Foal-related risk factors associated with development of Rhodococcus equi pneumonia on farms with endemic infection

Objective-To identify foal-related risk factors associated with development of Rhodococcus equi pneumonia among foals on farms with endemic R equi infection. Design-Prospective case-control study. Animals-220 foals at 2 equine breeding farms in Texas during a 2-year period. Procedure-Information collected for each dam included age, time housed on the farm prior to parturition, whether there were any peripartum illnesses, parity, and health of previous foals. Information collected for each foal included breed, sex, gestational age, month and year of birth, location of birth, type of flooring and bedding in stall, postpartum management and preventive health care, passive immunity status, supplementation of immunoglobulins, expo sure to other farms or foals affected with R equi pneumonia, stall and pasture exposure, commingling with other mare-foal pairs, age at weaning, and whether the foal developed R equi pneumonia. Results-32 of the 220 (15%) foals developed R equi pneumonia, of which 4 (13%) died. Foals at 1 of the 2 farms and foals born during the second year of the study were more likely to develop R equi pneumonia. Foal-related factors that were examined were not significantly associated with risk of R equi pneumonia in multivariate analyses. Conclusions and Clinical Relevance-Results suggest that there are farm- and year-related effects on the risk that foals will develop R equi pneumonia. Other foal-related factors significantly associated with R equi pneumonia were not identified.