الفهرس 
Strain classification, Antigenicity and Pathogenicity of NDVOnly 14 pages are availabe for public view
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Abstract
The chicken and duck are important hosts of Newcastle disease virus (NDV)
with distinctive responses to infection. NDV infection in ducks is often subclinical
and chronic, while in chickens the infection is clinically apparent and transient.
These differences may be due to in part to the host response to NDV infection.
Lentogenic NDVs, circulating among waterfowl, have the potential to become
highly pathogenic by replication in chickens. The pathological studies which
compare between NDV infections in chickens and waterfowl are rare. The virulent
9a5b mutant NDV isolate was generated by passaging the lentogenic
Goose/Alaska/415/91 NDV isolate in chickens. The pathogenesis of the 9a5b
isolate is unknown in both chickens and waterfowl. In this study, the virulent 9a5b
mutant NDV isolate was inoculated intranasally in 32-day-old specific pathogenfree
white Leghorn chickens and Japanese commercial ducks. This study compares
the histopathological alterations in chickens and ducks following 9a5b NDV
infection. Haematoxylin and eosin (HE) stain was used to investigate the tissue’s
histological alterations. NDV nucleoprotein (NDV-NP), glial fibrillary acidic
protein (GFAP) and interferon (IFN)-β were detected by immunohistochemistry
(IHC), apoptosis was detected by HE staining, caspase-3 IHC and the TUNEL
assay. Apoptosis in buffy coat layer was detected by toluidine blue stained semithin
section and confirmed by agarose gel electrophoresis. Unlike ducks, which
remained clinically normal throughout the study, chickens were shown depression,
gasping, oral discharges and greenish white soft feces. Gross and histologic lesion
patterns as well as viral replication supported the differing clinical outcome. In
immune organs, labelling of NDV-NP and lymphoid depletion were most marked
in chicken. The pattern of apoptosis in the spleen differed between chickens and
ducks. In chickens there were numerous apoptotic cells in the peri-ellipsoidal
white pulp, the peri-ellipsoidal, peri-arteriolar and peri-venous lymphoid sheaths,
while apoptosis in duck spleens was mainly within the germinal centers. Lymphoid
depletion was the main feature in the bursal and thymic tissues of chickens, but
apoptosis was marked in these organs in ducks. Ducks had slight inflammation
mainly in respiratory and digestive tracts, whereas slight nonpurulent encephalitis,
necrotizing pancreatitis, tubulointerstitial nephritis, and mild inflammation in
respiratory and digestive tracts were detected in chickens. Expression of IFN-β
appeared earlier and was more intense in the tissues from ducks compared with
those from chickens. The differences in IFN-β and NDV-NP expression may
reflect the relative clinical severity of the infection in the two avian species.