Thank you, from all of us at Rocky Bay Equine!

Throughout the last year, we've treated several horses with inflammatory airway disease (IAD).  Typical clinical signs of IAD include exercise intolerance, poor performance, and/or coughing.  A clear to white nasal discharge may also be present intermittently.  At the severe end of the spectrum, a horse may exhibit actual airway obstruction, also called heaves, where respiratory distress is present when the horse is standing still without being prompted by exercise.  

Inflammatory airway disease may affect horses that are stabled in areas where they are exposed to large amounts of particulates in the air.  For instance dusty hay or straw stored overhead, or where stalls are located immediately adjacent to and under the same roof as an indoor arena.  Horses are obligate nasal breathers, meaning they only breathe through their nose and their upper respiratory tract is designed with several filtering mechanisms. However, very small particles can still reach the lower airways.  When these tiny particles enter the small airways and air sacs (alveoli) of the lungs, they stimulate the body's inflammatory response causing cells like eosinophils, T-cells and macrophages, to migrate to the lungs.  These cells stimulate mucus secretion, which helps the body's defense system entrap the particulate debris (dust, pollen etc) and escort it out of the respiratory tract.  The addition of mucus, combined with the original particulates may exacerbate the cough reflex, which is a good thing when it helps move debris out of the airway, but it can sometimes be a not so good thing if it creates a cycle of continued irritation within the lower airway.  

Other possible causes of coughing, poor performance and nasal discharge such as: viral infections, bacterial or fungal pneumonia, cancer, and lungworm infestation need to be ruled out before a diagnosis of IAD is confirmed.  We accomplish this by beginning with a thorough physical exam.  A re-breathing test is performed by having the horse “re”-breathe their expired carbon dioxide into a bag, causing them to take large breaths.  The deep breathing enables us to listen with a stethoscope for wheezing or crackling sounds, which indicate specific processes going on within the lungs.  Typically in a horse with IAD we will hear wheezes, whereas crackling sounds may suggest pneumonia.  A complete blood count and fecal are submitted to rule out systemic infection and the presence of parasites.  (Did you know that parasites can also cause lung disease?)  A broncheolalveolar lavage (BAL) may  be performed to identify the types of cells present in the lungs, which confirms the inflammatory process and helps rule in or out the additional complication of infection.   Treatment of IAD is highly dependent on environmental management.  While it's not always possible to create the perfect environment, now that you know in general how IAD works, use the following list to start thinking about how you can improve the situation for your own horse. 

• Use low-dust bedding. Avoid straw and sawdust, which can promote a dusty environment. Instead, try lower-dust wood shavings.
• Minimize atmospheric dust and enhance ventilation. Keep arena footing dampened to reduce dust if horses are stabled near by.  Poor ventilation promotes IAD and you may need to relocate a horse suffering from this disease.
  
• Plan chores around turnout schedules. Put sensitive horses outside while you’re working in the barn since excess dust and particles fill the air during stall cleaning and aisle sweeping.
• Avoid feeding dusty hay. Instead, try feeding chopped forages or a pelleted complete feed. If hay is a necessity, soak it to reduce the amount of dust it contains and / or feed it in a large open bucket on the ground rather than in a hay net.
  
• Embrace turnout. Horses with IAD benefit from being outside away from dusty environments for as much of the day as possible.
• While traveling avoid tying your horses' heads up, or allow for frequent stops to let them lower their head to cough out collected debris.
  

Making environmental changes is important for treatment of this disease, in addition, the horse may be placed on a tapering dose of corticosteroids or on an anti-inflammatory regimen such as oral flunixin meglamine (Banamine).  For performance horses, inhaled corticosteroids may also be an option for addressing inflammation in the lower respiratory tract.   It's not always a quick or easy fix, but with optimal treatment, many horses can break the cycle of irritation that induces the annoying and debilitating chronic cough and intermittent nasal discharge.  Please call us if you have any questions or concerns regarding cough, nasal discharge and/or exercise intolerance in your horse.