Effect of erythromycin and colistin ophthalmic ointment on post‐race keratitis in Thoroughbred racehorses

BACKGROUND: This study investigated the prophylactic efficacy of administering an ophthalmic ointment containing erythromycin and colistin (EC ointment) after racing to prevent post-race keratitis in Thoroughbred racehorses. METHODS: The incidence of post-race keratitis following turf and dirt races was compared between treatment groups (non-ointment group: eye flushing only; ointment group: eye flushing and application of EC ointment) and between two randomly assigned groups (non-antimicrobial group: application of ophthalmic white petrolatum; antimicrobial group: application of EC ointment). RESULTS: After turf races, the incidence of post-race keratitis was significantly higher in the non-ointment group (6.25%; 63/1008) than in the ointment group (0.55%; 53/9659) and in the non-antimicrobial group (8.18%; 13/159) than in the antimicrobial group (0%; 0/152). In contrast, after dirt races, no significant differences were found between the non-ointment (0.56%; 8/1420) and ointment (0.53%; 53/9986) groups, or between the non-antimicrobial (1.87%; 4/214) and antimicrobial (1.41%; 3/213) groups. LIMITATIONS: Microbiological and cytological testing was limited, and the pathogenesis of post-race keratitis remains unclear. CONCLUSIONS: EC ointment effectively reduced the incidence of post-race keratitis after turf races, but not after dirt races. Although the findings suggest bacterial involvement in the pathogenesis of post-turf-race keratitis, further microbiological and cytological testing is warranted to confirm this.