Pathology of trachea in turkeys exposed by aerosol to Newcastle disease virus
This study was undertaken to characterize tracheal lesions and to determine tracheal virus titers in turkeys exposed by aerosol to lentogenic, mesogenic, and velogenic strains of Newcastle disease virus (NDV). Three experiments were done; the purpose of the first experiment was to compare tracheal lesions and virus titers following aerosol exposure to different lentogenic strains of NDV. The second and third experiments were designed to compare the progression of tracheal lesions and the pattern of tracheal virus titers following aerosol exposure to lentogenic, mesogenic, or velogenic strains of NDV;In the first experiment, five groups of 4-week-old turkeys were each exposed by aerosol to a different lentogenic strain of NDV (cloned LaSota, uncloned LaSota, Bl, ET, and 2024). Four days postexposure (PE), tracheas were collected for histopathologic characterization and virus titration. All strains multiplied to high titers and produced similar microscopic lesions characterized by fibrinopurulent exudation, epithelial cell hyperplasia, and lymphocytic infiltration;In the second experiment, 5-week-old turkeys were exposed by aerosol to the LaSota strain of NDV. In the third experiment, 5-week-old turkeys were exposed by aerosol to the Roakin or GB strain of NDV. In both experiments, tracheas were collected at 2-14 different days PE and processed for histologic examination and virus titration. Two days PE, swelling of epithelial cells occurred in tracheas infected with the LaSota or Roakin strain, whereas there were loss of ciliated cells and epithelial cell hyperplasia in tracheas infected with the GB strain. With all three strains, epithelial cell hyperplasia was a consistent feature on day 4. Differentiated epithelium appeared in the mucosa on day 10 with the LaSota strain and on day 6 with the Roakin or GB strain. Regardless of the strain, NDV was isolated from all tracheas collected 2, 4, and 6 days PE. All strains achieved high virus titers on day 2; however, virus titers on days 4 and 6 were higher in tracheas infected with the LaSota strain than in those infected with the Roakin or GB strain.