What is IAD?

Inflammatory Airway Disease (IAD) is a chronic inflammatory condition that affects the lower airways of young horses. IAD is characterized by chronic cough, excess mucus in the trachea, and mild exercise intolerance. If a horse coughs several times at the beginning of exercise, it may have upper airway irritation, tracheal irritation, allergies, or IAD. Horses with IAD have normal attitudes, appetites, and temperatures. They also do not exhibit any increased respiratory effort at rest. Inflammation and mild airway obstructions caused by mucus occur in the bronchi and bronchioles, resulting in bronchitis and bronchiolitis. It is often caused by substances that irritate the airways such as mold, dust, noxious gases, or pollutants.

How is IAD diagnosed?

Although a horse coughing does not sound serious, diagnosing the reason for the cough and addressing the cough with a specific treatment is advised. A general physical examination with attention to the respiratory system may show some clear or white discharge present in the nostrils. Listening to the lungs and trachea may reveal harsh sounds such as crackles, or wheezes, suggesting the presence of mucus and/or fluid. When the horses’ lungs sound quiet, a rebreathing bag exam is performed. A bag is placed over the horse’s muzzle, making it only be able to breathe the air present in the bag, for a short time. This makes the horse breathe slowly and deeply, accentuating any sounds present in the lungs and/or trachea. If any abnormal sounds from the lungs or trachea are identified, an endoscopic examination of the airways is recommended. The structure and functionality of the upper and lower airways are evaluated and the presence of mucus or other abnormalities is identified. If any mucus is seen in the trachea, a bronchoalveolar lavage (BAL) can be performed to diagnose IAD. A long thin tube is passed through the horse’s nose into the trachea, primary bronchi, and into the lower airways. The BAL is performed with a saline solution that is washed into the airways and recovered with a sample of cells, mucus, and any contaminants that may be present. The sample is then delivered to the lab and a cytologic examination is performed to evaluate the contents.

How can IAD be prevented or treated?

When horses cough, it is a common clinical sign that the horse has a respiratory condition. The best way to prevent a horse from contracting IAD is to improve the ventilation and decrease the dust in the horse’s environment. This can be accomplished by turnout, having stalls with windows, sealing where the hay is stored, wetting or soaking the hay fed to the horse, and switching or supplementing the diet with forages. Changes in the environment or feed and/or medication can be prescribed to the horse depending on the results of both the endoscopic examination BAL. Antitussive (cough) medications, systemic steroids, inhaled steroids, bronchodilators, and mast cell stabilizers may be prescribed.


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