Equine Recurrent Airway Obstruction Study Guide
Overview and Clinical Importance
Recurrent Airway Obstruction (RAO), also known as heaves or severe equine asthma, is one of the most common chronic respiratory diseases affecting mature horses worldwide. This inflammatory, obstructive airway disease is characterized by reversible bronchoconstriction, excessive mucus production, and neutrophilic airway inflammation triggered by exposure to inhaled organic dusts and molds. RAO represents a significant category on the NAVLE and understanding its pathophysiology, diagnosis, and management is essential for clinical practice.
The condition shares many similarities with human asthma and is now classified under the umbrella term equine asthma syndrome, which encompasses mild-to-moderate equine asthma (formerly Inflammatory Airway Disease or IAD) and severe equine asthma (formerly RAO/heaves). A related condition, Summer Pasture-Associated Obstructive Pulmonary Disease (SPAOPD), affects horses on pasture during warm, humid months.
Etiology and Pathophysiology
Triggering Factors
RAO is initiated by inhalation of organic dusts containing a complex mixture of allergens and irritants. The primary offending agents include:
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