Comparison of RT-PCR and DFA methods for detecting classical swine fever virus

A pair of primers for RT-PCR to detect the classical swine fever virus(CSFV) were synthesized according to the published genome sequences of CSFV strains.After the RT-PCR method was established and optimized,15 clinic specimens were detected for CSFV by RT-PCR in comparison with the direct immunofluoresence assay (DFA).The result indicated that a 509 bp specifical fragment was obtained from the CSFV vaccine strains by RT-PCR with the sensitivity reaching 10 pg of CSFVRNA.Negative results were obtained from porcine reproductive and respiratory syndrome virus(PRRSV),porcine parvovirus(PPV),pseudorabies virus(PRV) and porcine circovirus Ⅱ(PCV2).The nucleotide sequence homology of RT-PCR products was 95%-99% of the other CSFV strains.The positive detection rate of the 15 clinic specimens reached 66.7% by RT-PCR,as compared to 60.0% by DFA.The two method's coincidence rate was 80%.These results indicated that the RTPCR method was more sensitive than DFA,and that both methods were suitable for rapid detection of CSFV.