Lower airway inflammation is common in horses. Even though the problem is easily recognized, many questions remain about the underlying disease mechanisms leading to lung inflammation. The clinical findings, disease severity, response to treatment, and rate of recurrence can vary significantly between horses. A better understanding of the biological processes resulting in lung inflammation will be essential in guiding the treatment and establishing a prognosis for our patients.
Currently, the syndrome of lower airway inflammation in horses includes recurrent airway obstruction (heaves) and inflammatory airway disease (IAD). Horses with heaves tend to be older and have more obvious signs of respiratory disease. Signs of respiratory disease can include coughing, nasal discharge, and exercise intolerance. Horses with heaves can have a pronounced breathing effort at rest. In some cases, decreased performance may be the only clinical sign.
Heaves is a chronic problem with recurring acute episodes of respiratory signs such as coughing and increased breathing effort. The inflammation in the airway is thought to be the result of an allergic response to organic dust and mould. This is why environmental management is one of the mainstays of treatment of horses with heaves. Corticosteroids are often used initially to reduce inflammation during acute episodes. Another type of medication which is commonly administered are bronchodilators which help to open up the horse’s airway.
Inflammatory airway disease is less well understood. It tends to occur more commonly in younger horses and clinical signs are typically less pronounced when compared to heaves. Similarly to heaves, horses with IAD have lung inflammation, but it is usually less severe. Different types of inflammatory cells can be present in individual animals, which means that the biological mechanisms resulting in inflammation may not be the same in all cases of IAD. The cause of lung inflammation in IAD is not known and may include one or more of the following: bacteria, viruses, organic dust and mould.
Dr. Julia Montgomery is board certified in large animal internal medicine and holds a PhD from the Atlantic Veterinary College, University of Prince Edward Island. Dr. Montgomery’s research interests include equine immunology, specifically innate immune mechanisms involved in non-septic lower airway inflammation in horses and remote (secondary) lung injury in horses and dogs. Dr. Montgomery is an Assistant Professor in the Department of Large Animal Clinical Sciences and a member of the Pulmonary Pathobiology Laboratory in the Department of Veterinary Biomedical Sciences at Western College of Veterinary Medicine, University of Saskatchewan.
Dr. Katharina Lohmann is board certified in large animal internal medicine and holds a PhD from the University of Georgia, USA. Dr. Lohmann’s current research interests include equine endotoxemia, tick-borne diseases, and airway diseases in horses. Dr. Lohmann is an Associate Professor in the Department of Large Animal Clinical Sciences where she combines clinical service, teaching and research.