Horse Heaves: Symptoms and Treatment

That nagging little cough at the beginning of your rides, and that occasional runny nose could they mean your horse is suffering from recurrent airway obstruction, or RAO?

Possibly. This condition, commonly known as heaves, is the most prevalent lung disease seen in horses. Horse heaves is chronic and can threaten your horse’s long-term health and performance. Although your horse’s heaves can’t be cured, and severe cases are difficult to manage, catching it early will help you manage it as well as possible, and perhaps minimize its damage to your horse’s lungs.

Here, I’ll give you a checklist of horse heaves symptoms to help you know when to alert your veterinarian, so he or she can begin treatment at the earliest possible point. I’ll also help you assess the disease’s severity, explain the different stages of treatment, and give you tips on how to prevent heaves in the first place.

Like Asthma
Heaves is an allergic-based disease that compromises your horse’s ability to breathe, similar to the way asthma affects humans. When your horse is exposed to allergy-producing substances in the air, such as dust and pollens, cells in his lungs react by releasing chemicals that cause air-passage linings to swell, thicken, and produce mucus. When he breathes, air gets trapped within these thickened passages. He then must use extra effort to expel this trapped air. The more your horse is exposed to allergens, the more sensitized his lungs become. The disease is most common among mature and older horses.

As the disease progresses, your horse’s airways become ever thicker. More mucus is produced. He begins to cough as he struggles to exhale. Thick mucus appears in his nostrils, and he begins to labor with every breath. Bacteria can become trapped in his airways, leading to a bacterial infection (such as pneumonia), a common complication in advanced cases of heaves.

Symptom Checklist
If your horse has two or more of the following signs of the disease, it’s time to call your vet for a definitive diagnosis and treatment plan.

Increased Respiratory Rate

  • Why it happens: Your horse is having difficulty expelling air through his thickened airways, so he breathes faster than normal at rest in an effort to get enough oxygen. His respiratory rate will also likely be elevated more than normal after exercise.
  • How to ID it: Count your horse’s breaths per minute at rest by watching his sides move in and out as he breathes. His normal respiratory rate at rest should be between 8 and 16 breaths per minute; if it’s higher, suspect a problem.

Increased Abdominal Breathing Effort

  • Why it happens: Your horse is forced to use his abdominal muscles to push air out of his lungs because his normal breathing muscles aren’t strong enough to do the now-bigger job.
  • How to ID it: As your horse breathes, watch for abnormal abdominal-muscle action around the belly near the flank. (Compare what you see with the breathing effort of other nearby horses.) Also note the appearance of the muscles on the sides of his belly?do they seem enlarged compared to those of other horses? This could be a heave line, a horizontal run of muscle development caused by his extra breathing effort. Look for it about threequarters of the way down from his spine, toward his belly.


  • Why it happens: His lung tissues are irritated from airborne allergens, and he’s trying to expel mucus.
  • How to ID it: Heaves-related coughing typically occurs at the beginning of exercise, plus during feeding and stallcleaning time when dust is in the air. Coughing continuously throughout the day might also indicate heaves. (Note: A cough accompanied by a fever could be due to a bacterial respiratory infection, but that doesn’t necessarily rule out heaves. Your horse could be feverish because he has a heaves-related, fever-producing illness, or a completely separate but concurrent disease that causes a fever.)

Nasal Discharge

  • Why it happens: Lung cells produce mucus as part of the allergic response that’s associated with heaves. (How quickly they do so depends on how quickly the disease is progressing.) Mucus that builds up inside your horse’s lungs eventually passes down the airways and appears in his nose.
  • How to ID it: Watch for a thick, cloudy discharge that builds up in your horse’s nostrils. (Note: Although a gunky discharge can occur simply as a result of inflammation from your horse’s heaves, it can also indicate the presence of a complicating bacterial infection. Your vet might obtain a sample from your horse’s airway to determine whether the mucus consists only of inflammatory cells, or if bacteria are also present.)

Abnormal Lung Sounds

  • Why it happens: The effort to force air out through narrowed air passages results in wheezing.
  • How to ID it: This is usually best left to your vet, who’s trained to recognize and distinguish breathing irregularities using a stethoscope. If your horse’s condition is quite severe, however, you might be able to detect wheezing if you listen carefully. If his case is less advanced, you might be able to hear wheezing when he breathes hard during exercise. (Note: Don’t confuse lung sounds with throat sounds, such as roaring, which can be caused by an obstruction or by paralysis of the larynx.)

Weight Loss

  • Why it happens: Your horse is expending extra effort breathing, plus his body could be depleted of oxygen.
  • How to ID it: Evaluate the muscle and fat layer covering his ribs, spine, and hips. If the underlying skeletal structures become more prominent, your horse is losing weight. (Tip: To monitor your horse’s weight, consider checking him monthly using a weight tape.)

Treatments for Heaves

Once your vet has confirmed your suspicion that your horse has heaves, plus determined whether the case is mild, moderate, or severe (see “How Bad Is It?,” opposite page), he or she will recommend a treatment plan. To help you understand the available options, I’ve outlined the typical treatments.

Stage 1 Treatment: Mild Heaves
You’ve caught the condition early and might even have a chance to halt its progress. Treatment will consist simply of limiting your horse’s exposure to allergy-producing dust and other particulates. (Note: Keep up these Stage 1 treatments even if your horse is also undergoing those in Stage 2 or 3. These management measures are the most important actions you can take to protect his lungs.)

