Equine Respiratory Allergies - Heaves

The respiratory illness commonly known as “heaves” or “broken wind” was, until recently, referred to as Chronic Obstructive Pulmonary Disease (COPD) in the medical community. It has been renamed Recurrent Airway Obstruction (RAO) to indicate that it is not the same condition as the COPD found in humans.  Affecting mostly older horses, heaves arises when lung cells react to allergens by swelling and thickening air passage linings and increasing mucus secretions. If thickened airways trap enough bacteria, the horse could develop pneumonia or other respiratory infections.

RAO is an episodic disease triggered by exposure to

• moldy, dusty or poorly-cured feed
• long-term confinement to a stable environment
• inadequate or absent stable ventilation
• dust
• pollen

The exact cause of the disease is not known, but research suggests that the characteristic inflammation of the small airways results from an allergic response to dust, mold, or other trigger factors.

Symptoms of RAO include:

• nasal discharge
• chronic coughing which may or may not produce mucous
• flared nostrils in the resting state
• labored breathing with elevated respiratory rate
• exercise avoidance
• increased abdominal movement during breathing
• depression

RAO is diagnosed through history (especially of recurrent coughing episodes), physical examination, and blood work.  In particularly difficult or ongoing cases, successful diagnosis may include radiography, endoscopy, bronchoalveolar lavage (BAL), and pulmonary function testing.

Treatment

Commonly, treatment of Heaves requires management and changes in diet and environment;  a clinician may also prescribe medications. The main goal is to reduce a horse's exposure to organic dust. Hay should be thoroughly soaked or replaced with a dust-free source of fiber, and horses should be kept outdoors as much as possible. Horses with RAO often improve dramatically when removed entirely from an indoor barn or stable environment. Dusty riding rings can also trigger episodes and should be avoided. Corticosteroids may be prescribed to reduce inflammation, and bronchodilators may be given to relieve spasms in the airways. Properly managed, horses with RAO can lead normal lives; but they may remain permanently sensitive to various trigger factors.

Researchers are only just beginning to understand how equine allergies work and how they differ from those occurring in other species. The hope is that someday even the most sever equine allergy will be fully treatable, and a thing of the past.