Chronic obstructive pulmonary disease (COPD), commonly referred to as “heaves”, is a major problem for horses and horse owners in the south. COPD or heaves is a respiratory condition that is caused by an allergic reaction to molds that are found in the pastures and dust found in hay and barns. It routinely occurs in the hot humid summer months July, August, and September, but some horses can experience problems earlier and/or later in the year.
Horses with mild cases will exhibit a mild increase in their respiratory rate (about 20 breaths per minute) and may have a nasal discharge. Severely affected horses will have a high respiratory rate (40 breaths per minute or higher), a hard abdominal push when exhaling, a deep dry cough and a thick nasal discharge. Over time the hard abdominal push can result in an over development of the abdominal muscles causing a “heave line”. The difficulty in breathing is a result of mucus build up and narrowing of the airways due to bronchospasms. This narrowing causes a “wheezing” sound at the end of expiration. The constant struggle to get adequate oxygen causes inflammation in the lungs. This inflammation, if left untreated, can result in permanent damage. Some horses will show a decrease in energy and have significant weight loss.
Treatment is directed at reducing exposure to allergens and correcting the changes in the lungs. Environmental modifications are the first step in treating heaves. Molds growing in the seed heads of mature grass are primary allergens. Keeping pastures cut short on a regular basis is important. Although this will help, it can be difficult to significantly reduce exposure to horses that are out on pasture. This can mean that some horses may need to be kept in stalls. Once in the barn, dust and hay allergens must be controlled. Soaking the hay and lightly misting the shavings in the stall will help control the dust. In severe cases stalls may need to be enclosed and air-conditioned.
Most horses that develop COPD will need medication during the problem months. Medications are typically given orally or aerosolized and inhaled. The foundation for treating heaves medically is decreasing the inflammation in the lungs. Steroids are frequently used with bronchodilators to increase the success of treatment. Several types of bronchodilators are available in metered dose inhalers (MDI’s). The response to treatment is usually immediate but short lived. These drugs can be used alone or in combination to increase the effectiveness of treatments.
The effectiveness of treatment depends on using as many environmental modifications as possible and a careful balance of medications. There is no cure for heaves and once the horse has developed an allergy to the mold and dust, signs may reoccur year after year. Oral medications are still the most common drugs prescribed because of their cost and ease of use. Supplements and cough medications can round out the complete treatment list. Regardless of the options chosen, your veterinarian can create a treatment plan that has the best chance of helping your horse deal with heaves.