Equine asthma

Equine asthma is now the collective term used to describe respiratory disorders otherwise known as COPD, IAD, RAO or heaves.  The terminology is related to its clinical, histological and functional features as well as its similarities to human asthma.

It is commonly recognised that winter is a risk period for exacerbating signs of equine asthma as the horses generally spend more time stabled during these months.  However, during the Spring-Summer months we often see a rise in respiratory cases despite turnout.  An increase in environmental temperature and humidity is directly correlated to an increase in pollen and spore content. This negatively affects the lung function of asthmatic horses, worsening their airway obstruction and in turn exacerbating clinical signs.

Signs to look out for:

• Nasal discharge
• Cough
• Increased respiratory rate and effort
• A ‘heave line’ (developed from the increased effort using chest and abdominal muscles)
• Exercise intolerance
• Nostril flare, extended neck position (sometimes observed in acute respiratory attacks)

Diagnosis?

This is largely based on presentation, history and clinical examination.

As a gold standard it is often necessary to carry out an endoscopic examination of your horse’s airway to retrieve a tracheal and bronchial sample. This allows direct visulisation of the airway, analysis of the samples to determine the extent of the inflammation and can rule out infection as a contributing factor.

Treatment

Environmental management is key in controlling trigger factors and can often be effective without having to instigate treatment:

• Improve ventilation – open windows at back of stable/air vents
• Muck out/feed when horses are turned out
• Stable away from muck heap
• Dust free bedding (be mindful of neighboring stables and shared airspace!)
• Haylage or steamed hay (if soaking hay only need to soaked for ~ 1 hour)

If management alone is not enough to cause any clinical signs to subside, medication may be needed. This may differ depending on chronicity of the disease and systemic and inhalational therapies are available options; the latter is more often utilised in long-term management and prevention.  The drugs work by opening up the airway (bronchodilators), reducing mucus (mucolytics) and reducing inflammation (anti-inflammatory steroids).

Systemic medication:

Bronchodilators

– Clenbuterol (‘Dilaterol’, ‘Ventipulmin’)

– Hyoscine butylbromide (‘Buscopan’)

– Atropine

Potential anti-inflammatories

– Corticosteroids (‘Dexamethasone’,‘Prednisolone’)

Mucolytic

– Dembrexine (‘Sputolosin’)

Inhalational medication*:

Bronchodilators

– Ipratropium bromide

– Salbuamol/Salmeterol

Potential anti-inflammatories

– Beclometasone dipropionate

– Fluticasone propionate

*Inhalational medication can be administered via an inhaler (metred dose inhaler used with a spacer device) or a nebuliser