Chronic Obstructive Pulmonary Disease (COPD; "Heaves")

Rachele J. Baker

We want to purchase a gentle, older horse for our daughter to learn to ride. We found a horse that our daughter loves, but our friend says the horse has "heaves." What is "heaves?"

Heaves (also called Chronic Obstructive Pulmonary Disease or COPD) is an equine lung disease caused by an allergic reaction to inhaled particles (allergens). It is similar to human asthma. The allergens that cause the clinical signs of heaves are found primarily in hay. Hay contains bacteria, fungi, and other tiny particles that become aerosolized in hay dust. When a COPD-afflicted horse inhales these particles, it has an allergic reaction which results in inflammation and constriction of the airways (the trachea, bronchi, and bronchioles). The horse may exhibit such clinical signs as "heaving" towards the end of exhalation to push air out of the lungs through the constricted airways, coughing, wheezing, and nasal discharge. A horse with heaves may also have exercise intolerance and may lose weight due to the difficulty of eating when normal breathing is impaired. Heaves is most often seen in older horses (greater than six years old). Although COPD does not appear to be breed or gender related, there is evidence that it may be hereditary.

How is heaves (COPD) diagnosed?
Veterinarians usually diagnose chronic obstructive pulmonary disease based on history and clinical signs such as "heaving," coughing, wheezing, and nasal discharge. The veterinarian may also use an endoscope to visually examine the airways for evidence of inflammation or accumulated mucus.

Is there any treatment for heaves?
The easiest way to treat a horse with heaves is to minimize exposure to hay dusts by putting the horse out to pasture. Simply changing the environment of the horse in this manner will cause the horse to go into clinical remission. If the horse must be stabled, then eliminating hay dusts in the stable can be achieved by bedding the horse on shavings and feeding a low dust diet such as pelleted feed or alfalfa cubes. Horses in adjacent stalls preferably should be kept in the same manner to prevent hay dusts from contaminating the stall of the horse with heaves. Good ventilation in the barn is also important. This can be accomplished by keeping the windows and doors open whenever possible or by using ventilation systems.

Anti-inflammatory drugs such as corticosteroids may be required to relieve airway inflammation in COPD-afflicted horses. Corticosteroids can be administered by mouth, by injection, or by inhalation with the use of a special mask. Bronchodilator drugs may be safely combined with anti-inflammatory drugs for treatment of more severely affected horses. Bronchodilator drugs relax the smooth muscle surrounding the airways and relieve bronchoconstriction. Bronchodilators can also be administered orally, by injection, or by inhalation using a special mask.

This article was prepared by Rachele J. Baker under the direction of the faculty and staff of the Equine Pulmonary Laboratory, College of Veterinary Medicine, Michigan State University. For a more detailed discussion (including illustrations) on this subject, please see the article entitled: Chronic Obstructive Pulmonary Disease at the Equine Pulmonary Laboratory at Michigan State University.