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Equine Asthma

Information obtained from Boehringer Ingelheim


Equine asthma is an umbrella term encompassing inflammatory diseases of lower airways in horses, formerly known as heaves and inflammatory airway disease. It is categorized into mild to moderate equine asthma which affects horses of any age, and severe equine asthma which is typically seen in horses older than 7 years of age. Studies show that up to 80 percent of horses in different populations may suffer from mild to moderate equine asthma2, while severe equine asthma may affect as many as 11-17% of horses. Equine asthma can have a significant impact on a horse’s performance and quality of life. Over time severely asthmatic horses may develop changes in the lung, which makes it difficult to breathe, even at rest. So how can owners detect equine asthma early to help prevent the disease from getting worse?

Equine asthma is caused by exposure to high concentrations of organic dust, especially the dust particles that are small enough to pass with inhaled air to the lower airways. Such particles are commonly found in hay and bedding. A subtype of severe equine asthma called summer pasture asthma is found in horses kept outside during grazing seasons, where pollens and air pollution as well as heat and humidity play a role in disease exacerbation.  

The key principles of treatment of equine asthma include 3 steps:

  1. Removal of triggering factors through environmental modification

  2. Addressing inflammation in the lung with corticosteroid therapy

  3. Use of bronchodilators as necessary for fast relief of bronchospasm 


Graphic by Boehringer Ingelheim

Be it a mild to moderate or severe case of equine asthma, the first thing to do when your horse is afflicted is to decrease exposure to triggering environmental factors. Decreasing dust exposure from hay and bedding is a key. This can be achieved by  feeding low dust options such as hay pellets or steamed hay, and by using  wood shavings instead of straw for bedding. Another option is to increase the turnout time so that the horse is outside, away from the dust of the stable area. Horses with pasture associated asthma will benefit from living inside well-ventilated, clean and low-dust stables. 

The cornerstone of medical therapy is to use anti-inflammatories to decrease the inflammation of the lower airways. This is best achieved by administration of potent glucocorticosteroids delivered directly to the lung  by inhalation. In certain cases, there may also be a need for bronchodilators in addition to environmental changes and cortisocteroid therapy. 

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