Exercise-induced pulmonary hemorrhage in Thoroughbreds after racing and breezing.

This study investigates the prevalence of exercise-induced pulmonary hemorrhage (EIPH) in racehorses after participating in different types of races and training exercises. The findings present a significant incidence of EIPH and indicate that the occurrence of this condition relies heavily on the horse’s age and the distance they race or train, with no significant relation to their sex or race outcome.

Study Design and Participants

• The study involved thoroughbred horses that were examined after participating in racing or breezing (a milder form of exercise).
• A total of 191 horses were examined after racing on a dirt track, and 107 horses were examined after breezing.
• Additional thoroughbred horses were also studied after steeplechase, flat turf, and timber races.

Method of Examination

• All horses were examined within two hours of their respective activities using a flexible fiberoptic endoscope. This is a technique used to visualize the internal structures of the body, in this case, the respiratory system, to detect any signs of EIPH.
• The main symptom of EIPH, bleeding from the nostrils, was also closely observed.

Findings

• A significant number of the horses exhibited signs of EIPH, with 75.4% of the racers and 38.3% of the horses that had been breezing showing evidence of this condition. Blood at the nostrils, a clear indication of EIPH, was observed in 9.0% of the EIPH positive racers and 2.4% of the breezing horses.
• After the steeplechase, flat turf, and timber races, 67.7%, 14.3%, and 66.6% of the horses respectively were EIPH-positive. The percentage of these EIPH-positive horses that had blood at the nostrils was 14.3%, 0%, and 100%, respectively.
• In a third survey involving 32 breezing Thoroughbreds, 65.5% were found to be EIPH-positive. None of these horses exhibited blood from the nostrils.
• Statistical analysis showed a relationship existed between the incidence of EIPH and factors such as the horse’s age or distance they raced or breezed. However, no significant relationship was found between EIPH and sex or race outcome.
• The study also notes that endoscopic findings of EIPH are repeatable in horses, signifying that EIPH occurrence is not a random event but may be related to specific triggers or predisposing factors.