Exposure to respirable silica contributes to lower airway inflammation in asthmatic horses.
Authors: Romolo Alessandra, Costa Giulia, Sica Beatrice, Memoli Giulia, Ardit Matteo, Di Benedetto Francesco, Bellis Donata, Capella Silvana, Belluso Elena, Bullone Michela
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Respirable Silica and Equine Lower Airway Inflammation Chronic lower airway inflammation (equine asthma) is multifactorial, but respirable mineral particles—particularly silica—have received minimal attention as a contributor to disease pathogenesis. Researchers compared bronchoalveolar lavage fluid (BALF) samples from 23 horses (11 with moderate asthma, 7 with severe asthma, and 5 healthy controls) using polarised light microscopy to visualise intracellular silica particles and spectrometry-based analysis to quantify mineral composition. Severely asthmatic horses showed markedly elevated silica concentrations (1758 particles/mL, 20% of total mineral) compared to moderately affected animals (867 particles/mL, 8%) and controls (355 particles/mL, 6%), with a direct association between silica load and neutrophil counts in BALF. These findings suggest respirable silica is a genuine inflammatory driver in equine asthma rather than an incidental finding, implicating stable management practices—particularly bedding type, forage dust exposure, and arena surfaces—as significant modifiable risk factors. For practitioners managing asthmatic horses, this work strengthens the rationale for minimising dust-generating environments and selecting low-silica bedding materials as core therapeutic strategies alongside pharmacological intervention.
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Practical Takeaways
- •Respirable silica exposure should be considered as a potential risk factor for equine asthma; evaluate stable management practices and forage quality to minimize dust and mineral particle inhalation
- •Horses with persistent or worsening asthma despite standard management may benefit from environmental assessment focusing on dust control, improved ventilation, and reduced bedding/hay mineral content
- •Bronchoalveolar lavage with spectrometry analysis can identify silica burden in asthmatic horses and may help guide targeted environmental modifications
Key Findings
- •Intracellular birefringent silica particles were significantly elevated in severely asthmatic horses (12 particles/30 hpf) compared to moderately affected (4 particles/30 hpf) and controls (4 particles/30 hpf; P=0.01 and P=0.02 respectively)
- •Silica concentration in BALF was 1758 particles/mL in severely asthmatic horses versus 867 particles/mL in moderately affected horses and 355 particles/mL in controls (P=0.009 and P=0.0003)
- •Silica load in BALF was associated with neutrophilic airway inflammation in both moderately and severely asthmatic horses
- •Respirable silica may be an overlooked but significant contributor to chronic asthma development in horses