A new study finds no difference in the racing career longevity between horses who experience some level of exercise-induced pulmonary hemorrhage and those who never experience EIPH.
The retrospective descriptive study of clinical endoscopy, EIPH status, and racing records, examined 822 geldings who were imported to Hong Kong and raced there between 2007 and 2012. The study, which was previewed late last year in The Blood-Horse, was accepted this month for publication by the Equine Veterinary Journal.
Study author Stephanie Preston, of the Maxwell H. Gluck Equine Research Center's Equine Soundness and Sports Medicine Program at the University of Kentucky, said her study indicates low level EIPH is common but does not impact performance or the horse's ability to stay in training.
"Maybe bleeding is a consequence of vigorous exercise but not necessarily a problem," Preston said late last year as she was finalizing the study. "The data suggest this is not a long-term issue for performance."
The study, "Descriptive Analysis of Longitudinal Endoscopy for Exercise Induced Pulmonary Hemorrhage in Thoroughbred Racehorses Training and Racing at the Hong Kong Jockey Club," was funded by the Equine Soundness Program, a collaboration of the University of Florida's College of Veterinary Science, Department of Large Animal Clinical Services; and the Gluck Equine Research Center.
Through use of an endoscope, EIPH incidents are graded on a five-point scale, with grade 0 representing no blood in the pharynx, larynx, trachea, or mainstem bronchi; on up to grade IV, which would be full epistaxis (visible bleeding from the nostrils).
Grade I bleeding would be a few small specks on the airway walls and grade II EIPH would be a long stream of blood more than half the length of the trachea, or two shorter streams occupying a third of the tracheal circumference. Grade III EIPH would be multiple distinct streams of blood covering more than a third of tracheal circumference while grade IV, full epistaxis (visible bleeding through the nose), would include blood covering the tracheal surface and possibly present in the larynx pooling at the thoracic inlet.
Preston found Hong Kong, where race-day Salix (furosemide, and also commonly called Lasix) is prohibited, to be an excellent circuit to conduct her study. Horses there are housed in a similar environment, under similar circumstances, and train and race on the same surfaces.
Trainers can request endoscopic examinations at any time and such information is monitored closely by racing regulators. Horses with endoscopic exams that show EIPH of grade III levels or epistaxis, are subject to close monitoring and must breeze without registering EIPH higher than grade II. Preston had access to this data collected by Hong Kong Jockey Club.
Preston's study found that of the 822 horses examined, 732 received at least one endoscopy and 724 received two or more exams. Of that group, 55% (405) showed some level of EIPH, while 45% did not bleed at all. The most severe form of EIPH, epistaxis, was seen in just 4% of the horses.
The study found no statistically significant difference in number of starts for EIPH-positive horses when compared with EIPH-negative horses. In fact, the EIPH-positive group raced in slightly more races, but not to the point of being statistically relevant.
"The results indicate that the diagnosis of EIPH does not impact the length of career of Thoroughbreds racing in Hong Kong or the total number of starts a horse makes during its career," the paper reads.
The small percentage of horses who did experience epistaxis stayed in training for 699 days. That was shorter than horses who experienced lower grades of EIPH. The low-level EIPH-positive group stayed in training an average of 842 days from import to Hong Kong until retirement.
The study determined that of the group that showed some level of EIPH, the median number of times they were diagnosed with any level of EIPH was just three during a median number of 18 lifetime races.
The study also concluded that horses diagnosed with higher grades of EIPH are more likely to register higher grades of EIPH in the future. Not surprisingly, horses who experience epistaxis are more likely to be retired for EIPH-related conditions than other EIPH-positive horses.
Preston also spent more than 25 years in racing as an exercise rider, rider, trainer, and farm manager, and at the time favored the U.S. policy of allowing Salix as a treatment of EIPH. She has changed her mind and hopes her new study provides a fact-based foundation for further debate.
"For 25 years I believed Lasix was a very necessary medication," Preston said. "Because we allow it, we think we need it."