Recurrent Airway Obstruction (RAO) in Horses

Causes Treatment and Prevention
Horses have delicate lungs and are very sensitive to inhaled dust pollen and mold spores. Exposure to these irritants over time can lead to a persistent cough difficulty breathing and nasal discharge. This allergic response is called recurrent airway obstruction RAO. Older terms still often used for this condition include chronic obstructive pulmonary disease COPD heaves or broken wind.
RAO usually first appears when the horse is between nine and 12 years of age. Approximately 12 percent of mature horses have some degree of this respiratory affliction 1

Although RAO is a chronic condition many horses afflicted with this respiratory problem enjoy long and relatively normal lives. However management of these horses does require vigilance to ensure the horse isnt overworked or exposed to allergens that trigger breathing difficulties such as dusty hay. While theres no cure most horses with heaves can be comfortable and can be lightly worked. Heres how recurrent airway obstruction develops and what you can do to help your horse.
What Is Recurrent Airway Obstruction?
Horses lower respiratory systems as well as the respiratory systems of other mammals consist of a large trachea windpipe that branches off into two main bronchithese are something like the stems of the lungswhich then branch further into small airways called bronchioles. Recurrent airway obstruction is an allergic response that causes inflammation in the bronchioles. Over time this causes them to thicken and leak mucus leading to the characteristic cough difficulty breathing and other symptoms of this chronic condition. RAO is considered to be a type of equine asthma 2
While the mechanisms of RAO are not well understood it is ultimately believed to be caused by the horses lungs hypersensitivity to allergens especially hay straw mold and dust. Horses that live in stables and eat hay are the likeliest to develop the condition but it can strike pastured horses as well. Typically stabled horses with RAO have the worst symptoms in the winter and spring while pastured horses suffer the worst symptoms in the summer or early fall 2
Symptoms of RAO in Horses
In the early stages of RAO or in horses only mildly afflicted with the disorder the symptoms are generally just a slightly runny nose and dry cough. As the disease progresses however symptoms generally become far more severe.
Symptoms
Chronic cough which may bring up secretions
Nasal dischargerunny nose
Labored breathing
Exercise intolerance
Heave line of overdeveloped chest muscles at the bottom of the rib cage due to the