Airway inflammation and mucus in two age groups of asymptomatic well-performing sport horses.
Authors: Gerber V, Robinson N E, Luethi S, Marti E, Wampfler B, Straub R
Journal: Equine veterinary journal
Summary
Horses kept in conventional stables face persistent exposure to airborne dust and organic particles, raising questions about whether this chronic challenge produces detectable airway changes even in clinically normal, high-performing animals. Gerber and colleagues examined bronchoalveolar lavage fluid (BALF) cytology and endoscopic assessment of mucus in 13 younger (mean 5 years) and 13 older (mean 15 years) sport horses with no history of respiratory disease, comparing inflammatory markers and mucus accumulation between the groups. Remarkably, all 26 horses demonstrated evidence of subclinical inflammatory airway disease (IAD), yet older horses—exposed to conventional stabling for an additional decade—showed no greater inflammation or mucus load than their younger counterparts; the only significant difference was elevated total and lymphocyte cell counts in younger horses. Notably, endoscopic mucus scoring (quantity and quality) showed no correlation with BALF neutrophil percentages, suggesting that visual assessment of mucus and cytological inflammation may reflect different pathological processes. For practitioners, these findings underscore that subclinical airway changes are the norm rather than exception in stabled sport horses, but the authors appropriately caution that the clinical relevance of these findings to athletic performance remains unclear and warrants investigation in discipline-specific populations.
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Practical Takeaways
- •Conventional stable housing environments expose all sport horses to subclinical airway inflammation; consider environmental management strategies (ventilation, bedding type, dust control) even for clinically healthy performers
- •Age alone does not predict increased subclinical airway disease in sport horses, but the clinical significance of subclinical IAD on athletic performance remains unclear and warrants investigation
- •Visual endoscopic assessment of mucus does not reliably predict inflammatory cytology findings; clinical evaluation should consider both endoscopic and cytological data when assessing subclinical airway disease
Key Findings
- •All 26 asymptomatic well-performing sport horses housed in conventional stables showed evidence of subclinical IAD regardless of clinical health status
- •Older horses (mean 15 years) did not show increased airway inflammation or mucus compared to younger horses (mean 5 years) despite 10 additional years of dust exposure
- •Younger horses had significantly increased BALF total and lymphocyte cell counts compared to older horses
- •Mucus quantity and quality scores were not significantly correlated with BALF neutrophil percentages, suggesting endoscopic and cytological findings measure different aspects of airway disease