Biological Identification of Newcastle Disease Viruses Isolated from Eggs of a Parent Breeder Farm

Among 24 eggs from a meat-type parent breeder chicken flocks with egg-dropping,2 embryos were dead at 8-9 d after incubation.The allantoic fluid from them demonstrated hemagglutination activity.By hemagglutination inhibition(HI) and viral neutralization test in cell culture with mono-antiserum against Newcastle disease virus(NDV),H5-and H9-avian influenza virus(AIV),the agent for HA activity in allantoic fluid of dead embryos were identified as NDV and designated as strains Tengz060104 and Tengz060107.The MDT,ICPI and IVPI for Tentz060104 were 56.4 h,1.88 and 2.67 respectively,and they were 40.8 h,1.88 and 2.79 for Tengz060107.Both two isolated strains can cause symptoms and lesions typical to Newcastle disease in 6 weeks old SPF chickens.The results indicated that two NDV isolates were velogenic virulent strains.In cross HI,Tengz060104 and tengz060107 had 100% homology,but they have only 66.7% and 57.7% antigenic homology with F48E8 strain.This is the first report of isolation of virulent NDV from eggs in China.