Dogs, cats, horses, and people develop spontaneous bronchoconstriction associated with airway inflammation and characterized by chronic cough and wheeze. Attacks of airway obstruction are induced by exposure of susceptible animals to antigens (typically hay dust, molds, and pollens). Effective therapy of allergic airway disease is species dependent because of the inflammatory mediators involved in bronchoconstriction. The pathogenesis of feline asthma differs from allergic airway disease in other species in that cats are exceptionally responsive to serotonin (5-hydroxytryptamine). Serotonin, which is released from degranulating mast cells, appears to be the major mediator of allergen-induced bronchoconstriction in cats. Cats also appear to suffer from chronic bronchitis, similar in clinical presentation to feline asthma; the main feature that differentiates these two conditions is the lack of bronchoconstriction in chronic bronchitis. In dogs, chronic bronchitis is an inflammatory, chronic pulmonary disease that results in cough and can lead to exercise intolerance and respiratory distress but is typically not characterized by severe bronchoconstriction. In horses, there are two clinical syndromes of airway inflammation. Recurrent airway obstruction, or “heaves,” is an inflammatory, obstructive airway disease clinically evident in middle-aged horses. Inflammatory airway disease is a low-grade inflammation of the small airways that is a common cause of poor performance in young to middle-aged, athletic horses. Inflammatory airway disease is typically not treated in ruminants or swine.
The goals of therapy for inflammatory airway disease are to prevent recurrent exacerbations of airway obstruction and reduce emergency visits and expenses, to provide optimal chronic anti-inflammatory therapy with minimal or no adverse effects, to maintain (near) “normal” pulmonary function, and to meet the owner's expectations of quality of life for their animal.