BIOLOGICAL AND MOLECULAR CHARACTERIZATION OF NEWCASTLE-DISEASE VIRUS (NDV) FIELD ISOLATES WITH COMPARISONS TO REFERENCE NDV STRAINS

Fifty-seven Newcastle disease virus (NDV) isolates from chickens, turk eys, a rhea, a parrot, and an anhinga were pathotyped and characterize d by monoclonal antibody (mAb) inhibition profile, elution rare, and h emagglutinin thermostability. Nucleotide sequence analysis of portions of the fusion protein and matrix protein genes of the parrot isolate was done for comparison with prior sequence analysis of the anhinga is olate and NDV reference strains. Seven of the 43 chicken isolates were recovered from flocks in Canada. The remaining isolates, including 11 from turkeys, were isolated in the United States. All isolates except that of the anhinga were of low virulence by mean death time in embry os, intracerebral pathogenicity index, and/or intravenous pathogenicit y index procedures and were classified as lentogens. The anhinga isola te was more virulent than the other strains and was pathotyped as a me sogen. However, nucleotide sequence analysis of the anhinga isolate ha d revealed a homology with the virulent cormorant isolates of 1992 rat her than the classical U.S. mesogens characterized by the Roakin strai n. Variability was evident among the lentogenic isolates. Two isolates from turkeys had mAb profiles that differed from B1 and La Sera refer ence and vaccine strains, and 38% (21/56) of the isolates had more the rmostable hemagglutinins than those reference strains. There was no ev idence that any of the isolates from poultry were more virulent than t he lentogenic pathotype.