Recurrent Airway Obstruction (Heaves)

By: Katie Jones, CVT­

With pastures dwindling this time of year, the quality of grass has diminished significantly; therefore, many of our horses are turning to round bales to fulfill their forage needs. With their heads buried into these dusty bales several respiratory problems can arise. Horses can go years without any problems, while others tend to have repeated respiratory problems. One of the most common causes of respiratory distress in horses is Recurrent Airway Obstruction (RAO).

horseinroundbale_0Recurrent Airway Obstruction, better known as Heaves, is an allergic response associated with inflammation and obstructive airway disease. In humans, this condition is similar to asthma. RAO is initiated by the inhalation of organic dusts (hay and bedding) that contain allergens, endotoxins, molds, and other small particles and substances that trigger inflammation in the lungs. Not all horses respond the same way to the stimulants; the age of the horse and their genetic disposition both appear to trigger negative responses. Horses prone to “heave episodes” can even react to the dust commonly found in good quality hay; it is not just an indicator of bad hay.

A heaves episode is ultimately triggered by exposure to the allergens listed above. However, when a horse most consistently living on pasture is brought into a stable for feeding they can show symptoms as soon as 6-8 hours after being brought in. RAO results from the horse developing bronchospasm (narrowing of airway) and mucus accumulation which can lead to remodeling of the airway wall. Remodeling to the airway will cause a permanent increase in the thickness of the walls, which decreases the elasticity of the lungs therefore affecting the horse’s ability to breath.

Horses experiencing a mild episode of heaves usually exhibit coughing associated with fig3 tracheaexercise, feeding, or airborne dust when the barn is swept. Sever episodes of heaves will appear as respiratory distress; an increased intolerance to exercise, flared nostrils, labored breathing, and occasionally nasal discharge. In most cases, a consistent history and a basic physical exam will provide enough information for a ROA diagnosis. A branchoalveolar lavage (BAL) can also be performed for more specific, in-depth information. To preform a BAL the doctor will “flush” the lungs with saline using a long tube inserted through their nostril. This flush will pick up fungal elements, white blood cells, or pneumonitis indicators. If the BAL confirms the presence of neutrophilic inflammation, it not only confirms the horse has a lower airway inflammation but the test can differentiate the cause of the inflammation.IMG_20151116_130359344

Treatment for horses suffering from unresolved chronic RAO includes a handful of medication options.   The main drugs used are corticosteroids (dexamethasone, prednisolone, or fluticasone) which work to reduce the inflammation in the lower airways, and bronchodilators (clenbuterol or albuterol) which relieve airway obstruction by dilating the airways. To help manage mild RAO cases, Anoka Equine is offering a new product called Heave Relieve.

Recurrent Airway Obstruction is a manageable condition. For horses showing signs, it is best to have the horse seen by your local veterinarian to prevent chronic damage. Many horses will only require a change in environment to manage their episodes. Consult with your local veterinarian for a complete diagnosis and the best treatment plan for your horse.