Risk Factors for EIPH in Australian Racehorses Studied

Researchers know that exercise-induced pulmonary hemorrhage, or EIPH, can hinder a horse's lung function and athletic performance. What they're still not clear on, however, is which horses will bleed and when. But an Australian research team recently took a step closer to finding the answer.

Ellie Crispe, BSc, BVMS, a resident in equine surgery and medicine at Murdoch University, in Murdoch, Western Australia, and colleagues recently set out to identify EIPH risk factors in a population of Australian racehorses. She shared the study's results during a poster presentation at the 2014 American College of Veterinary Internal Medicine Forum, held June 4-7 in Nashville, Tennessee.

At least 30 minutes after each race, the team performed tracheobronchial endoscopy on 583 racehorses competing at tracks in Perth, Australia. Experienced clinicians (blinded to the horse's identity, race performance, and other factors) evaluated each horse and scored its EIPH on a 5-point scale (with 0 being no evidence of EIPH and 4 being severe EIPH). The team also collected and evaluated 28 horse-, track-, equipment-, and climatic-related variables to pinpoint risk factors.

Upon reviewing their results, Crispe and colleagues found that:

  • Of the 583 horses examined endoscopically, 330 (56.6%) showed evidence of EIPH;
  • Of those, 159 were classified as Grade 1 bleeders, 111 as Grade 2, 45 as Grade 3, and 15 as Grade 4;
  • Low ambient temperatures were associated with an increased risk of EIPH;
  • Horses that had 20 or more lifetime starts were more likely to develop EIPH than horses with fewer lifetime starts;
  • Longer race distance increased the chance of EIPH; and
  • Horses wearing one or more bar shoes were more likely to bleed than horses not shod with bar shoes.

While scientists have implicated temperature and increased race distance as EIPH risk factors in the past, Crispe said the bar shoe data is a "novel horse-level finding." But bar shoes' association with EIPH is still unclear.

"Unfortunately, we don’t have information as to why the horses’ were wearing bar shoes as opposed to normal shoes," she explained. "It may relate to increased vascular pressure, both in magnitude and duration, associated with higher foot pain."

Crispe said her EIPH research is ongoing: "Our next research project involves examining Thoroughbred racehorses with endoscopy after racing, on multiple occasions throughout two racing preparations to determine how EIPH progresses from race to race."

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.

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