Submitted to: Veterinary Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/30/1998
Publication Date: N/A
Citation: Interpretive Summary: Newcastle disease virus is a highly contagious viral pathogen of chickens. It is vaccinated for with live-virus in the poultry industry. Outbreaks of highly virulent Newcastle disease require reporting to regulatory agencies at the national and international level. Viral isolates can be categorized according to how severe an infection they cause in chickens. Highly virulent Newcastle disease viruses produced systemic disease throughout th chicken. Disease was very evident in the spleen and intestine of some birds, while other exhibited nervous signs. Less virulent Newcastle disease virus isolates did not produce disease that could be detected visually. However, using biochemical techniques presence of virus could be detected in the air sac and heart. This occurred even when birds were infected with vaccine virus. Consequently, live Newcastle disease viruses used for vaccination can be found more extensively in chickens than previously thought. This may allow for secondary bacterial infections to develop following vaccination of chickens for Newcastle disease.
Technical Abstract: Groups of 4-week-old White Rock chickens were inoculated intraconjunctivally with 9 isolates of Newcastle disease virus (NDV) representing all pathotypes. Birds were monitored clinically, and euthanized sequentially, with collection of tissues for histopathology and in situ hybridization to determine sites of viral replication. Disease was smost severe with velogenic viscerotropic pathotypes and was characterized by aute systemic illness with extensive necrosis of lymphoid areas in the spleen and intestine. Viral nucleic acid was detected extensively in multiple tissues. Velogenic neurotropic isolates caused a central nervous system disease despite detection of minimal amounts of viral nucleic acid in neural tissue. Mesogenic and lentogenic pathotypes caused no overt disease yet viral nucleic acid was present in myocardium and air sac epithelium following infection with these isolates. Compromise of air sac and myocardium may predispose to secondary infection and/or decreased production in mesogen and lentogen-infected chickens.