Frequency of and risk factors for epistaxis associated with exercise-induced pulmonary hemorrhage in horses: 251,609 race starts (1992-1997)

Objective - To determine the frequency of epistaxis during or after racing among racehorses and identify factors associated with development of epista xis. Design - Retrospective study. Sample Population - 247,564 Thoroughbred and 4,045 Angle-Arab race starts. Procedure - Race start information (breed, age, sex, racing distance, and r ace type) was obtained for Thoroughbred and Angle-Arab horses racing in Jap an Racing Association-sanctioned races between 1992 and 1997. All horses th at raced were examined by a veterinarian within 30 minutes of the conclusio n of the race; any horse that had blood at the nostrils was examined with a n endoscope. IS blood was observed in the trachea, epistaxis related to exe rcise-induced pulmonary hemorrhage (EIPH) was diagnosed. Results - Epistaxis related to EIPH was identified following 369 race start s (0.15%). Frequency of EIPH-related epistaxis was significantly associated with race type, age, distance, and sex. Epistaxis was more common followin g steeplechase races than following flat races, in older horses than in hor ses that were 2 years old, following races less than or equal to 1,600 m lo ng than following races between 1,601 and 2,000 m long, and in females than in sexually intact males. For horses that had an episode of epistaxis, the recurrence rate was 4.64%. Conclusions and Clinical Relevance - Results suggested that frequency of EI PH-related epistaxis in racehorses is associated with the horse's age and s ex, the type of race, and the distance raced. The higher frequency in short er races suggests that higher intensity exercise of shorter duration may in crease the probability of E[PH.