Airway Hyperresponsiveness, but Not Bronchoalveolar Inflammatory Cytokines Profiles, Is Modified at the Subclinical Onset of Severe Equine Asthma.
Authors: Frippiat Thibault, Art Tatiana, Tosi Irene
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary This 2023 study investigated the relationship between airway hyperresponsiveness (AHR) and inflammation in severe equine asthma (SEA), specifically examining which develops first during subclinical disease onset. Researchers used impulse oscillometry and methacholine bronchoprovocation testing on horses in clinical remission versus healthy controls, then exposed both groups to a low-dust environment for one week whilst measuring clinical signs, endoscopic findings, bronchoalveolar lavage cytology, pulmonary function, and inflammatory cytokine profiles. Whilst both diagnostic tests proved sufficiently repeatable for clinical use, the key finding was that SEA horses developed increased AHR within one week of the environmental challenge despite showing no detectable airway inflammation, no changes in pro-inflammatory cytokine levels, and no differences in clinical presentation compared to controls. This temporal dissociation—where hyperresponsiveness precedes measurable inflammation—suggests equine asthma may follow a fundamentally different pathogenic pathway than the neutrophilic inflammation-driven model seen in human asthma, with important implications for how we monitor disease progression and interpret subclinical findings in at-risk horses. For practitioners, this indicates that functional airway tests detecting early hyperresponsiveness may offer a more sensitive window for intervention than traditional inflammatory markers, potentially allowing preventative management before clinical signs or cellular inflammation become apparent.
Read the full abstract on PubMed
Practical Takeaways
- •AHR may be detectable in horses with subclinical asthma before conventional clinical signs or inflammatory markers appear, allowing potential earlier detection and intervention
- •Environmental triggers (dust exposure) can provoke airway dysfunction in susceptible horses without visible inflammation, supporting the importance of stable management in asthma-prone horses
- •Equine asthma may follow a distinct disease mechanism compared to human asthma, suggesting treatment approaches may need to be tailored specifically for horses rather than extrapolated from human protocols
Key Findings
- •Pulmonary function testing and methacholine bronchoprovocation testing showed acceptable repeatability in equine asthma horses
- •SEA horses in clinical remission were indistinguishable from controls at baseline, unlike human asthma patients
- •After low-dust environmental challenge, SEA horses demonstrated increased airway hyperresponsiveness without corresponding inflammatory markers or pro-inflammatory cytokine changes
- •Airway hyperresponsiveness appears at an earlier disease stage than airway inflammation in equine asthma, suggesting a different pathophysiologic pathway than neutrophilic human asthma