PRRSV Separation Appraisal In Changchun Area And Establishment Of Differential Diagnosis Methods

Porcine reproductive and respiratory syndrome virus (PRRSV) is a kind of RNA virus which leads to reproductive failure in pregnant sows and piglets. PRRSV is divided into two genotypes including Europe type LV strain and American type VR-2332strain. A strain named PRRSV Changchun CC-13was successfully isolated by cell culture in this study. The CC-13strains were cultured for30generation and the TCID50was stable in10-60/0.1mL.The Nsp2and GP5protein genes (ORF5) of PRRSV CC-13strain was amplified by RT-PCR, respectively with the two specific primers designed according to the corresponding gene sequences of various PRRSV representative strains in GeneBank. The sequence homology and phylogenetic relationship of the isolated CC-13strain and others in domestic and foreign were comparatively analyzed by sequencing Nsp2gene and mapping the phylogenetic tree of and PRRSVGP5protein gene. The results showed that the isolated strains had high homology with China’s highly pathogenic PRRSV strain, which belonged to the American type high strain variation.Clinically, in order to rapidly and effectively distinguish between the high and low pathogenic PRRSV, the Nsp2gene sequences of the high and low pathogenic PRRSV were amplified, respectively with the two specific primers designed according to the feature that there were30amino acid discontinuous deletion in the high pathogenic Nsp2gene. The lengths were644bp and734bp, respectively. The lowest titer was0.1TCID50in susceptibility test. Sixty samples from Changchun and its surrounding area were blindly inspected by this method and10highly pathogenic PRRSV samples were confirmed. This method was compared with the RT-PCR diagnosis method of N protein gene and the results were consistent. This indicated that the method had high accuracy. The RT-PCR method established in this study had specificity, sensitivity and repeatability and could quickly and accurately distinguish between high and low pathogenic PRRSV. This method will provide a simple technical means for the rapid diagnosis and epidemiological investigation of PRRSV in clinic.