Horses that live in barns, stables or outdoors are typically exposed to high levels of pollens, molds and other particulates. As such, they have an increased risk of developing a chronic and debilitating respiratory syndrome, often known as heaves, or recurrent airway obstruction (RAO). While these terms fall under the umbrella of “equine asthma,” RAO is a performance-limiting, respiratory disease that affects horses with long-term exposure or excessive sensitivity to particulates. This is distinguished from the less severe form of equine asthma, known as Inflammatory Airway Disease (IAD). This is a much more common and potentially curable malady.1 Conversely, RAO can often be effectively treated, but is not said to be curable. Evidence suggests that RAO is the result of the lung's hypersensitivity to inhaled antigens, although multiple theories exist regarding why it occurs.

The determining clinical sign distinguishing RAO from IAD is clearly recognizable episodes of respiratory distress. In this case, a horse appears to be heaving with the effort to breathe; these episodes are usually transitory until the horse becomes severely affected.    The most common clinical signs of RAO are chronic cough, nasal discharge, exercise intolerance, and respiratory difficulty. Horses with RAO often appear normal at rest, but can have an increased respiratory rate and/or cough. Due to this syndrome, a “heave line” can frequently be seen along the bottom edge of the ribs, caused abdominal muscles which enlarge due to the excess work associated with breathing.

Types of Recurrent Airway Obstruction

There are two different forms of RAO. The first is the type associated with stalled horses; the second is summer pasture-associated recurrent airway obstruction (SPARAO).1 The latter is most commonly seen in horses that live on pasture and come in contact with high levels of airborne mold spores. Winter is usually the most common season for heightened symptoms of barn-associated RAO in the northern U.S., while the most prevalent signs of pasture-associated heaves happen in the Spring and early Winter in the north, and in summer and early fall in the south.

Diagnosis of RAO

A diagnosis of RAO is usually made based on history, management conditions and clinical signs. Diagnostic tests to confirm RAO include bronchoalveolar lavage, lung function testing, and chest radiographs in selected cases. Upper airway endoscopy is sometimes performed in conjunction with these tests to help rule out upper airway causes of chronic cough.

Once confirmed, horses with barn-associated RAO should be kept on pasture whenever possible, with fresh grass as the source of roughage supplemented with pelleted feed. Round hay bales are highly allergenic and should not be fed. Horses with SPARAO should not be stalled in the same structure.1 Hay should be stored in a different structure, and straw or other dusty bedding should not be used.

Treatment of RAO

Corticosteroids and aerosolized bronchodilators are among the most efficacious therapies for horses in respiratory distress. Intravenous administration of dexamethasone often improves lung function within one to two hours of administration. Dexamethasone may be continued for one to several weeks. For horses less severely affected cases of RAO, prednisolone is a less potent drug that may have fewer side effects.1

Albuterol is contraindicated in horses that are hypersensitive to it or to other sympathomimetics. Most side effects are dose-related and are consistent with other sympathomimetic agents.

Where to buy Albuterol

Albuterol is available in the U.S. through several pharmaceutical manufacturers and through veterinary custom compounding companies. 

FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.

1Derksen FJ, Olszewski MA, Robinson NE, Berney C, Hakala JE, Matson CJ, Ruth DT. Aerosolized albuterol sulfate used as a bronchodilator in horses with recurrent airway obstruction. Am J Vet Res. 1999 Jun; 60(6): 689-93.