Respiratory

Equine asthma is an umbrella term that encompasses mild-moderate disease (formerly inflammatory airway disease) and severe disease (formerly recurrent airway obstruction or heaves). Classification is based on clinical severity, BAL cytology, and response to environmental and pharmacologic management.

Diagnosis relies on bronchoalveolar lavage cytology showing increased neutrophils, eosinophils, or mast cells in a horse with subtle signs such as poor performance, intermittent cough, or excess tracheal mucus. Endoscopy and tracheal wash may also support the evaluation.

Maximizing ventilation, minimizing dust and mold exposure, using low-dust bedding, soaking or steaming hay, and increasing turnout are foundational. Environmental management alone can resolve many cases of mild-moderate equine asthma.

Inhaled corticosteroids and bronchodilators are used in horses with moderate to severe equine asthma when environmental changes alone are insufficient. Delivery systems adapted for equine use allow targeted lower airway treatment with reduced systemic side effects.

EIPH occurs when high pulmonary capillary pressures during intense exercise cause rupture of pulmonary capillaries and bleeding into the airways. It is detected endoscopically in up to 75% of Thoroughbred racehorses after intense exercise and also affects sport horses. Diagnosis relies on post-exercise endoscopy or BAL, and management may include furosemide where permitted by regulatory guidelines.

Infectious respiratory disease is caused by viral or bacterial pathogens such as equine influenza, EHV, and Streptococcus equi, typically presenting with fever, nasal discharge, and lymph node enlargement. Equine asthma is non-infectious and allergen-mediated, requiring different diagnostic and management approaches.