Transverse sections of snouts from 171 cross-bred (principally Yorkshire X American Landrace) pigs were evaluated for evidence of turbinate atrophy by use of conventional (atrophic rhinitis [AR] score) and morphometric methods. Of the 171 pigs, 35 were clinically normal (AR score, 0), 65 had mild AR (AR score, 1), 41 had moderate AR (AR score, 2), and 30 had severe AR (AR score, 3). Turbinate cross-sectional area (TA) and the ratio of TA to nostril cross-sectional area, called turbinate area ratio (TAR), had the lowest correlations (r = 0.24 to 0.55) with conventional AR score. Among clinically normal pigs, TA was greater in older pigs as expected, but the TAR values also were significantly (P less than 0.0001) different betwee n 15-week-old pigs (55 kg) and 22-week-old pigs (100 kg). Turbinate perimeter and turbinate perimeter ratio (TPR) were not influenced by pig age or source. The TPR values were closely correlated with subjective visual AR scores (r = 0.73), with AR scores derived by measuring the space between the ventral portion of the scroll and the floor of the nasal cavity (r = 0.72), and the actual size of this space in millimeters (r = 0.71). Mean TPR values for pigs assigned visual AR scores of 0, 1, 2, or 3 were 1.54, 1.25, 0.97, and 0.73, respectively. The 95% confidence intervals around these mean TRP values were discreet and did not overlap. Turbinate perimeter ratio, therefore, may be a more reliable morphometric measure of atrophic rhinitis and also provides parametric data suitable for quantitative analysis.

Eight healthy nonstressed calves were inoculated with Pasteurella haemolytica serotype 1, by instilling a broth culture into the middle nasal meatus of the left nostril. The inoculated left nostrils shed P haemolytica from the ventral nasal meatus at a steady rate for a mean of 7 days, whereas the uninoculated right nostrils of the same calves shed P haemolytica sporadically and in lower concentrations. The duration, frequency, and concentration of P haemolytica shed from the inoculated nostrils was significantly (P less than 0.05) greater than from the nostrils of other healthy calves that had been exposed by instilling the culture into the ventral nasal meatus of both nostrils in a previous study. The concentration of antibodies (IgG, IgA, and IgM) to P haemolytica increased significantly (P less than 0.05) in serum and nasal secretions after exposure. Four weeks after initial P haemolytica exposure, calves were exposed to infectious bovine rhinotracheitis virus and became clinically ill. Four calves were induced to shed P haemolytica from both nostrils by the virus infection; thus, they were harboring the bacterium and were susceptible to active recolonization. Four calves were not induced to shed P haemolytica. The apparent reason was not that they were resistant to active colonization, but that they were no longer harboring the bacterium, because they became active shedders after they were reinfected with P haemolytica.

Experimental intranasal inoculation of cattle with Pasteurella haemolytica serotype 1 resulted in a group that shed the bacteria in their nasal secretions (colonized) and a group that did not shed (uncolonized). After inoculation, antibody titers in serum and nasal secretions against the total P haemolytica increased significantly, and the proportion of total antibody against specific P haemolytica antigens changed so that the proportion directed against the 94- and 62-kD antigens increased. Prior to inoculation, the proportion of total antibody in the serum against 94- and 62-kD antigens of P haemolytica was higher in calves that remained uncolonized than in those that became colonized with P haemolytica after exposure. Antibody specificity of serum and nasal secretions differed in the relative amounts directed against each P haemolytica antigen. The specificity against P haemolytica antigens differed between IgG and IgA isotypes of serum and nasal secretions, with IgA being directed against fewer antigens than was IgG.