Lower respiratory tract disease in horses: Part 2

By Lauren Lamb

Last month we talked about lower respiratory tract disease in horses as it pertains to infectious pneumonia (bacterial, viral and parasites). This article expands on lower respiratory tract disease in horses by focusing on some of the more common non-infectious lower airway inflammatory diseases.

Recurrent airway obstruction (RAO) and inflammatory airway disease (IAD) are the most common types of inflammatory airway disease seen in horse. Both of these diseases have a similar clinical presentation, but treatment and management can differ depending on the disease.

The cause of RAO and IAD is secondary to inhalation of various irritants and allergens. The main irritants are dust found in the bedding and hay and the ammonia released into the air from the horse’s urine. If the horse’s stall is not cleaned regularly, the ammonia from the urine will begin to accumulate in the air and cause inflammation of the horse’s lower airway.

Recurrent airway obstruction, also known as COPD or heaves, is a disease caused by chronic lower respiratory tract inflammation. The disease is often incorrectly compared to COPD in humans. Current research shows that RAO is more similar to human asthma rather than COPD. Like human asthma, RAO is characterized my recurrent bouts of reversible narrowing and inflammation of the bronchioles—the last part of the airway that lead to the alveoli. The bronchiole is a small tube of muscle that can dilate and contract. Inflammation of the bronchiole will cause the muscle to contract and restricted air flow in and out of the alveoli.

To learn more about respiratory disease in horses, read the September issue of OKFR!