Airway wall eosinophilia is not a feature of equine heaves.

Summary

# Equine Heaves and Airway Eosinophilia: What Dubuc and Lavoie Found Whether eosinophilic inflammation underpins the pathophysiology of equine heaves has remained unclear, prompting Dubuc and Lavoie to examine airway wall tissue from six acute heaves cases and six age-matched controls using Luna's staining and quantitative histomorphometry. Counter to expectations, total eosinophil counts per mm² of basement membrane were significantly *lower* in heaves-affected horses compared to controls, with intraluminal, intraepithelial, and airway smooth muscle eosinophil populations all reduced in the disease group. These findings fundamentally challenge the theory that eosinophilic infiltration drives the obstructive airway remodelling and mucus production characteristic of heaves, suggesting instead that other inflammatory pathways—such as neutrophilic or lymphocytic mechanisms—warrant greater investigative focus. For practitioners managing heaves cases, this work reinforces that the condition's persistent bronchoconstriction and airway obstruction are unlikely to be primarily eosinophil-mediated, which may have implications for anti-inflammatory treatment selection and the rationale for certain pharmacological interventions.

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Key Findings

• •Total eosinophil counts in airways were significantly higher in control horses than heaves-affected horses (per mm² basement membrane)
• •Intraluminal, intraepithelial, and airway smooth muscle eosinophil counts were all elevated in control horses compared to heaves-affected horses
• •Eosinophil infiltration does not appear to contribute to persistent airway obstruction in equine heaves

Conditions Studied

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