Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/1997
Publication Date: N/A
Citation: Interpretive Summary: Newcastle disease virus (NDV; avian paramyxovirus type 1) isolates were recovered from imported exotic birds confiscated following importation into the United States, from water birds in the U.S. and from poultry. Geographically these birds probably originated from Central and South America, Asia and Africa. The NDV isolates were initially characterized as highly virulent due to a short mean death time in embryonated chicken eggs. The isolates were typed as neurotropic or viscerotropic velogenic by intracloacal inoculation of adult chickens. Intracerebral pathogenicity index (ICPI) values for the virulent NDV isolates ranged from 1.54 to 1.90, compared to a possible maximum value of 2.0. All virulent isolates had a dibasic amino acid motif in the fusion protein cleavage site sequence required for host systemic replication. Specific sequence differences were detected surrounding the fusion protein cleavage site and the matrix protein nuclear localization signal, indicating evolution of highly virulent NDV. Phylogenetically, these isolates were categorized with other highly virulent NDV that caused outbreaks in California poultry during 1972 and in cormorants in the U.S. in 1992 and Canada during 1990 and 1992. All these isolates are genetically related to NDV obtained previously from exotic birds that may have APMV1/chicken/Australia/AV/32 or a related virus as a possible progenitor.
Technical Abstract: Newcastle disease is a highly contagious illness of birds capable of causing large economic losses in commercial poultry. Genetic information was used diagnostically to type NDV isolates from exotic birds imported into the United States from 1986 to 1996. The viruses examined were genetically similar and related to a virus that caused outbreaks of Newcastle disease in southern California commercial poultry during the 1970's and in a north central U.S. flock of unvaccinated domestic turkeys during 1992. These NDV isolates, although similar, did vary enough genetically to indicate evolution of the virus. Also, it appears that multiple lineages of NDV occur that circulate among free-living birds that continue to threaten U.S. poultry.