Changes in the nasal mucosa of specific-pathogen-free neonatal pigs infected with Pasteurella multocida or Bordetella bronchiseptica.

Abstract

Specific-pathogen-free neonatal pigs were intranasally inoculated with serotype D strains of Pasteurella multocida or with strain L3 of Bordetella bronchiseptica, and changes in the nasal mucosae were examined with a scanning electron microscope (SEM) or a light microscope. P. multocida caused slight chronic catarrhal inflammatory changes in the infected nasal mucosa, but most of the epithelial cells appeared intact. A small number of lymphocytes and neutrophils infiltrated the lamina propria and submucosa, and a small amount of a mucopurulent substance accumulated on the mucosa. P. multocida was not readily observed on the nasal mucosa by SEM, though a low number of the organisms were constantly recovered from the nasal cavities of the infected pigs throughout the experimental period. In contrast, marked inflammatory changes were observed after the infection by B. bronchiseptica. Degeneration and desquamation of the nasal epithelial cells were noted throughout the infected nasal mucosa. Cilia were lost from most of the ciliated epithelial cells. Marked hyperplasia of the epithelial cells was also observed in many parts of the epithelium. B. bronchiseptica was frequently noted on the remaining cilia or on the microvillous cells by SEM, and numerous organisms were constantly recovered from the nasal cavities of the infected pigs during the period. Clinical atrophic rhinitis was induced only in the pigs given B. bronchiseptica.