Abstract
Ultrastructural changes in the tracheal epithelium of chickens infected intranasally with velogenic viscerotropic Newcastle disease virus were examined by scanning EM. Hypertrophy of the mucus-secreting, or goblet, cells was the first sign of change, followed by disoriented and deformed cilia, hemorrhage and hyperplasia of goblet cells accompanied by an increase in mucus. By day 7 postinfection, there was a marked decrease in the number of ciliated cells. Submucosal glands and some collagen fibers were exposed to the surface, an indication of loss of the epithelial cells. Macrophages and cell debris were abundant; hyperplasia of the basal cells was evident in the later stages of infection, probably in an attempt to regenerate the lost epithelium. All chickens died 10 days postinfection before any further work could be done.