Pathogenesis of Newcastle Disease in Chickens Experimentally Infected with Viruses of Different Virulence

Abstract

Abstract. Groups of 4-week-old White Rock chickens were inoculated intraconjunctivally with nine isolates of Newcastle disease virus representing all pathotypes. Birds were monitored clinically and euthanatized sequentially, with collection of tissues for histopathologic examination and in situ hybridization using an antisense digoxigenin-labeled riboprobe corresponding to the sequence of the gene coding for the matrix protein.Disease was most severe with velogenic viscerotropic pathotypes and was characterized by acute systemic illness with extensive necrosis of lymphoid areas in the spleen and intestine. Viral nucleic acid was detected in multiple tissues but most prominently in macrophages associated with lymphoid tissue. Velogenic neurotropic isolates caused central nervous system disease despite minimal amounts of viral nucleic acid detected in neural tissue. Mesogenic and lentogenic pathotypes caused no overt disease; however, viral nucleic acid was present in myocardium and air sac epithelium following infection with these isolates. Compromise of air sac and myocardium may predispose mesogen-and lentogen-infected chickens to secondary infection and/or decreased meat and egg production.

The VG/GA strain of Newcastle disease virus: mucosal immunity, protection against lethal challenge and molecular analysis

“…The replication pattern of VG/GA strain induced a stronger localized mucosal immune response in the intestinal tract shown by an increased production of NDV-specific IgA. This feature may represent a competitive advantage in the event of a velogenic viscerotropic challenge where the virus has been reported to induce massive destruction of intestinal lymphoid areas and extensive ulceration of overlying intestinal epithelium associated with active viral replication (Brown et al, 1999).…”

“…Antibody production in the mucosa is closely related to viral replication in the target cells, hence the pathogenesis and tissue tropism of the viruses used for vaccination is to be considered in order to assess the efficacy of a given live vaccine against a direct challenge (Jayawardane & Spradbrow, 1995). The intestinal tropism of the VG/GA strain and the consequent induction of local immunity may be important for protection against velogenic-viscerotropic strains of NDV that have been reported to induce massive destruction of intestinal lymphoid areas and extensive ulceration of overlying intestinal epithelium (Brown et al, 1999).…”

Determination of the distribution of lentogenic vaccine and virulent Newcastle disease virus antigen in the oviduct of SPF and commercial hen using immunohistochemistry

“…Positive labeling was noted either intracellularly or extracellularly (not clearly cell-associated) in the oviduct. Per section, one ''hot spot'' was identified (defined as the field with the greatest amount of immunolabeling) and within the ''hot spot'', cells were counted and grading was performed according to Brown et al (1999) as follows (Table 1b):…”

Changes in fat metabolism of black-bone chickens during early stages of infection with Newcastle disease virus

“…ND is considered an acute and infectious disease, with plenty of previous research indicating effects of NDV on animal physiology (Brown et al, 1999). This study attempted to specifically pinpoint changes in the fat metabolism of chickens infected with the NDV.…”