Evaluation of nebulised hay dust suspensions (HDS) for the diagnosis and investigation of heaves. 1: Preparation and composition of HDS.
Authors: Pirie R S, McLachlan G, McGorum B C
Journal: Equine veterinary journal
Summary
# Editorial Summary Equine recurrent airway obstruction (heaves) diagnosis traditionally relies on exposing susceptible horses to dusty hay, but this approach suffers from inconsistent results owing to variable organic dust content and composition between hay batches. Pirie and colleagues addressed this limitation by developing standardised hay dust suspensions (HDS) derived from fine particulates collected from dusty hay, then characterising their biochemical and physical properties including endotoxin and β-D-glucan concentrations, protease activity (dominated by a 28 kDa serine protease and 85/160 kDa metalloproteases), and particulate size distribution. Critically, both soluble and particulate components of the HDS proved suitable for nebulisation delivery to the respiratory tract using standard jet nebuliser equipment. This standardised challenge system substantially reduces experimental variability compared to conventional hay exposure, enabling more reliable and reproducible diagnosis of heaves whilst simultaneously permitting systematic investigation of which dust components (endotoxins, fungal antigens, proteases) drive the airway inflammatory response. For practitioners and researchers, nebulised HDS offers a more controlled alternative to dusty hay challenges, with potential applications in validating therapeutic interventions and identifying individual horses' specific dust sensitivities with greater precision.
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Practical Takeaways
- •Nebulised hay dust suspensions offer a more standardised and reproducible method for diagnosing heaves compared to exposing horses to variable dusty hay sources
- •The detailed characterisation of HDS components (endotoxins, glucans, proteases) enables better understanding of which dust components trigger heaves responses
- •This technology could improve consistency in heaves investigation and diagnosis protocols across different facilities and research settings
Key Findings
- •Hay dust suspensions (HDS) were successfully prepared from fine dust particles comprising mostly fungal spores collected from dusty hay batches
- •Protease activity in HDS was mainly attributable to a 28 kDa serine protease and 85 kDa and 160 kDa metalloproteases
- •Both particulate and soluble components of HDS could be effectively aerosolised using jet nebulisation techniques
- •Nebulised HDS provides a standardised challenge system with reduced variability compared to conventional dusty hay/straw exposure