Experimental atrophic rhinitis in gnotobiotic pigs.

Twenty-nine caesarian derived colostrum deprived germfree pigs were reared in isolators in groups of three to four per isolator. At seven days of age each group was inoculated intranasally with one of four strains of Bordetella bronchiseptica (designated B, J, L and 55B), or Pseudomonas aeruginosa or a mucoid strain of Escherichia coli, all previously isolated from nasal mucus of pigs affected with clinical atrophic rhinitis. Another group was inoculated simultaneously with B. bronchiseptica B and Pasteurella multocida. The animals were observed for clinical signs of atrophic rhinitis and monitored bacteriologically at weekly intervals for seven weeks. Then they were bled for serology and killed and their respiratory organs examined for gross and histopathological lesions. All of the pigs inoculated with the Bordetellae had inflammation of the nasal mucosa and developed positive serum antibody titers against all four of the Bordetella strains used in this study. Strain J caused sneezing and turbinate atrophy in three of four pigs. One of the three pigs inoculated with strain L died in ten days from bronchopneumonia and pericarditis and had turbinate atrophy. Strains B and B55 caused no turbinate atrophy, but two out of three pigs inoculated with both B. bronchiseptica B and P. multocida had turbinate atrophy. No nasal lesions were observed in the pigs inoculated with E. coli or P. aeruginosa or in the noninoculated germfree controls. The results indicate a variation in the ability of different strains of B. bronchiseptica to cause turbinate atrophy in pigs and demonstrate that nasal infections by these organisms stimulate serum antibody response. Presence of P. multocida appears to increase the severity of the lesions. As the E. coli and Pseudomonas failed to produce atrophic rhinitis, they are probably of no significance as primary etiological agents in the atrophic rhinitis syndrome in swine.