Risk factors for exercise‐induced pulmonary haemorrhage in Thoroughbred racehorses

Abstract

SummaryReasons for performing study: Risk factors for occult exerciseinduced pulmonary haemorrhage (EIPH) are poorly defined or quantified. Objectives: To investigate the importance of putative risk factors for EIPH amongst Thoroughbred racehorses in Australia. Methods: Tracheobronchoscopy was used to determine EIPH status of 744 Thoroughbred racehorses after flat racing in Melbourne, Australia. Horses were identified for study before racing, and over 50% of horses racing during the study period were examined. Statistical analysis included use of bivariate and multivariate logistic regression analysis to account for simultaneous effects of a large number of variables. Results: The only risk factor identified as associated with both EIPH Ն1 or Ն2 was ambient temperature, with horses racing at temperatures <20°C being at~2 times risk of occult EIPH. There was no association of EIPH with age, sex, weight carried, track hardness, speed of racing, or air quality. Conclusions: There do not appear to be individual risk factors, amongst those examined in this study, that are strongly associated with EIPH. Potential relevance: The risk of developing EIPH cannot be readily determined from a combination of age, race speed, race distance, track hardness or air quality. This study does not provide support for the hypotheses that racing on hard surfaces or in polluted air contributes to the development of EIPH.

Tracheobronchoscopic Assessment of Exercise‐Induced Pulmonary Hemorrhage and Airway Inflammation in Barrel Racing Horses

“…This study describes the prevalence of EIPH (45.3%) and TMA (99.3%) in a sample population of barrel racing horses under normal racing conditions in Alberta. The prevalence of EIPH detected in this study is high; however, it was lower than the reported prevalence of EIPH (68 and 55%) in large‐scale Thoroughbred racehorse studies . The physiological adaptations of barrel racing horses are likely similar to those of racehorses, so it is not surprising that there is also a high prevalence of EIPH among barrel racers.…”

Exercise‐induced pulmonary haemorrhage in Thoroughbred racehorses: a longitudinal study

“…These pathological changes are likely progressive with continued racing. Single point observations have reported an association between EIPH and a cumulative racing measure, lifetime starts . In this study, inclusion of specific shorter‐term cumulative measures such as, the number of days in the current racing preparation were significantly associated with the EIPH score and progression modelling.…”

“…An inverse relationship between ambient temperature and EIPH has been identified in multiple studies . Ambient temperature was a persistently significant variable throughout these analyses; associated with the current EIPH score, the transition from a lower to a higher EIPH score and progression modelling.…”

Inflammatory Airway Disease of Horses—Revised Consensus Statement

“…The potential association between IAD and EIPH is controversial. One study reported increased risk of EIPH with the presence of lower airway inflammation,107 but other studies have found no significant correlation between hemosiderophage and neutrophil counts in BALF of horses with IAD33 as well as no association between EIPH and mucus score 108…”