Athletic Performance of Horses Previously Infected with R. equi Pneumonia as Foals

Rhodococcus equi infection produces an insidious disease in foals 1 to 4 months of age, with intrapulmonary and extrapulmonary abscessation and organ dysfunction as common sequelae. Although amenable to treatment, this foalhood pneumonia has an impact on later athletic performance that has remained controversial. Christley and Hodgson1 noted that <64% of their recovered hospital cases (n 5 11) raced at least once, whereas Lavoie et al.2 reported that only 23% of the R. equi affected foals survived and raced successfully. In both studies, earnings or performance records of cases were not detailed. In contrast, Bernard et al.3 found no significant difference in the average earnings between the R. equi affected horses and controls (siblings) or between the R. equi affected horses and the average earnings of North American cohorts. However, although this study and those cited earlier established that some recovered foals can successfully race, it remained unknown if the severity of the bacterial infection impacted negatively upon race performance. Thus a multicenter retrospective study was conducted to determine if physical examination parameters, laboratory data, or radiographic abnormalities were associated with (a) reduced survival; (b) a reduced ability to race at least once; or (c) reduced earnings or starts.