AAEP Convention 2005: Exercise Induced Pulmonary Hemorrhage

Exercise-induced pulmonary hemorrhage (EIPH), or bleeding in the lungs after exercise, costs the United States horse racing industry a great deal--estimated at up to $260 million per year by Kenneth W. Hinchcliff, BVSc, MS, PhD, Dipl. ACVIM, of The Ohio State University. During his presentation at the American Association of Equine Practitioners Convention, held Dec. 3-7 in Seattle, Wash., he discussed the prevalence of the disease and its economic and performance effects on U.S. Thoroughbred and Standardbred racehorses.

"Exercise-induced pulmonary hemorrhage is ubiquitous among Thoroughbred racehorses throughout the world, and there is no apparent important geographic variation in incidence of the condition," he noted.

One study examining Thoroughbreds via endoscopy after a single race found that 55% exhibited EIPH to some degree, he reported. After following the horses for three races, 85% bled after at least one race. Standardbred racehorses showed a prevalence rate of 87% after at least one of three races. Using examination of bronchoalveolar lavage (BAL; "washing" of a part of the lung with fluid and collecting the fluid for analysis) fluid, one study found that almost all Thoroughbreds racing or in race training examined had evidence of EIPH (more on diagnosis in a moment).

"The risk factors for EIPH are not well defined," Hinchcliff said. "Suggested factors include age, distance, speed, track surface, and environmental conditions."

Hinchcliff spent a bit of time discussing the economic impact of this common disease, which he noted is not well defined and does not include less tangible costs such as impaired performance, missed races, lost training days, or shortened careers. "This is quite difficult to calculate," he said.

He reported that there were about 250,000 Thoroughbreds and Standardbreds in race training in the United States in 2003, with 444,586 Thoroughbred starts and 635,292 Standardbred starts. He estimated the costs of detection and treatment (excluding furosemide, or Salix) at $450-$900 per horse per year. Furosemide costs nearly another $36 million annually for the 90% of Thoroughbreds and 50-70% of Standardbreds that race on it, he added. The total impact of EIPH on the U.S. racing industry he estimated at $135-$260 million annually.

Performance Effects of EIPH

The industry seems to offer a chicken-and-egg conundrum of how EIPH relates to performance; some say bleeding causes poorer performance, while some say that bleeders are performing better and working harder, which is why they bleed. So who's right? Some studies have found no association between the two, but others have. Hinchcliff described in particular one study of Australian racing Thoroughbreds that sought to answer this question.

Of 744 horses flat racing in Melbourne without furosemide, horses with grade 2 EIPH were 4.03 times less likely to win than those with no EIPH or grade 1 EIPH. Horses graded 3 or 4 were 2.178 times less likely to place in the top three. And as EIPH grade increased, so did the number of lengths affected horses finished behind the winner.

Earnings were also significantly affected--horses with no EIPH or grade 1 EIPH were 3.03 times more likely to be in the top 10% of money earners than horses with more severe disease. Grade 2-4 EIPH was associated with a lower likelihood of winning or placing.

Hinchcliff noted that a study evaluating EIPH's effects on career longevity was in progress.

Diagnosis

Hinchcliff briefly discussed multiple means of diagnosing EIPH, including videoendoscopy (examination of the airways with a camera on the end of a long probe) and BAL. He reported that endoscopy is more commonly used, more convenient for routine use in racehorses, and has good agreement between multiple evaluators.

He said BAL is more invasive, must be done under sedation, and might give a false negative result if the area washed is not an area that is bleeding.

The grading scale for endoscopic examination of EIPH is as follows:

• Grade 0: No blood detected in the pharynx, larynx, trachea, or mainstem bronchi.
• Grade 1: Presence of one or more flecks of blood or two or fewer short (less than one-quarter the length of the trachea) and narrow (less than 10% of the tracheal surface area) streams of blood in the trachea or mainstem bronchi (the two airways the trachea splits into; these carry air to and from the right and left lungs) visible from the tracheal bifurcation.
• Grade 2: One long stream of blood (more than one-half the length of the trachea) or more than two short streams of blood occupying less than one-third of the tracheal circumference.
• Grade 3: Multiple, distinct streams of blood, covering more than one-third of the tracheal circumference, with no blood pooling at the thoracic inlet.
• Grade 4: Multiple, coalescing streams of blood covering more than 90% of the tracheal surface with blood pooling at the thoracic inlet.

EIPH Treatments

Despite the impact of EIPH on equine health and the racing industry, researchers haven't yet been able to determine its exact causes or develop a universally effective treatment. "Proposed causes of EIPH include high blood pressure in the lungs, blood clotting disorders, small airway disease, impact-wave trauma, blood thickness, and upper airway obstruction, which probably all factor in in some way," said Hinchcliff. "With no clear etiology, it is very tough to have one clear treatment."

The diuretic (increases urinary output) medication furosemide is used worldwide in an attempt to combat the disease, including in the United States, Canada, parts  of South America, Saudi Arabia, and the Philippines. In the Breeder's Cup in 1990, 40% of horses raced on it, and in 2002, that rose to 90%. Different U.S. tracks averaged 92% usage in May-June 2001, he reported.

The effect of furosemide on severity or frequency of EIPH in race horses has not been demonstrated, in Hinchcliff's opinion. The medication is commonly used and it does result in horses performing better, with one study finding that treated horses were much more likely to win and finish in front by up to a second. However, whether this effect on performance is due to reduction in the severity of EIPH in affected horses, or because of the lower body weight (10-20 pounds) of treated horses, is unknown.

Other medications used to treat EIPH include hypotensive agents, bronchodilators, inhalants, and herbal/naturopathic remedies.
In summary, Hinchcliff stated, "EIPH is a highly prevalent, expensive disorder, with variable expression between horses and over time, which impairs performance. It likely impairs career longevity, and treatment is not well defined. We need a precise accounting of the costs of EIPH, its effects on well-being and career longevity/productivity, risk factors including heritability, the efficacy of furosemide, and control/prevention."

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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