Anatid herpesvirus 1 (AHV-1, CHv virulent strain) was obtained from the Avian Disease Research Center of Sichuan Agricultural University (Yaan, Sichuan, China). Virus stock was added onto the surface of the cell layer which was about 90% confluency at time of infection and the maximum virus titers could usually be obtained 48 h postinfection. DNA extraction from AHV-1 infected DEF cells and tissues of AHV-1 infected ducks were performed by using TIANamp Genomic DNA extracting kit (Tiangen Corporation, Beijing, China) according to the manufacture's instructions.