Equine Asthma

March 28, 2022

Have you noticed your horse is coughing, perhaps whilst eating or starting to exercise?

At the end of the Winter, after increased periods of being stabled and eating dry forage, susceptible horses are more likely to be suffering from Equine Asthma, a term which describes conditions previously classed as Recurrent Airway Obstruction (RAO), Inflammatory Airway Disease (IAD) and Chronic Obstructive Pulmonary Disease (COPD). Like humans, some horses will experience more severe disease than others, but any symptoms should be thought of as significant.

What is Equine Asthma?
Equine asthma is an inflammatory disease of the smaller airways (bronchioles and alveoli) caused by an allergy
to inhaled dust particles, spores and pollens. Therefore although it is usually seen in stabled horses it may also be present seasonally in horses living out during the Summer. The reaction in the airways causes increased production of fluid /mucus and airway wall constriction and thickening, which can be progressive over time. This obstruction of the airways causes increased respiratory rate and effort as well as coughing to clear the mucus.

What should I look for?
Clinical signs you notice may be:
• Exercise intolerance
• Coughing (spontaneously at rest or during exercise)
• Increased respiratory rate (should be 8-12 breaths per minute at rest)
• Nasal discharge (white and mucoid)
• Flared nostrils
• Abdominal effort during expiration (breathing out)
• Acute respiratory distress with loud wheezing in severe cases

How is it diagnosed?
Equine asthma is often presumptively diagnosed by the clinical signs, the horse’s environment and response
to treatment. However, visualising the airways using endoscopy and taking bronchoalveolar lavage samples to
look for inflammatory cells and bacteria is the preferred and definitive method. This will assess the severity and
distinguish it from other causes of respiratory disease such as infection.

How is equine asthma treated?
The key to treating Equine Asthma is in the horse’s management. Milder cases of equine asthma can be controlled by simply altering the horse’s environment and diet, whereas more severe cases will need extra
intervention in the form of short or long term medication. Environmental management for dust or spore allergies, the horse’s exposure to these should be minimised as much as possible. A dust-free bedding such as wood shavings or cardboard should be used, and horses fed a good quality, dust and mould free forage. Haylage is the ideal forage for these horses, or hay can be soaked or steamed. Most importantly, the more time the horse can spend in the field eating grass the better! Well ventilated stabling is also important and good hygiene with all un-eaten forage removed daily. Horses with pollen allergies can be harder to treat as
pollen avoidance is more difficult. Turnout in different fields with a lower pollen count may help, or moving
yards is sometimes a necessary option. Medical management in acute asthma attacks, horses may be injected
with medicines to dilate their airways and reduce inflammation, such as atropine, clenbuterol and
corticosteroids. Short term oral medication to manage bronchoconstriction and inflammation may be given
such as clenbuterol or prednisolone, these will reduce the symptoms whilst the management changes are
Some horses need long term medical management of their symptoms, and this is preferably in the form
of inhaled bronchodilators and steroids. Most horses tolerate inhalers well and they are more cost-effective
and have fewer side effects than oral medications as they target the airways directly. It must be emphasised however that they should be used in conjunction with dust-free management and not as a substitute!

Equine asthma is an allergy to elements in a horse’s environment, causing difficulty breathing due to airway
obstruction. It can be diagnosed by endoscopy and the key to treatment is avoidance of the causal allergens,
which may be dust, spores or pollens. Symptoms can be reduced using bronchodilators and corticosteroids, these may be oral or inhaled and some horses may require long term treatment as it is a condition for life.

Click here to speak to one of our vets about equine asthma.