Molecular Epidemiology Research And HY Strain Isolation And Identification Of RRSV In South China

Porcine reproductive and respiratory syndrome is an infective disease which is very harmful to the pig industry.This study is intended to reveal the prevalence of porcine reproductive and respiratory syndrome in the areas of Southern China,and the genetic variation of the virus.Meanwhile,the status of the epidemic strains will be determined and it will provide a basis for prevention and control the disease.This paper mainly contains the following parts:1 Epidemiological investigation of PRRS in South China and genetic evolution analysis of Nsp2 and ORF5 genesPRRSV serological and molecular epidemiology in South China and its nearby areas during 2015 were investigated and analyzed.The results showed that there was no significant difference in the positive rate of antibody in South China,the positive rate of swine antibody was not significant,but the positive rate was higher than 60%.Antigen detection results showed that PRRSV antigen detected in Southern China and the surrounding area is positive,but the positive rate of PRRSV antigen were different in different regions;18 strains Nsp2 amino acid sequence region sequencing were aligned.The results showed that 16 strains were less variation and shareda 91.4%~97.5%similarity to JXA1;1 was similar to QYYZ with a homology of 88.9%;1 had 44 amino acid deleton in 470aa~515aa,and the amino acid was similarity with CH-1a(80.1%);Besides,the ORF5 gene sequences of the 18 strains were measured,16 strains were in the branch of the highly pathogenic strain represented by JXA1,their amino acid sequence homology were 95.0%~99.5%;2 strains were in a small branch which was under the big branch represented by VR-2332 and CH-1a,and were similar to QYYZ strains,with amino acid homology 95.0% ~ 96.0%.2 Investigation and analysis of the South China boars PRRSV molecular epidemiologyELISA diagnostic kit and RT-PCR method were used to detect the serum antigen and antibody of 367 blood samples collected from boars in South China,Nsp2 and ORF5 genes of 66 positive samples were amplified,sequenced and applied phylogenetic analysis.The results showed that among the 332 serum samples from 28 fields in South China of Guangdong Province and Guangxi Province,217 samples from 23 fields were antibody positive,66 samples from 10 fields were antigen positive;among the 35 serum samples from3 fields in Fujian Province and Zhejiang Province,9 samples from one field were antibody positive,none was antigen positive;among the 66 amino acid sequences pushed down by Nsp2 sequence,2 were in the range of VR2332 and CH-1a branches,and the remaining 64 in the high pathogenic strain branch represented by JXA1,the lowest amino acid homology was 77.4%,the highest was 98.1%;66 amino acid sequences pushed down by ORF5 sequence were among the high pathogenic strain branch,the lowest amino acid homology was 93.0%,the highest was 98.5%.3 HY strain separation and purification and the whole genome sequencing of PRRSVTo futherly understand the PRRSV strains in South China,HY strain was purified by plaque and the whole genome was amplified,sequenced and aligned with PRRSV representivep strains.The results showed that the lowest nucleotide similarity of the whole genome between HY and the European strain Lelystad was 60.2%,and was 84.6% with NADC30,89.6% with VR-2332,and 95.1% with the early separated strain CH-1a,99.1%with the highly pathogenic strain JXA1,and the highest similarity of 99.8% with TJbd14-1strain isolated from Henan,China.