King D J
Avian Dis. 1986 Oct-Dec;30(4):724-7.
Newcastle disease virus (NDV) hemagglutination-inhibition (HI) titers were determined for serum samples from eight commercial broiler breeder flocks and their progeny. The chickens sampled had been vaccinated and reared by different producers in different regions of the United States. Breeder flocks had the highest number of NDV-positive HI titers (greater than or equal to 1:10). Eighty percent or more of the samples from six of eight breeder flocks were positive; the geometric mean titers (GMTs) for those six breeder flocks ranged from 19 to 92. Only 3 of 8 broiler flocks had an increased frequency of positive titers and higher GMTs after vaccination. The frequency of positive titers was greater than 80% in only 2 of 8 of the oldest broiler flocks. The number of NDV-negative titers (less than 1:10) increased with age in most broiler flocks, even though all had been vaccinated once or more with live NDV vaccines.
测定了来自八个商业肉种鸡群及其后代血清样本的新城疫病毒（NDV）血凝抑制（HI）效价。所采样的鸡由美国不同地区的不同生产商进行了疫苗接种和饲养。种鸡群中NDV阳性HI效价（大于或等于1:10）的数量最多。八个种鸡群中有六个群80%或更多的样本呈阳性；这六个种鸡群的几何平均效价（GMTs）在19至92之间。八只肉鸡群中只有3只在接种疫苗后阳性效价频率增加且GMTs更高。在八只最老的肉鸡群中，只有2只的阳性效价频率大于80%。即使所有肉鸡群都已接种过一次或多次活NDV疫苗，但大多数肉鸡群中NDV阴性效价（小于1:10）的数量随年龄增加。
