Establishment And Premary Application Of RT-PCR For Distinguishing Different Strains Of Porcine Reproductive And Respiratory Syndrome Virus

Porcine reproductive and respiratory syndrome(PRRS) is an acute or sub-acute and highly contagious disease caused by porcine reproductive and respiratory syndrome virus(PRRSV). PRRS significantly affects pregnant sows and breeding pigs. Since the virus spreads readily with high mortality, PRRS becomes the most important swine disease. A variety of strains resulting from PRRS virus variation remain a continuous challenge to control of the disease. The outbreak of highly pathogenic porcine reproductive syndrome virulent strain reported in 2006 had a tremendous impact to the swine industry in China. At present, the major widespread strains in China are all American type, such as the classical virulent strain and the highly pathogenic porcine reproductive syndrome virulent strain. Because of the strain variation, such as clinical manifestations, damage grades and cross-protective vaccine, the significance of controlling PRRSV is to identify the types of current virulent strains in an efficient and accurate way.Porcine reproductive and respiratory syndrome classical strains, highly pathogenic strains and attenuated vaccine strain with gene deletion(TJM-F92) are highly variable in Nsp2 gene. Highly pathogenic virulent strains and TJM-F92 strain are missing 90 and 450 nucleotides, respectively. In this study, primers were designed at its missing ends for RT-PCR method. By this method, the fragment sizes of PCR amplification products for three strains are 1332 bp, 1242 bp and 882 bp. Thus, we can conclude that this method has several desirable properties, such as sensitivity, uniqueness and consistency. By detecting 68 suspected PRRS specimens in Jilin Province, Heilongjiang Province and other regions,13.23% of these copies is porcine reproductive and respiratory syndrome classical strains positive,20.58% is highly pathogenic strains,8.82% is attenuated vaccine strain with gene deletion(TJM-F92). The experiment is aimed at establishing a fast and efficient detection method for PPRS virus. This may be helpful to identify vaccinated pigs and wild virus infected pigs, moreover, to evaluate the effect of the vaccine and the purification of major epidemics.