Establishment of differential diagnostic method for normal and mutant PRRSV strains by RT-PCR

Through analyze the Nsp2 gene of PRRSV published in GenBank nucleotide sequence database,3 primers were designed and one step detected RT-PCR method was established.The result showed that,180 bp specifically fragment and 267 bp fragment were amplified from variant PRRSV and classical form PRRSV.The developed method was sensitive to detect the RNA as low as 1.5 pg.The negative results were found on PRV,CSFV,PCV-2,JEV,CPV,TGEV,SIV.One hundred clinical specimens of sick pigs were tested by the method from 2009 to 2010,26 percent of them were variant PRRSV and 8 percent of them were classical form PRRSV.The results showed that the RT-PCR assay is high specificity,sensiticity and reproducibility,and could be used to differentiate common PRRSV.