Practical approach to diagnosis, treatment and prevention of asthma

The term “equine asthma” describes a syndrome that encompasses a spectrum of severity of chronic airway inflammation. Previously, it was designated into two separate conditions – a milder and reversible condition termed equine inflammatory airway disease (IAD) and a more severe condition termed recurrent airway obstruction (RAO), associated with marked exercise intolerance and respiratory distress, including at rest.

A third, less commonly diagnosed condition, termed pasture-associated recurrent airway obstruction, also occurs in the UK and results in a similar spectrum of clinical manifestations, but is associated with exposure to pasture allergens in horses kept at pasture.

However, due to the relative rarity of this condition, further discussion is beyond the scope of this article. Equine asthma is a common disease among equids throughout the world, particularly during periods of increased stabling. Regardless of the disease severity in an individual, the clinical outcome is the development of inflammatory changes within the lower respiratory tract, including varying severities of leukocyte profile aberrations within the bronchoalveolar lavage fluid (BALF) and varying degrees of altered respiratory function – hence exercise intolerance and reduced performance.

The severity and chronicity of the airway inflammation generally dictates the reversibility, as well as the severity, of clinical signs and the effects on performance.

Diagnosis

Management of asthma

Prevention

Conclusion

Maintaining an optimal environment for equine patients is critical to the management and prevention of equine asthma. However, unfortunately, owner understanding of the degree of environmental management required, and compliance with these measures of control, is often poor, leading to treatment failure. In addition, and contradictory to the body of evidence available in the literature, often a dependency exists on bronchodilators for long-term management of equine asthma.

The appropriate approach to long-term management involves a combination of permanent environmental management and the use of corticosteroids as required in severe cases. This common misconception about treatment may be, in part, responsible for treatment failure or perceived poor responses in some cases. The reliance on cytological analysis of TWF compared with BALF may also be resulting in inaccuracy, with both diagnosis of severity and monitoring of response to management in these patients.

As a result, educating owners about the importance of using reliable diagnostic tests, and the vigilant manner they require to manage the equine environment, is important long term for controlling equine asthma.