Abstract: To establish a rapid differential diagnosis method of porcine reproductive and respiratory syndrome virus (PRRSV) classic and variant strains, a pair of primers corresponding to the highly conserved regions of Nsp2 gene of PRRSV genome were synthesized according to the sequences of PRRSV on GenBank, a RT-PCR method for detection and differentiation of classical and variant PRRSV was established. A fragment of 549 and 459 bp was amplified from genomic RNA of classical or high-pathogenic PRRSV respectively, no specific products were achieved after differentiating detection of porcine originated viral pathogens including HCV, JEV, PEDV, TGEV, PRV, PCV2 and PPV. The RT-PCR could detect 1 pg RNA of classical and 0.1 pg RNA of variant PRRSV respectively. The established RT-PCR method had good specificity, sensitivity, repeatability, could accurately and quickly identify the classical and variant PRRSV, it provided a kind of efficient, rapid, specific and sensitive detection method for clinical diagnosis, disease detection and molecular epidemiology of material such as porcine reproductive and respiratory syndrome virus.

Key words: porcine reproductive and respiratory syndrome virus; classical virus; variant virus; RT-PCR; differential diagnosis