Quantitative observations on Bordetella bronchiseptica infection in atrophic rhinitis of pigs

Clinical atrophic rhinitis in seven pig herds could not be associated with the infection rate or higher numbers of B bronchiseptica in nasal swabs when compared with unaffected herds. B bronchiseptica isolates from herds with atrophic rhinitis and receiving sulphonamide medication were resistant to sulphonamides in vitro and there was a beneficial clinical response after changing to oxytetracycline medication. In an unaffected herd three piglets naturally infected with B bronchiseptica but possessing low levels of passive antibody showed marked turbinate hypoplasia when killed at seven weeks, the lesions had resolved in four of six litter mates by 21 weeks and did not occur in another litter of nine piglets which had a high level of passive antibody. The results indicate that although B bronchiseptica can produce non-progressive turbinate changes in pigs that have inadequate antibody protection, the relationship between these lesions and the chronic progressive field disease needs further investigation.