贵州省猪戊型肝炎的分子流行病学调查

Molecular epidemiological investigation of swine hepatitis E virus in Guizhou Province

采集贵州省戊型肝炎病毒(hepatitis E virus,HEV)抗体阳性的6个猪场新鲜猪粪便样品216份,提取RNA,通过RT-nPCR扩增HEV ORF2基因,对阳性PCR产物进行克隆和测序,采用MEGA5.05软件进行序列比对,构建系统发生树,并经流行病学分析,调查了贵州省猪群的HEV感染情况及基因型。结果显示,HEV主要感染1月龄以上的未成年猪群;粪样采集的6个猪场均不同程度(5.88%～56.52%)地检出HEV RNA阳性,总体阳性率为22.69%(49/216),场群阳性率为100%(6/6);不同类型猪场(养殖户型和养殖场型)HEV RNA阳性率(分别为41.10%和13.29%)差异具有统计学意义(P<0.01),养殖户之间及养殖场之间的阳性率差异无统计学意义(P>0.05),但随着饲养时间的延长,这2种类型猪场的粪便HEV RNA检出率呈上升趋势;测序36个PCR阳性分离株(占73.5%),序列一致性为91.1%～100%,与HEV禽型及Ⅰ、Ⅱ、Ⅲ、Ⅳ型的一致性分别为52.4%～55.4%、75.2%～77.9%、73.6%～75.9%、72.7%～79.1%、83.2%～95.6%,系统发生分析显示与Ⅳ型在同一分支上,属于基因Ⅳ型。结果表明,贵州省猪群普遍存在HEVⅣ型感染。

In order to investigate the infection rate and genotype of hepatitis E virus（HEV） in Guizhou Province,a total of 216 pig fecal samples were collected from 6 anti-HEV IgG positive pig farms.Total RNA was extracted from the samples and reverse transcribed to cDNA.HEV ORF2 gene was then amplified from the cDNA using nested polymerase chain reaction（PCR） with positive products cloned and sequenced.Phylogenetic tree was constructed based on the nucleotide sequences of samples using MEGA 5.05 software.Finally,HEV RNA positive rates were epidemiologically analyzed.Results showed that HEV RNA positive rate of the 6 farms ranged from 5.88% to 56.52% with a overall prevalence of 22.69%（49/216）.The prevalence in different farms with different sizes and standards was statistically significant（P0.05）,so did the herds and age.A total of 36（73.5%） swine HEV isolates were sequenced.It was found that different strains shared 91.1% to 100% nucleotide sequence identities.The identity of the sequenced samples to HEV avian genotype and Ⅰ,Ⅱ,Ⅲ,Ⅳ genotype were 52.4% to 55.4%,75.2% to 77.9%,73.6% to 75.9%,72.7% to 79.1% and 83.2% to 95.6%,respectively.Phylogenetic analysis revealed that the 36 swine HEV isolates were on the same branch with genotypeⅣ,therefore they belonged to HEV genotype Ⅳ.