Lung lesions were found in mycoplasma infected calves using either route of inoculation.

<p>Histopathological findings in the lungs of control calves (<i>N</i> = 8) or calves inoculated with <i>M. bovis</i> by oral (<i>N</i> = 8) or transtracheal (<i>N</i> = 5) routes. Samples were collected at necropsy (14 days post-infection, except for one calf inoculated with <i>M. bovis</i> by the oral route which had to be euthanized at 10 days post-infection). a) Overall histopathological lesion scores. b) Subscores for lymphoid hyperplasia. Data are represented as scores for individual calves with the median value indicated by a horizontal line. Tissues were graded on a subjective scale from 1 (minimal or no lesions) to 5 (most severe lesions) and from 1 (no lymphoid hyperplasia) to 4 (marked lymphoid hyperplasia) for lesion scores and lymphoid hyperplasia subscores, respectively. ^abSuperscript letters indicate significant (<i>P</i><0.05) differences between groups. c) Representative histopathologic appearance of a lung section with a lesion score of 1 (control calf). Magnification ×10. d) Representative histopathologic appearance of a lung section with a lesion score of 5 (orally-inoculated calf from which <i>M. bovis</i> was recovered from the lung). Magnification ×10.