Heaves, Severe Equine Asthma

It has been known (for many years) since antique time that horses develop a chronic and debilitating “asthma”-like disease when stabled and exposed to hay.  Many names have been used to describe this condition over the years (Heaves, equine COPD, Equine emphysema, Recurrent Airway obstruction …), which can lead to confusion.  Furthermore, some horses will rather develop these clinical signs when on pasture (Summer Pasture Associated Obstructive Pulmonary Disease), suggesting that different antigens may contribute to the disease.  We have recently proposed to use the term “Equine Asthma” because of the similarities with human asthma, both in terms of the natural history of the disease, the clinical presentation, and the response to therapy.

Human asthma is the most common chronic inflammatory diseases of the respiratory tract affecting 300 million people globally, and 2 million Canadians. The hallmarks of the disease are airway inflammation and remodeling. Despite development of effective therapy to control inflammation, asthma remains incurable.

Mild/Moderate Equine Asthma or Inflammatory Airway Disease (IAD)

IAD, or Inflammatory Airway Disease, is a term used to describe a non-infectious disease of the small airways in the horse. It is a highly prevalent disease in the equine species. IAD is a less severe form of asthma (Mild and Moderate Equine Asthma) with no respiratory distress at rest. The majority of horses will experience transient episodes of IAD in their lifetime, with an increase to the breath, which is observed in about 75% of horses at some point during their lifetime.