Author
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King, Daniel |
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Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/29/1996 Publication Date: N/A Citation: N/A Interpretive Summary: Characterization and pathogenicity evaluation of Newcastle disease virus (NDV) isolates from pigeons is difficult. Viruses that typically cause a severe form of the disease and mortality in pigeons usually do not cause severe disease in chickens. Pigeon NDV did cause a severe outbreak of Newcastle disease (ND)in chickens in England, therefore pigeon NDV is a potential hazard to poultry. Characterization tests of U.S. and Canadian isolates revealed that the virus surface protein responsible for cell attachment during infection bound red blood cells at a much lower titer than NDV strains from other birds. Detergent/ether treatment of the isolates enhanced the titer of the attachment protein for use in serological tests. Monoclonal antibodies that differentially inhibit that protein were useful in separating the pigeon isolates into three different antigenic groups. It was learned that a higher dose of pigeon NDV was required to infect chickens and infected chickens shed more virus from th cloaca than from the respiratory tract. Contact with feces is therefore a more likely source of transmission than aerosol. This information will assist diagnosticians in the characterization and differentiation of pigeon NDV from NDV strains from other birds until there is a better understanding of the mechanism of virus adaptation or selection that enhances the chicken virulence of some NDV isolates. Technical Abstract: Nine pigeon avian paramyxovirus type 1 isolates from the U.S. and Canada were characterized and three of the isolates were pathotyped before and after passage in chickens and chicken embryos. Hemagglutination (HA) titers of all isolates were low enough to be negative by rapid plate HA. The HA titers were increased 8- to 32-fold by Tween-ether treatment and treated antigen had the same reactivity as untreated antigen in hemagglutination-inhibition (HI) tests. All isolates had a slow elution rate and a HA thermostability equal or greater than 60 minutes. Mean death times (MDT) in embryos were 99 hours or greater, except for one isolate with a MDT of 81 hours and intracerebral pathogenicity indices of all isolates were greater than 1. Antigenic differences among the pigeon isolates were identified by three different binding patterns in HI tests against a battery of five Newcastle disease virus (NDV) monoclonal antibodies. Pathogenicity enhancement by bird or embryo passage was limited to an intravenous pathogenicity index increase for one of three viruses passaged in embryonated eggs. Cloacal samples collected during chicken passage contained higher virus titers than oral samples. The pigeon isolates reported here have properties that prevent characterization within a single NDV pathotype. Finally, there was no evidence that any of these isolates were highly virulent for chickens. |
