Research On Molecular Epidemiology Survery Of Porcine Reproductive And Repiratory Syndrome Virus

Porcine reproductive and respiratory syndrome virus (PRRSV) is the causative agent of PRRS which caused reproductive failure in sows and respiratory problems in piglets. It has caused great damages since its being recognized .In recent, some pig farms in Guangxi occur frequently an infectious disease and caused great damages.In this study , we identified 78 sample collected from the farm in Guangxi.Guangdong. Hainan that was positive by RT-PCR.The result is 41 samples are positive. According to the reported complete nucleotide sequences of ATCC VR-2332. a pair of primers were designed to amplify E gene of the 15 samples of the 41 PRRSV positive samples with Primer software.The fragments of coplete E gene were obtained from RT-PCR using RNA exfracted from the virus as template.The product of RT-PCR named E is approximate 668bp in length.The E gene was cloned into PMD18-T vector and sequenced.The results of sequencing showed that complete E gene was 603bp long and had complete open reading frame of E gene which encoded 200 amino acides.The sequence was analyzed homologously in comparison with the E nucleotide sequences of three reference PRRSV, ATCC VR-2332.CH-1a and LV strain.Nucleotide sequences comparison indicated that the 15 samples shared 84.1%~100% .and 85.4%~98.5% 87.1~96.2% 62.5~63.8%with ATCC VR-2332.CH-la and LV strain respectively.The deduced animo acid sequences according to E gene were 83.1 %~95.5% 86.1-95.0% 51.7-57.2% correspondingly. The result showed that PRRSV epidemic strains were significantly genetic divergent from each other, the 15 samplesbelonging to North American genotype.Phylogenetic tree among 15 strains and other 37 PRRSV strains published were obtained by analyzing nucleotide sequences of E gene. GXGG and GDZJ from GuangDong andVR2232 fall into subgrous I . GXWZ, GXWM GXHP GXCZ, GXFS GXBH GXGL, GXBB GXNN and HN-1 HN-2 from HaiNan and CH-la, HZ-X, HB-1. HB-2 belonged to subgrous II ;Two strains GXLZ-1 GXLZ-2 and MD001 located in subgroup IV.The sequnences of different subgroups from different area of GuangXi showed diversity on potential glycosylation sites, antigenic epitope regions and the amino acids associated with virulence of PRRSV by comparison of the deduced amino acids of E gene.In this study,the genetic variability was study by comparing the PRRSV E gene nucleotide. We can understand PRRS epidimiology in south of China, and it should be a good foundation for controling this disease.