Airborne-induced experimental Bordetella bronchiseptica pneumonia in Strain 13 guineapigs

Summary To evaluate the efficacy of a commercial bacterial vaccine in protecting Strain 13 guineapigs against fatal Bordetella bronchi- septica pneumonia, it was necessary to establish the infectivity and disease pathogenesis induced by virulent organisms. When guinea pigs were exposed to small-particle aerosols of varying concentrations of virulent B. bronchiseptica, a spectrum of disease was produced that ranged from inapparent illness to fulminant broncho- pneumonia. Clinical signs began by day 4 after exposure, and were evidenced by anorexia, weight loss, respiratory distress and serous to purulent nasal discharge. Pathological altera- tions were limited to the respiratory system. Moribund animals exhibited a suppurative necrotizing bronchopneumonia and necrotizing tracheitis. In animals that survived the chal- lenge, the bacteria were eliminated from the lungs by day 28 but continued to persist in the laryngeal area and the trachea. The median infectious dose and the median lethal dose were estimated to be 4 colony-forming units (CFU) and 1314 CFU respectively. These data suggest that the guineapig will be a valuable model system in which to study interactions between Bordetella species and host cells as well as to evaluate potential B. bronchiseptica immunogens.