Types of Equine Asthma

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Types of Equine Asthma


Mild-to-Moderate Equine Asthma, previously Classified as IAD, is typically a respiratory disease that affects young to middle aged horses, as young as yearlings. Horses with Mild-to-Moderate Asthma do not show signs of respiratory difficulty at rest but may cough, have increased mucus in the trachea, and have decreased performance.This disease differs from Severe Equine Asthma, in that affected horses typically do not show increased respiratory efforts at rest.The exact cause is unknown, but is thought to be associated with inhalation of irritants such as barn dust and air pollution.


Severe Equine Asthma, previously RAO “Heaves/Broken Wind” or COPD, is a chronic airway disease that tends to be seen in older horses, usually from 6 years onwards. Horses with Severe Equine Asthma tend to have respiratory difficulty at rest, increased effort and rate of breathing, flaring of the nostrils, coughing, and mucus in the trachea and occasionally in the nostrils. Due to these difficulties associated with Severe Equine Asthma, a horse works harder to pull air into and expel air from the lungs than a healthy horse. This increased respiratory work forces the horse to use its abdominal muscles during the late phase of exhalation. Over time, the additional workload results in the visible enlargement of the abdominal muscles and the formation of what is known as a “Heave line”.