Structural changes associated with type-A influenza in Mallard duck tracheal organ culture

Mallard duck tracheal organ cultures were used to study structural changes associated with infection with type-A influenza (A/Turkey/WIS/68) (H9N2) at the light-microscope and electron-microscope levels. Light-microscope changes in infected organ culture were cytoplasmic vacuolization, nuclear swelling, reduction in ciliated epithelium, and sloughing of epithelial cells. Ultrastructural changes included the loss of cilia and microvilli, distortion and swelling of cellular organelles, breakdown of intercellular junction, and apparent phagocytosis of the ciliated epithelium. Numerous budding virions were noted at the plasmalemma. Virus was detected by egg inoculation from all experimental cultures throughout the 192-hour experiment.