Isolation and Identification of Velogenic Newcastle disease virus of 13 Strains and Their Biological Characteristics

13 strains of Newcastle disease virus(NDV),11 from vaccinated chickens and 2 from pigeons,were isolated from Heilongjiang Province during 2004-2005.All isolates' mean death time(MDT) of embryonated eggs,interacerebral pathogenicity index(ICPI),hemagglutination spectrum of erythrocytes, and hemagglutination-separation reactions were tested.The results showed that MDT of all NDV isolates were between 36.8 hours and 73.6 hours,ICPI were between 1.51 and 2.00,belonged to velogenic NDV.All 13 strains can agglutinate the erythrocytes of chicken and human O type.However,their ability of agglutinating erythrocytes of swine,horse,cow,rabbit and guinea pig were variable.Accept from HLJ-12-04,the hemagglutinin of lentogenic strains were stable to heat and belonged to slow type of agglutination-separation,virulent strains were not stable to heat and belonged to fast type of agglutination-separation.