Ulcerative keratitis in thoroughbred racehorses in Japan from 1997 to 2008

To describe the number of cases, etiologies, healing times, and results of microbial culture and susceptibility testing of corneal ulcers in thoroughbred racehorses in Japan.

Retrospective study of the medical records of racehorses belonging to the Japan Racing Association (JRA) from 1997 to 2008.

A total of 2846 horses suffered ulcerative keratitis. These horses accounted for 90.5% of all the corneal problems and 54.9% of the entire number of horses with ocular diseases. Running in races was the cause in 64.3% of the cases. The mean healing time of the ulcers developed in races was 5.5 + or - 9.6 days, which was shorter than that of the ulcers unrelated to racing (8.6 + or - 11.7 days). In horses presented for examination by the next day after the race, healing was even more rapid (4.1 + or - 7.5 days) than in horses presented later (12.4 + or - 14.7 days). Microbial culture was performed on 74 samples of 58 horses. Forty-four bacterial and four fungal organisms were isolated from 35 samples of 29 horses. Pseudomonas aeruginosa (10) and Streptococcus equi subspecies zooepidemicus (5) were the bacteria most frequently isolated. There was no tendency of increasing antibiotic resistance of these organisms.

Ulcerative keratitis is the most frequent corneal and ocular disease of the racehorse in Japan. Careful observation of the eyes after racing is necessary as early diagnosis and treatment of corneal ulcers speeds healing. Many antibiotic have efficacy against the bacterial isolates, however, potent antibiotics should be reserved for the most severe corneal ulcers.