Environmental heat and airborne pollen concentration are associated with increased asthma severity in horses.
Authors: Bullone M, Murcia R Y, Lavoie J-P
Journal: Equine veterinary journal
Summary
# Environmental Heat and Pollen: New Triggers for Equine Asthma Exacerbations Whilst severe equine asthma (SEA) has long been associated with winter stabling and dust exposure, this 2016 retrospective analysis of 14 clinically asthmatic horses reveals that elevated environmental temperature and humidity present an equally significant—and often overlooked—trigger for disease exacerbation. Researchers correlated daily clinical asthma scores with barn conditions and measured lung function parameters (transpulmonary pressure, pulmonary resistance, and elastance) under hot (25°C) versus warm (18°C) conditions, finding statistically significant positive correlations between mean daily clinical scores and both temperature (r = 0.58) and air enthalpy (r = 0.55), with higher temperatures also driving increased airborne pollen concentrations. Critically, when barn temperature increased, horses demonstrated measurably worse lung mechanics—increased transpulmonary pressure, pulmonary resistance, and elastance—independent of any management changes. For equine practitioners managing asthmatic horses, these findings suggest that temperature control and environmental cooling warrant equal emphasis with dust mitigation strategies, particularly during warm weather periods; additionally, clinicians should account for seasonal temperature fluctuations and pollen counts when assessing treatment response, as apparent therapeutic failure may actually reflect uncontrolled environmental triggers rather than inadequate medical intervention.
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Practical Takeaways
- •Cool, well-ventilated barn environments help reduce asthma severity during disease exacerbations in affected horses
- •Environmental temperature and pollen concentration should be documented when assessing treatment response to asthma therapy
- •Monitor asthmatic horses more closely during heat events and high pollen days, as these conditions independently worsen airway obstruction
Key Findings
- •Mean daily clinical asthma scores correlated positively with barn temperature (r = 0.58, P = 0.01) and air enthalpy (r = 0.55, P = 0.02)
- •Maximal daily temperature correlated with airborne pollen concentrations (r = 0.51, P = 0.0002)
- •Higher barn temperature and enthalpy increased transpulmonary pressure (P = 0.005), pulmonary resistance (P = 0.008), and elastance values (P = 0.005)
- •Clinical signs worsened during heatwaves in addition to the previously recognized winter exacerbations