Managing RAO: A Review of the Evidence

Recurrent airway obstruction (RAO) remains the most common cause of chronic coughing in temperate countries. Disease risk relates to both genetic susceptibility (Jost et al. 2007) and the airborne environment within the horses’ breathing zone, determined both by exposure to an organic dust source and the ventilation of the stable (McGorum and Pirie 2008).

The clinical signs of RAO during exacerbation largely reflect disease-associated lower airway obstruction resulting from a) bronchospasm; b) mucus plugging of airway lumina; c) airway wall thickening; and d) peribronchiolar infiltration (Robinson et al. 1995). These events, if sufficiently severe, result in the development of expiratory dyspnoea. However, due to improved disease awareness amongst horse owners, cases are increasingly presented early in the disease course, when symptoms are relatively subtle (occasional coughing and mild exercise intolerance). [...]