Development of turbinate lesions and nasal colonization by Bordetella bronchiseptica and Pasteurella multocida during long-term exposure of healthy pigs to pigs affected by atrophic rhinitis.

Natural transmission of atrophic rhinitis from pigs from a herd with an endemic atrophic rhinitis problem to pigs from a herd free of atrophic rhinitis was demonstrated. Six replicates each with five pigs from the endemic atrophic rhinitis herd (Group A) and five pigs from the atrophic rhinitis-free herd (Group B) were housed together from 5 wk of age, with each replicate kept in isolation rooms maintained at optimal and controlled environmental conditions. Three replicates each with six pigs/room from the atrophic rhinitis-free herd (Group C), served as nonexposed controls. Group C pigs remained healthy and had no turbinate atrophy at either 10 or 17 wk of study (atrophic rhinitis score = 0 on a 0 to 3 scale). Group A pigs had a mean atrophic rhinitis score of 1.85 +/- 0.84, and group B pigs developed atrophic rhinitis to a mean score of 1.57 +/- 0.70. The isolation rate and quantity of Pasteurella multocida found on nasal swabs was directly related to lesions while those for Bordetella bronchiseptica were inversely related to turbinate atrophy. Of the various types of P. multocida evaluated, nontoxigenic type A and toxigenic type D were both directly related to atrophic rhinitis while nontoxigenic type D strains were not. No toxigenic type A P. multocida strains were isolated.