Histology, prevalence, and environmental sources for pulmonary silicates depositions in domestic and wild animals.
Authors: Walker Randall T, Illanes Oscar, Conan Anne, Williams Bruce H, Hilchie David, Bolfa Pompei
Journal: Veterinary pathology
Summary
# Pulmonary Silicate Deposition in Horses and Other Animals: A Caribbean Study Silicate crystals accumulate in the lungs of many animals, yet their origin and clinical significance remain unclear. Researchers examined lung tissue from nine species (including horses, cattle, and chickens) in St. Kitts using light microscopy, scanning electron microscopy with energy-dispersive x-ray analysis, and x-ray diffraction to characterise the mineral composition and prevalence of these deposits. Crystalline silicate material appeared in 77.6% of the 259 samples analysed, predominantly as silicate-laden macrophages in the perivascular and interstitial spaces, with mongooses showing the highest burden (100% prevalence, median severity grade 3 of 3) and horses and cattle similarly affected; notably, most animals showed minimal chronic inflammation or fibrosis despite substantial particle deposition. Environmental analysis identified Saharan dust, volcanic ash, topsoil, and quarry dust as probable sources of the inhaled particles (sized 2.5–10 µm), with vehicle traffic and wind likely amplifying exposure. For equine practitioners, these findings suggest that respiratory silicate accumulation in horses may be a consequence of environmental exposure rather than an inherent pathology, though the long-term implications for performance, recurrent airway obstruction, and other respiratory comorbidities warrant further investigation—particularly in operations where dust generation from arena surfaces, hay handling, or herd movements is significant.
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Practical Takeaways
- •Horses in dusty environments (particularly arid regions with volcanic or desert dust exposure) may accumulate silicates in lungs without obvious clinical signs; monitor respiratory health in such settings
- •Pulmonary silicate deposition appears to be an environmental rather than occupational hazard in animals; dust control measures (road watering, ventilation in stables) may reduce exposure
- •The absence of inflammatory response in most cases suggests silicate inhalation may be asymptomatic, but further research is needed on whether it predisposes to secondary respiratory disease
Key Findings
- •Crystalline silicate material was present in 77.6% (201/259) of lung samples across multiple animal species, predominantly as silicate-laden macrophages
- •Mongooses showed 100% prevalence and most severe lesions (median grade 3), followed by monkeys at 98% prevalence with median grade 2 severity
- •Silicate particulate matter ranged from 2.5–10 μm in diameter and originated from environmental sources including Saharan dust, volcanic ash, topsoil, and quarry dust
- •Silicate accumulations in lungs generally lacked chronic inflammation or fibrosis, distinguishing environmental silicate exposure from classic occupational silicosis