Studies on the immunization against field strain after live Newcastle disease virus vaccination

뉴캣슬병 생독백신 접종 후 야외 분리 바이러스에 대한 면역성 조사

This Study was conducted to determine vaccination programs for the control of Newcastle Disease(ND) in chickens and investigate protective effect against Newcastle disease virus (NDV) after live ND vaccination. Maternal HI antibody titer level of chickens according to day(age) 1, 7, 14, 21, 28 and 35 were decreased gradually as 7.10$\pm$0.74, 6.57$\pm$0.74, 3.71$\pm$1.25, 2.20$\pm$1.03, 1.20$\pm$1.23 and 0.50$\pm$0.71. As a result of HI test and ELISA, both chickens vaccinated with VG/GA strain live vaccine at 1-day-old and chickens not vaccinated do not have antibody titer for protection against NDV at 14-day-old. Except for LaSota strain vaccine, in case of vaccination with VG/GA spray and VG/GA, B1 and LaSota strain drinking water at 14-day-old, the protective effect was 100% in chickens inoculated NDV($10^{7.2}$ $EID_{50}$/50${\mu}\ell$, eye drop) at 21-day-old, but not 10～50% at 28-day-old. These data suggest that live NDV vaccination should be given at 10-day-old 20-25day-old for protect against NDV at periodic outbreaks of ND caused by velogenic viscerotropic NDV in the environment of a farm.