Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 30, 2013
Publication Date: N/A
Technical Abstract: Newcastle disease (ND) is caused by virulent strains of Newcastle disease virus (NDV), and is a devastating disease of poultry worldwide. The intracerebral pathogenicity index (ICPI) is the internationally recognized system used to assess the virulence of NDV strains, with those scoring = 0.7 considered virulent. Although widely deployed, there is no detailed description of lesions and viral distribution occurring in chickens infected with the ICPI method. In this study, a medium-virulence (Anhinga, ICPI 1.45) and one high-virulence (California, 1.75) NDV strain were used in order to evaluate pathology and viral replication (immunohistochemistry, IHC) in the nervous tissue and extra-encephalic sites (spleen) of chickens inoculated with ICPI method. For both strain, results showed that virus replication in the brain occurred in two distinct spatial patterns: 1) surface oriented (ependyma, chorioid plexus, neurons surrounding the ventricular system, meninges, and 2) perivascular (neurons surrounding scattered vessels). Replication was also observed in the spleen, confirming systemic virus replication with both strains. In all cases, IHC staining increased with time after inoculation, and it was more intense and extensive with the California strain. Histologically, lesions were observed mainly in birds infected with the California strain and consisted of neuropil vacuolization, focally extensive demyelination, and splenic necrosis. In conclusion, these results show that ICPI-inoculated chickens suffer from both local (encephalic) and systemic viral replication, and that increased NDV replication in the brain is associated with a higher IPCI score, suggesting that viral replication in the brain is an intrinsic feature of the very virulent strains. This study is the first description of NDV pathology of chickens infected with the ICPI method, and offers a useful roadmap to better understand the biological meaning of the ICPI, and to serve in future detailed NDV neuropathogenesis studies.