Dear Editor,rnNewcastle disease virus (NDV),also known as avian paramyxovirus serotype 1 (APMV-1),is a member of the genus Avulavirus within the family Paramyxoviridae,order Mononegavirales (Miller et al.,2010).Although all isolated NDV strains belong to a single serotype,epidemiological studies have revealed that the genotype Ⅶ strain is currently the most prevalent circulating genotype worldwide and is associated with many of the most recent outbreaks in China since 1997 (Liu et al.,2007).