1a.Objectives (from AD-416):
The objective is to characterize and compare the pathology of different Newcastle disease viruses from other part of the world to define NDV virulence mechanisms.
1b.Approach (from AD-416):
Pathogenesis studies will be conducted in SEPRL SPF leghorn chickens
to characterize the clinical form of any resultant disease and tissue tropism of the infection. Domestic and exotic field isolates as well as newly generated recombinant vaccine viruses will be tested. In brief the protocol is to inoculate 4-wk-old chickens by eye drop, a natural route of infection in contrast to pathogenicity testing done by systemic inoculation. Clinical observations will be recorded over a 14 day period and 2 birds will be euthanized for sampling at 2, 5, 10, and 14 days post inoculation. Birds dying from infection will be included in sampling. Tissues will be collected into 10% formalin for processing, sectioning and staining for histopathology, in situ hybridization (ISH) with a NDV matrix gene riboprobe to detect NDV mRNA, and immunohistochemistry (IHC) with an NDV anti-peptide serum to detect expressed NDV nucleoprotein (N). Other riboprobes may also be used. Seroconversion detected in blood samples collected on days 10 and 14 and/or virus isolated from oral and cloacal swabs collected at each sampling will confirm infection in sampled birds that display no clinical signs of disease. Selected tissues may also be processed separately for virus isolation or for RNA isolation. Infections of other birds species may also be evaluated similarly if there appears to be a host predilection for some isolates. New plasmids for creation of recombinant viruses will be developed.
This research is directly related to inhouse objective 1.A - Determine the impact of variant and emerging viruses on the evolution and control of Newcastle disease by determining the presence of variant and emerging Newcastle disease viruses in wild birds and live poultry markets.
One pathogenesis experiment has been conducted and characterization of paraffin embedded samples from virulent Newcastle disease virus from Belize has been done. The Belize viruses have been determined to be viscerotropic velogenic Newcastle disease viruses. One publication is in preparation.