A test of using RT-PCR means to distinguish the virulent and avirulent strains of NDV

A reverse transcriptase-polymerse chain reation(RT-PCR) was sta blished to differentiate virulent and avirulent NDV strains.Three sets of speci fic primers used in RT-PCR were designed according to the sequences of NDV with various virulence from the Genebank and the sequence differences at F0 cleavage sites between virulent and avirulent strains. The method was rapid, specific an d simple for manipulation. It could not only be used for differential diagnosis of NDV strains derived from the inoculated chicken embryo, but also be used for differentiation of the sample of tissue homogenized liquid. It was suggested th at the RT-PCR method was potential for diagnosis of ND, differential diagnosis of NDV and epidemiological investigation.