Texas Equine Veterinary Association

www.texasequineva.com | 15 related breeds, and race on frequent schedules (Stricklin, 1998). Races are short sprints in both indoor and outdoor sand arenas, and in Texas oen at high environmental temperatures (100–110 °F), therefore, potentially worsening the underlying asthma. Dust exposure found in arenas due to increased use, and high environmental temperatures have been shown to exacerbate airway inflammation in asthmatic horses (Bullone et al., 2016; Lühe et al., 2017; McGorum et al., 1998; Pirie et al., 2003; Wheeler et al., 2006). We recently performed a study to evaluate the BAL fluid cytology results of barrel racing horses in northern Texas with EIPH, asthma or both diseases concurrently. We also wanted to evaluate the relationship between a previous medical history of EIPH and the development of non-infectious respiratory disease, in this case asthma. e study showed a substantial percentage (44%) of the horses examined had evidence of both EIPH and equine asthma on BAL cytologic evaluation. Equine asthma and EIPH remain common, but understudied problems in barrel racing horses. Improved understanding of EIPH and asthma in this population would assist in directing further research in non-infectious respiratory disease. While a history of EIPH was not associated with a diagnosis of EIPH on BAL, this was most likely due to the lack of timely BAL evaluation to the race event or bleeding episode. Further studies that consistently evaluate horses immediately following exercise are warranted to determine relationships between a history of previous EIPH bleeding episodes and diagnosis of EIPH on BAL fluid cytology. Our lab's results were consistent with previous studies, which reported no BAL cytological differences of inflammatory cells between horses diagnosed with EIPH and those without a diagnosis of EIPH (da Silva et al., 2017). Previous studies have demonstrated that the induction of pulmonary inflammation increased the likelihood of collecting erythrocytes in BALs conducted shortly aer high-speed exercise (McKane and Slocombe, 2010). Our study's findings were consistent with similar findings in young oroughbred racehorses where there was an association of inflammatory airway disease (IAD) and EIPH reported (Newton and Wood, 2002). Although an infectious cause of respiratory disease did not affect that association, a specific temporal relationship between an EIPH bleeding event and subsequent asthma has not been established (Newton and Wood, 2002). Previous research has been inconclusive on the best intervention for inflammation secondary to pulmonary blood exposure (Walker et al., 2006). e relationship between EIPH and equine asthma is a diagnostic challenge for practitioners evaluating the performance horse. Lower airway endoscopy to evaluate EIPH has the advantage of speed of assessment, grading of severity of EIPH, and immediate decision making. However, lower airway endoscopy will not provide information on the significance of lower airway inflammation in those horses. Bronchoalveolar lavage provides superior diagnostic information for equine asthma and for non-acute EIPH; however, there is an increased time to receiving results. Additionally, the BAL examination requires sedation, which may not be appropriate depending on the horse's competition schedule. e results of this study support that a diagnosis of EIPH made by lower airway endoscopy may require a BAL in order to fully characterize the respiratory disease in the individual horse. Additionally, the BAL may be the appropriate first diagnostic test in a horse suspected of EIPH and has additional risk factors for equine asthma. Recent studies have investigated the use of various biomarkers in the diagnosis of equine asthma (Gy et al., 2019). Further work on a specific biomarker for pulmonary inflammation would be a significant aid in cases with multiple concurrent airway diseases, as general inflammatory biomarkers are not sufficiently specific to provide a diagnosis or direct treatment (Leclere et al., 2015). Further, studies evaluating the anti-inflammatory response to treatment in horses diagnosed with EIPH are warranted. Barrel-racing horses with evidence of EIPH are commonly treated with furosemide. e administration of furosemide has shown to have minimal, but positive, effects on the respiratory function of horses with equine asthma (Broadstone et al., 1991; Calzetta et al., 2017; Rubie et al., 1993). While the administration of furosemide is unlikely to fully mask the signs of severe equine asthma, it is possible that furosemide coupled with management changes following a bleeding event such as reduction in highly strenuous training sessions and use of nasal strips, may be sufficient to mask signs of equine asthma in mild cases. e use of the BAL as a diagnostic tool in this population may be useful to detect disease that would be diagnosed subsequently or otherwise mis-diagnosed. Environmental modifications remain an appropriate recommendation for horses diagnosed with asthma (Couëtil et al., 2016). Barrel racing horses, by the nature of their use, are required to have frequent high intensity exercise in closed arenas with high particulate load in the air, thus providing high antigenic stimulation (Bond et al., 2018). e ongoing investigation of allergic versus nonallergic asthma in horses may also explain the different response to treatment in horses with asthma alone compared to horses diagnosed with both EIPH and asthma (Bond et al., 2018). Allergy testing of horses is likely to be required to fully characterize allergic asthma, as is currently performed in humans (Bond et al., 2018). Further studies will be required to determine the prevalence of these diseases in the barrel-racing population and to evaluate the relative risk to this population. Comorbidities of EIPH and asthma were a common diagnosis (44%) in barrel racing horses in our study. Horses with EIPH and asthma were unlikely to be diagnosed with severe asthma compared to horses with asthma alone. Work on the pathophysiologic relations between the two diseases is necessary to further explore this relationship and establish the most appropriate treatment. Bronchioalveolar lavage of horses suspected of EIPH is warranted to fully characterize the noninfectious respiratory disease of performance horses, especially horses competing in closed environments such as arenas. I would like to thank Dr. Ty Tipton of 113 Equine for the invitation to write this article for the TEVA Remuda. Laszlo Hunyadi, DVM, MS, DACVIM (LAIM) Professor of Large Animal Internal Medicine & Tropical Medicine Texas Tech University School of Veterinary Medicine Amarillo, TX

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