Horses with Heaves
by Dr. Ed Millhouse

Recurrent Airway Obstruction or RAO

Heaves, formerly known as COPD (Chronic Obstructive Pulmonary Disease,) is a manageable and sometimes reversible equine lung disease caused by an allergic reaction to inhaled particles. It is similar to human asthma. The allergens that cause clinical signs of heaves are found primarily in dust from hay and bedding. When an RAO-afflicted horse inhales these particles, it has an allergic reaction which results in inflammation and constriction of the lower airways. The horse may exhibit clinical signs such as “heaving” towards the end of exhalation to push air out of the lungs through constricted airway, coughing, wheezing and nasal discharge. A horse with heaves may also exhibit exercise intolerance and lose weight due to difficulty breathing when normal breathing is impaired. Heaves is most often seen in horses over six years of age in northern climates where they are stabled indoors and fed hay, especially round bales.
Heaves is diagnosed based on the history and clinical signs of “heaving,” coughing and nasal discharge. Blood work and other imaging and diagnostic tests may be needed to confirm heaves or exclude other respiratory disease.
The easiest way to treat a horse with heaves is to minimize exposure to hay and bedding dust by turning the horse out to pasture 24 hours a day. Simply changing its environment can cause a horse to go into clinical remission. If the horse must be

stabled, then eliminate dust in the stable by bedding the horse on pelleted shavings and feeding a low dust diet such as pelleted or molasses covered feed, hay cubes or soaked hay. Good ventilation in the barn is vital.
Medication may be needed either occasionally or long term to manage episodes of heaves. Corticosteroids, bronchodilators, and antihistamines can be used in combination or separately to control heaves. Corticosteroids are a potent and effective anti-inflammatory that suppress the allergic reaction but may cause side effects. Bronchodilators relax the smooth muscle surrounding the airways and relieve some of the respiratory distress. These can be used in times of respiratory distress or before exercising the horse. Antihistamines can be used to block the histamine release that causes the allergic reaction. Antibiotics may be needed as horses with RAO are more susceptible to respiratory infections.
The prognosis for cessation of the disease progression is good if rigorous continual prevention of exposure to dust is maintained and medical treatment is implemented as needed to control airway inflammation. The prognosis is highly dependent on the level of care that is provided and the horse owner’s willingness to undertake the measures necessary to maintain lung health of the horse for the rest of its life.

A heaves attack can be a medical emergency.
Call our office immediately if:

  • Pro longed respiratory distress, i.e. flared nostrils, wheezing, exercise intolerance
  • If the horse is Off-feed, weight loss, fever (temp greater than 102)
  • Thick opaque nasal discharge

Thank you to Dr. Millhouse for this information! Check out his website at for more!