Equine Asthma and Recurrent Airway Obstruction are one of the most common causes of coughing
and nasal discharge diagnosed in stabled horses.
It is non-infectious, non-contagious and environmentally induced and occurs when the horse develops an allergy to spores that it has inhaled, and is usually but not exclusively seen in stabled horses.
What Is Equine Asthma?
Previously it was often referred to as COPD (Chronic Obstructive Pulmonary Disorder), however Recurrent Airway Obstruction or Equine Asthma is now considered a more accurate description of the symptoms.
It is an inflammatory disease of the smaller airways (bronchioles and alveoli) caused by an allergic reaction, often to tiny dust particles and spores. This reaction in the airways results in production of fluid, and thickening of the small airways, causing them to become obstructed.
To compensate for this, the horse has to make an increased effort to breathe, and often develops a cough to clear trapped mucus. Unfortunately it is often a progressive condition, and whilst there is no ‘cure’, steps can be taken to manage the condition, allowing your horse to accommodate to it.
What Are The Symptoms?
- Nasal discharge
- Frequent cough
- Exercise intolerance
- Increased respiratory rate and effort
- Development of a ‘heave line’ (due to increased respiratory effort using chest and abdominal muscles)
- Acute attacks of respiratory distress due to repeated exposure to dust or pollens
How Is It Diagnosed?
Usually a diagnosis is based on clinical examination, history of exposure to dust, pollens or fungal spores, and examination of management conditions.
In many cases it is necessary to perform an endoscopic examination to allow collection of bronchiolar or tracheal fluid to distinguish between Equine Asthma and other respiratory conditions, such as chronic infection. This allows us to implement the appropriate treatment needed for the diagnosed condition, as this can vary significantly. For example the correct treatment for Equine Asthma could make the horse very unwell if there was also an established respiratory infection, so it is vital to know exactly what we are dealing with before we start treatment.
Nevertheless it is important to remember that infection can commonly occur alongside and secondary to Equine Asthma.
How Do You Treat Equine Asthma?
Many cases will respond to changes in management alone if caught early. This involves removing the cause of the allergy (whether this is dust, pollen or fungal spores). In general, affected horses should be kept on a ‘dust free’ management system, designed to keep environmental allergens to the minimum.
Changing bedding from straw to shavings, paper or other non-organic material can help, as well as keeping the bed scrupulously clean. Hay should be soaked before being fed, or haylage could be used and dry feed should be fed dampened.
Affected horses should be kept away from hay and straw stores, and other horses stabled on these types of beddings. A complicating factor is that horses suffering from Equine Asthma due to dust should be turned out as much as possible, whereas horses affected by pollen may in fact worsen due to turnout in certain fields. These horses should be moved to low pollen areas until the pollen count has dropped.
Severe or chronic cases often require medication. In an acute severe flare up this is usually in the form of an injection of steroids to reduce the inflammation, sometimes accompanied by a drug called Atropine which helps to relax smooth muscle. Sometimes bronchodilators such as Clenbuterol are prescribed, however they work by opening the airways allowing the horse to breathe more easily, but do not treat the inflammation which is causing the airways to narrow.
Often it is necessary to prescribe oral (powder) or inhaled steroids to manage the condition longer term, as unfortunately the condition can take a prolonged period to settle, and flare up regularly.
In summary effective management is the key to owning a horse with Equine Asthma. Maintaining a clean, dust-free environment with good ventilation, combined with sensible storage of feed, bedding and any other dusty products will help reduce the severity of this condition.
In cases where good management is not sufficient, there are a selection of drug treatment options available. However it is important to stress that drug treatment alone without implementing good management changes will not facilitate control of this condition, it is a combined effort.