp,and the length of TK gene was 963bp.The nucleotide homologies of gE and TK genes to Chinese reference strains were 98.2%-99.8%and 98.9%-99.6%,respectively,and the amino acid homologies were 97.1%-99.8%and 97.5%-99.4%,respectively.Commercial vaccine had a 100% protective effect against the new epidemic strains.The positive rate of PRV field infection was 0%in vaccine and 40.44%in back-feeding tissues.The results confirmed that PRV field infection rates were rising sharply among pigs in Henan and neighboring Provinces after 2011.The main virulence genes of new epidemic PRV strains did not change significantly over the years.PR gene deleted live vaccines had no PRV field infection and could completely resist the attack of new strains.The virus carriage of breeding boars and reserve pigs and the serious PRV field infection in PEDV back-feeding tissues were the main causative factors for massive infection with PRV and epidemic outbreak in Henan and neighboring Provinces from 2011to 2013.