Establishment And Application Of A RT-PCR Method For Detection Of Porcine Reproductive And Respiratory Syndrome

In order to understand the prevalence of porcine reproductive and respiratory syndrome (PRRS) in the Guangxi Region, the study designed and synthesized two pairs of specific primers, which are according to the nucleotide homology of the Nsp2gene sequences of classic North American type PRRSV strains, highly pathogenic variation strains and European strains, then established two RT-PCR detection methods. The first method using primers Eur7/Eur8amplified respectively fragments of666bp and572bp from North American and European PRRSV type strains, the second method using primers Pa/Pb amplified fragments of523bp and433bp from the classic North American type PRRSV strains and highly pathogenic variation strains, respectively. By experimental verification, these two methods can’t react with classical swine fever virus, porcine transmissible gastroenteritis virus, porcine epidemic diarrhea virus, swine influenza virus and foot and mouth disease virus type A, type O and type Asia I. The minimum concentration of RNA that can be detected was7.68×10-3μg/ml by primer Eur7/Eur8and7.76×10-5μg/ml by primers Pa/Pb. This show the two RT-PCR methods were good for specificity, sensitivity and reproducibility. The first method can detect quickly and identify accurately the North American type and European type PRRSV strains, the second method can distinguish classic North American type and highly pathogenic variation PRRSV strains. Both methods can be used in combination as PRRSV clinical diagnosis, disease detection and epidemiological investigation of material effective way.The established method were successfully used to do pathogen detection with2355samples from76suspected PRRSV infection farms in eleven cities of Guangxi region during February2012to January2014. The results showed there were324positive samples for PRRSV, positive rate is13.76%. The positive samples of highly pathogenic strains are247, infection rate is10.49%and classical strains are77, infection rate is3.27%. Except for Fangchenggang, other cities all have detected PRRSV, and the infection rate of highly pathogenic strains of North American (NA) type is more than many times NA classical strains. Infection rate is higher in autumn than in spring, summer and winter, and overall, the cases has increased in2013than in2012. The results show that the PRRSV was existing widely in Guangxi region and had a tendency to spread. The highly pathogenic strains are the main type, next is classic strains. European (EU) type strains have not yet been found.