Efficacy of a Newcastle Disease Vaccine Developed from Korean Strain NDRL0901 in Protecting against Recently Emerged Newcastle Disease Viruses in Southeast Asia

New Newcastle disease viruses (NDVs) have been circulating among poultry flocks in several Southeast (SE) Asian countries since the mid-2000s. This study analyzes whether the NDV vaccine strain, NDRL0901, protects against genotype VIIh of NDV. The efficacy of the NDRL0901 vaccine was tested in week-old and threeweek- old specific pathogen free (SPF) chickens. Week-old chickens that had been vaccinated had geometric mean hemagglutination inhibition (HI) titers of 24.1 to 24.7 two weeks after vaccination. The vaccinated birds were completely protected against potentially fatal clinical disease from both the MY3519/2010 and VN5/2007 NDV strains, which were administered via eye drops. No virus was detected in the vaccinated birds, regardless of the challenge virus. When three-week-old SPF chickens were vaccinated, the birds had geometric mean HI titers of 26.3 two weeks after vaccination. The NDRL0901 vaccine provided complete clinical protection against fatal challenges from the NDV isolate, KN5/2011, which was administered via the intramuscular route. No virus shedding was detected in the vaccinated birds after administration of the challenge virus. Our results indicate that locally developed NDV vaccines using NDRL0901 vaccine strain could provide complete protection against the emergent NDV genotype VII in SE Asia. (C) 2017 PVJ. All rights reserved