title: Virulence of pigeon-origin Newcastle disease virus isolates for domestic chickens.
abstract: The virulence of six pigeon-origin isolates of Newcastle disease virus (NDV) was evaluated before and after passage in white leghorn chickens. Four isolates were defined as pigeon paramyxovirus-1 (PPMV-1) and two isolates were classified as avian paramyxovirus-1 (APMV-1) with NDV monoclonal antibodies. The four PPMV-1 isolates were passaged four times in chickens, and the APMV-1 isolates were passaged only once. Infected birds were monitored clinically and euthanatized. Tissues were collected for histopathology, in situ hybridization with a NDV matrix gene digoxigenin-labeled riboprobe, and immunohistochemistry with an anti-peptide antibody to the nucleoprotein. Mean death time, intracerebral pathogenicity index, and intravenous pathogenicity index tests performed before and after passage in chickens demonstrated increased virulence of the passaged PPMV-1 isolates and high virulence of the original isolates of APMV-1. Sequence analysis of the fusion protein cleavage site of all six isolates demonstrated a sequence typical of the virulent pathotype. Although the pathotyping results indicated a virulence increase of all passaged PPMV-1 isolates, clinical disease was limited to depression and some nervous signs in only some of the 4-wk-old specific-pathogen-free white leghorns inoculated intraconjunctivally. However, an increased frequency of clinical signs and some mortality occurred in 2 wk olds inoculated intraconjunctivally with passaged virus. Histologically, prominent lesions in heart and brain were observed in birds among all four groups inoculated with the PPMV-1 isolates. The behavior of the two pigeon-origin APMV-1 isolates when inoculated into chickens was characteristic of velogenic viscerotropic NDVs and included necro-hemorrhagic lesions in the gastrointestinal tract.
authors.affiliation: Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens 30602-7388, USA.
authors.forename: G D
authors.initials: GD
authors.lastname: Kommers
authors.forename: D J
authors.initials: DJ
authors.lastname: King
authors.forename: B S
authors.initials: BS
authors.lastname: Seal
authors.forename: C C
authors.initials: CC
authors.lastname: Brown
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001483:Base Sequence; D001921:Brain / Q000473:pathology / Q000821:virology; D002642:Chick Embryo; D002645:Chickens; D010856:Columbidae; D006321:Heart / Q000821:virology; D007150:Immunohistochemistry / Q000662:veterinary; D008969:Molecular Sequence Data; D009026:Mortality; D009206:Myocardium / Q000473:pathology; D009521:Newcastle Disease / Q000401:mortality / Q000473:pathology / Q000821:virology*; D009522:Newcastle disease virus / Q000145:classification / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity*; D010802:Phylogeny; D011201:Poultry Diseases / Q000401:mortality / Q000473:pathology / Q000821:virology*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D012692:Serial Passage / Q000662:veterinary; D013047:Specific Pathogen-Free Organisms; D014760:Viral Fusion Proteins / Q000737:chemistry; D014774:Virulence
chemical_list: D000911:Antibodies, Monoclonal; D014760:Viral Fusion Proteins