Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/1995
Publication Date: N/A
Interpretive Summary: Chicken inoculation is the standard method to determine the ability of Newcastle disease virus (NDV) to produce disease (pathogenicity). Any factor that can influence the outcome of the chicken inoculation test can thereby affect the pathogenicity characterization of a culture, the assessment of the potential hazard of that NDV culture to poultry, and the e initiation of the appropriate control program to prevent spread of the infection. The results of this study demonstrated that white leghorns, a breed used primarily for egg production, had more severe clinical disease and higher mortality rates from NDV infection than similarly inoculated white rocks, a heavy breed used primarily for meat production. The differences in the results between the two breeds was not enough to change the pathogenicity classification of the tested isolates, but the results from leghorns more clearly identified the hazard of those isolates for poultry. The extent of variation of Newcastle disease resistance among breeds or lines of chickens used for testing at other laboratories is unknown. Variation in results among laboratories, regardless of the source, makes interlaboratory comparisons of results difficult.
Technical Abstract: Three isolates of Newcastle disease virus (NDV) from cormorants and turkeys were classified as velogenic neurotropic NDV (VNNDV) by standard pathotyping procedures in specific-pathogen-free white leghorn and white rock chickens. White leghorns inoculated by eye drop, cloaca, intravenous, or intracerebral routes had a higher frequency of nervous signs and mortality than was observed in similarly inoculated white rocks Two backpassages in white rocks increased the intravenous pathogenicity index of all three isolates, but none had a value after backpassage that was as high as the classical VNNDV strain Texas-GB. The breed of chicken used in standard procedures did influence the results of pathotyping determinations, but the differences between breeds were not large enough to change the pathotype assigned to these isolates.