Submitted to: Veterinary Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/19/2005
Publication Date: 3/22/2006
Citation: Piacenti, A.M., King, D.J., Seal, B.S., Zhang, J., Brown, C.C. 2006. Pathogenesis of newcastle disease in commercial and specific pathogen free turkeys experimentally infected with isolates of different virulence. Veterinary Pathology. 43: 168-178. Interpretive Summary: The effects of Newcastle disesase (ND) on different bird species is variable. The disease in chickens has been well studied, however, the pathogenesis in turkeys is poorly understood and the development of control programs during a ND outbreak in a turkey-producing area will require a more thorough appreciation of the effects of NDV strains of different virulence in this species. We characterized the clinicopathologic features and tissue tropism of NDV in two different breeds of turkeys, using five different strains representing all pathotypes that range in virulence from those used as vaccines that produce either no disease or at most the equivalent of the common cold to those that cause high mortality in susceptible chickens. All turkeys were readily infected by all NDV strains tested, however, clinical disease was more severe in the breed maintained as specific-pathogen-free than in a commercial breed. Infected turkeys shed virus longer and clinical disease was in general less severe than that observed when the same virus strains were studied in chickens. These observations are important considerations for a control program because ND in turkeys may not present as a severe disease and prolonged virus shedding could result in virus spread from these flocks.
Technical Abstract: The pathogenesis of five different Newcastle disease virus (NDV) isolates representing all pathotypes was examined in commercial and specific pathogen free (SPF) turkeys. Experimentally-infected birds were monitored clinically and euthanized, with subsequent tissue collection, for examination by histopathology, by immunohistochemistry (IHC) for the presence of NDV nucleoprotein, and by in situ hybridization (ISH) for the presence of replicating virus. Clinically, the lentogenic pathotype did not cause overt clinical signs in either commercial or SPF turkeys. Mesogenic viruses caused depression in some birds. Turkeys infected with velogenic neurotropic and velogenic viscerotropic isolates showed severe depression, and neurologic signs. There were some distinct differences between commercial and SPF turkeys, highlighting the importance of breed variation. Histologic appearances for all strains had many similarities to lesions observed in chickens inoculated with the various isolates. However, in general, disease among turkeys was less severe than in chickens, and turkeys could be considered a subclinical carrier for some of the isolates.