Association between cough and cytology of bronchoalveolar lavage fluid and pulmonary function in horses diagnosed with inflammatory airway disease.
Authors: Bedenice D, Mazan M R, Hoffman A M
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Cough and Inflammatory Airway Disease in Horses Researchers examined 137 performance horses presenting with signs of inflammatory airway disease (IAD) to understand whether chronic cough reliably indicates specific patterns of airway inflammation and dysfunction. Using bronchoalveolar lavage (BAL) cytology, pulmonary function testing, and airway reactivity assessments, they performed multivariable logistical regression analysis to identify which clinical and pathological findings best predicted cough presentation. Elevated BAL neutrophil counts (>5%) and concurrent nasal discharge emerged as the strongest indicators of cough, particularly in horses older than seven years; however, measures of lung mechanics and exercise intolerance did not statistically correlate with cough once other variables were accounted for. Notably, whilst airway hyper-responsiveness showed no association with neutrophilic inflammation, it was significantly linked to elevated BAL mast cells (>2%)—suggesting distinct inflammatory pathways underlie different clinical signs. These findings have important diagnostic value: cough can serve as a practical clinical indicator of neutrophilic airway inflammation in low-grade nonseptic IAD, though practitioners should recognise that airway reactivity may reflect mast cell involvement rather than neutrophilic disease, and that abnormal lung function or poor exercise tolerance may persist independently of cough presentation.
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Practical Takeaways
- •In horses >7 years presenting with cough and nasal discharge, suspect neutrophilic airway inflammation even if lung function tests appear relatively normal—BAL cytology is warranted for confirmation
- •The presence of cough does not necessarily indicate mechanical airway obstruction; neutrophilic inflammation can cause cough independently, which has implications for treatment selection and prognosis
- •Differentiate between cough (neutrophil-driven) and exercise intolerance/airway obstruction (potentially mast cell-driven) as they may reflect distinct pathophysiological processes requiring different therapeutic approaches
Key Findings
- •Cough was significantly more prevalent in horses >7 years and characterized by high BAL neutrophil count (>5%) and nasal discharge
- •Neutrophilic airway inflammation (BAL neutrophils >5%) was associated with cough but did not significantly affect respiratory mechanical function
- •Airway hyper-responsiveness was significantly associated with BAL mast cells >2% rather than neutrophilic inflammation
- •Cough may serve as a clinical indicator of neutrophilic airway inflammation in nonseptic respiratory disease