The homology of the sequences, reported and registered in GenBank of different strains of Avian influenza virus(AIV), Newcastle disease virus(NDV), Classical swine fever virus(CSFV)and Food and mouth disease virus(FMDV), was respectively analyzed and compared with each other. According to the properties of these viruses, the conservative domain of M gene for AIV, F gene for NDV, 5′non-coding domain end for CSFV and 2B gene for FMDV were selected for PCR amplification. In order to prevent the formation of co...