Hassan Habibi

This study was conducted to assess efficacy of heat-stable I-2 vaccine against Newcastle diseases in vaccinated and vaccinated in contact birds group following challenge against virulent Newcastle disease (ND)virus invillage chicken.Also, toassesswhetherbirds thathavebeenexposed to vaccine virus-shedding, birds were protected against mortality and clinical signs after infection with a virulent strain of the ND virus (NDV). One hundred fifty one-day-old native chickens were divided into seven groups (4 experimental groups of 30 birds/group and 3 control groups (unvaccinated unchallenged, challenged, and just vaccinated). Birds in experimental groups were vaccinated either via drinking water or as food carrier with thermostable I-2 vaccine and then challenged with virulent isolate of NDV (JF820294.1), and eight birds were added as in-contact birds to vaccinated groups. Following challenge, seven extra birds were added to each group as in contact with vaccinated and challenged birds.Survivalrate,clinicalsigns,necropsyfinding,andmean antibody titer were evaluated in different experimental and control groups. Birds vaccinated via drinking water showed 100 % survival rate. However, birds vaccinated with food carrier vaccine showed less than 50 % survival rate. Based ontheresultsobtainedfromthisstudy,itcanberecommended that I-2 vaccination via drinkingwater can effectively prevent ND in village chicken, since I-2 strain has been able to transmit to non-vaccinated-sensitive birds more effectively than velogenic NDV.