中文摘要：

2010—2012年在全国新城疫主动监测中分离并鉴定出6株基因XII型新城疫病毒。这是我国首次发现该基因型病毒。分离到的XII型新城疫病毒全部分布在我国南方地区，多为水禽分离株，仅有1株为鸡源分离株。脑内接种致病指数（ICPI）和分离株F蛋白裂解位点的氨基酸组成证实分离株均为新城疫强毒。进一步的遗传进化分析表明，这6株分离株属于基因XIIb亚型，与南美地区的XII型分离株基因型不同（XIIa亚型）。对于国内新出现的基因XIIb新城疫病毒的来源，仍需要更多的监测数据来证实。目前的监测数据表明，这种在我国新出现的XII型新城疫病毒具有在当地造成地方流行和进一步扩散的风险。

英文摘要：

Six genotype XII Newcastle disease viruses(NDVs)were isolated and identified from active risk-based surveillance during2010-2012.It was the first report of the genotype XII NDVs in China.All viruses were isolated from southern part of China,most of isolates were originated from waterfowl,and only one strain was isolated from chicken.All viruses were proved to be virulent based on the value of ICPI and the cleavage site of F protein.All NDV isolates were clustered into subgenotype XIIb,whereas reference XII NDVs isolated from South America were placed into subgenotype XIIa.More surveillance need to be conducted in order to identify the origin and source of the emerging genotype XII in China.The current monitoring data indicated that the emerging genotype XII viruses not only had the potential to cause ND endemic in local area,but also had high risk to spread into other parts of China.