Veterinary advice should be sought before applying any treatment or vaccine.


Equine Asthma Syndrome, Recurrent Airway Obstruction, COPD

Heaves, also known as recurrent airway obstruction (RAO), is a chronic inflammatory disease that causes respiratory problems in mainly older horses. The disease was previously referred to as COPD, for it was originally thought to resemble COPD in humans, however more recent research indicates that it actually more closely resembles human asthma. The American College of Veterinary Internal Medicine (ACVIM) have recently lumped heaves, inflammatory airway disease (IAD), and summer pasture-associated obstructive pulmonary disease (SPAOPD) together under the term, "equine asthma syndrome." Horses with heaves suffer from chronic coughing and nasal discharge, and/or difficulty exercising or breathing. The disease is typically associated with narrowing and spasms of the air passages (bronchoconstriction and bronchospasm) and excessive mucus production.

The severity of airway obstruction, inflammation, and associated symptoms can vary widely among horses. Recent studies confirmed that the plasma cortisol concentration in the horse increases concurrently with the development of acute exacerbation of RAO. In RAO, haptoglobin is a marker of both acute and chronic systemic inflammation, whereas high concentrations of SAA indicate acute inflammation.

Risk Factors

Risk factors are similar to those seen in humans with asthma, which include indoor and outdoor allergens (mites, pollens, dust, endotoxins, mold spores, mycotoxins) and irritants like lipopolysaccharides (LPS). Horses with RAO tend to be extra sensitive to exposure of dust and molds commonly found in stored hay. Noxious fumes and high humidity can also act as triggers.

How Heaves is Diagnosed

Heaves is diagnosed through thoracic radiographs, BAL (bronchoalveolar lavage) with cytology, CBC and/or blood chemistry.

Treatment Options

There is no cure for heaves. Treatment goals are aimed at improving lung function and inducing clinical remission. Treatment options include corticosteroids, bronchodilators, and decreased antigen exposure (reduced exposure to dust from barn conditions, feed, bedding, and stored hay). Antihistamines may also be of benefit but have shown not to be as effective for long-term control in some horses.


Wheezing, crackles, or tracheal rattles
Respiratory distress
Severe coughing (especially when exercised)
Nasal discharge
Flared nostrils
Weight loss
Exercise intolerance
Abnormal or difficulty breathing at rest
Abdominal heave line


  • History
  • Clinical signs
  • Physical exam
  • Bronchoalveolar lavage fluid (BALF)
  • Endoscopy
  • Ultrasound
  • Radiographs



Management changes (minimize exposure to dust)Wetting hay (different then soaking), switch to low-dust feed, increase pasture turnout, switch to low-dust bedding, maximize air flow through barn and ventilation
Corticosteroids (given orally)Prednisolone, Dexamethasone
BronochodilatorsInhaled albuterol, Buscopan, Clenbuterol
Nasal oxygen
Omega-3 fatty acidsFeeding supplemental omega-3 fatty acids helps reduce symptoms


  • Reduce exposure to dust and molds and time spent in the stall.
  • Use a low dust bedding material
  • Maximize turnout outside
  • Feed square hay bales instead of round hay bales
  • Don't sweep barn aisles while horses are inside
  • Design barns with good ventilation
  • Regularly test air quality levels in barns
  • Never feed moldy hay to horses


Good if changes in management occur and the horse is less exposed to dusty environments

Scientific Research

General Overviews

Clinical Trials

  • Flaring nostrils icon

Age Range

It is most frequently seen in middle-aged to older adult horses (age 7 and older).

Risk Factors

  • Horses with little to no turnout
  • Dusty barns
  • Sweeping or blowing out barn aisles while horses are inside
  • Horses with prior history of a respiratory infection early in life
  • Feeding round bales to horses
  • Warmblood or Lipizzaner horse breeds have a genetic predisposition