  • Turn him out as much as possible. Being in open, fresh-air areas will limit his exposure to common barn dust and other airborne particles that can worsen his condition.
  • Provide good ventilation inside. If your horse must stay mostly in the barn, put him in a stall at the end of the aisle where there’s good airflow, and leave doors and windows open as much as possible. When hauling, make sure the trailer is well-ventilated and clean of bedding that might fly around (rubber mats can provide needed cushioning).
  • Feed him ?chest-high.’ Placing feed on the ground ups your horse’s exposure to dust, while feeding from a hay bag or rack placed above his withers can promote the inhalation of hay and dust particles. A chest-high feeder avoids both these scenarios.
  • Wet his hay. Sprinkling it liberally with water or even soaking it just before feeding cuts down the dust.
  • Consider pellets instead. If moistened hay fed at the correct level doesn’t bring improvements in your horse’s condition, consider feeding a pelleted forage ration, possibly moistened, instead.
  • Moisten his bedding. Spray a fine mist of water over the surface of his stall every time you clean it (ideally once or even twice daily). Avoid the dustiest beddings, such as wood shavings. Shredded-paper beddings might be a good option.
  • Don’t clean around’ him. Stall-cleaning stirs up particulates, so remove your horse before cleaning his stall.
  • Avoid dusty and/or indoor arenas. Ride outside or in a well-watered arena. When trail riding, go in front to avoid “eating the dust” of others.

Stage 2 Treatment: Moderate Heaves
If your horse is showing moderate signs of heaves, or if there’s no improvement in his mild signs with Stage 1 treatments in place, your vet could recommend one or more of the following treatments. (Note: If you show, consult your association’s rulebook to determine whether any of the following substances are currently banned.)

  • Oral corticosteroids. These will help control the inflammation of the airways that occurs in response to allergy-producing substances. This, in turn, reduces airway thickening and mucus production. Two commonly used oral corticosteroids are dexamethasone and prednisone.
    Dexamethasone is the most potent and therefore the most effective, but also has a higher risk of side effects, including founder. Your vet might recommend it as an initial treatment to get your horse’s symptoms under control. Prednisone is less potent but safer; it’s more likely to be recommended for long-term use, often after treatment’s been started with dexamethasone.
  • Oral bronchodilators. These medications help relax the muscles that cause your horse’s air passages to spasm and close; this, in turn, helps dilate and open airways to make breathing easier. Clenbuterol is an effective oral bronchodilator.
  • Expectorants. These break down and thin mucus, making it easier for your horse to expel it from his lungs. This clears the way for more normal breathing, plus helps eliminate bacteria that could be trapped in the lungs. There are a variety of over-the-counter expectorants, such as Tri-Hist? or Spec-Tuss, available from your feed store or your vet. In more serious cases, your vet might prescribe potassium iodide, a strong, highly effective expectorant. Make sure your horse also has plenty of fresh, clean water, which helps to loosen secretions naturally.
  • Antibiotics. These might be needed if a bacterial infection is complicating your horse’s heaves. Ideally, your vet will collect a sample from your horse’s airways in order to target the specific organism with the most appropriate antibiotic. (Tip: Oral feed supplements marketed to help horses with respiratory problems could also be beneficial. Ask your vet if he or she would recommend one.)

Stage 3 Treatment: Severe Heaves
If your horse is showing signs of severe heaves and/or hasn’t improved with either Stage 1 or Stage 2 treatments, your vet might recommend inhaled medications. You’ll place a specially designed mask (such as the Aeromask, by Trudell Medical International) over your horse’s nose several times a day to deliver medication directly to his lungs for maximum effect. This allows lower doses of drugs to be effective, thus lessening the risks of side effects. (Note: Your vet might also recommend expectorants and antibiotics, as in Stage 2 heaves.)

  • Inhaled corticosteriods. Like their oral counterparts, these medications help control inflammation and reduce airway thickening and mucus production.
  • Inhaled bronchodilators. Like their oral counterparts, these drugs help open your horse’s airways. Your vet will recommend that you administer the bronchodilator first, then wait a period of time for your horse’s airways to open before administering the corticosteroid. That way, the latter can reach as deeply into your horse’s lungs as possible for maximum effect.

What’s in a Name?

Classic heaves, once referred to as COPD (chronic obstructive pulmonary disease), is now more accurately being called RAO, or recurrent airway obstruction. This distinction has been made because of the underlying disease process reactions of the tissues within the small airways in the lungs result in breathing difficulties.

A less-severe respiratory problem, IAD, or inflammatory airway disease, was once thought to be an early form of heaves but has now been identified as a separate entity.

In IAD, accumulations of mucus and inflammatory cells are found in the trachea. Horses with IAD typically don’t show respiratory distress at rest, but their performance could be impaired, and they might take longer to recover after exercise. They generally don’t have a nasal discharge and might not even have a cough.

Unlike heaves, which tends to involve mature or older horses, IAD is more common in young performance horses. Its cause is unknown, though some experts believe one factor could be the inhalation of dust, mold, and bacteria. In racehorses, there’s evidence IAD is associated with recurrent bacterial infections, particularly those involving the Streptococcus bacterium.

The connection between IAD and heaves is currently unknown, though treatments and preventive measures are similar.

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