LACK OF RESIDUAL LUNG DAMAGE IN HORSES IN WHICH RHODOCOCCUS EQUI-INDUCED PNEUMONIA HAD BEEN DIAGNOSED

The effect of prior Rhodococcus equi-induced pneumonia on pulmonary he alth was investigated in 5 horses (<24 months old) using endoscopy, ra diography, hematologic and bronchoalveolar lavage analyses, and pulmon ary function testing. Rhodococcus equi-induced pnuemonia had been diag nosed in principal horses when they were foals. Diagnosis was based on positive results of transtracheal aspiration and thoracic radiography at the time of initial clinical examination. Results of reevalution o f the respiratory system of these horses (R+) were compared with those of 5 age-matched healthy horses (R-) that lacked clinical or historic al evidence of foalhood pneumonia. Significant differences in variable s between the 2 groups of horses were not evident. In both groups, mos t horses had radiographic evidence of an accentuated bronchointerstiti al pattern, although results of analysis of bronchoalveolar lavage spe cimens were normal and mononuclear cells predominated. Variability in results of the pulmonary function tests was observed within and betwee n the 2 groups of horses. Only normalized dynamic lung compliance was slightly lower in the previously infected horses, but this difference was not significant. We concluded that horses previously infected with and successfully treated for R equi-induced pneumonia do not have det ectable evidence of residual lung damage.