Equine Asthma

 Equine asthma, formally known as COPD (Chronic Obstruction Pulmonary Disease), RAO (Recurrent Airway Obstruction), SPaRAO (Summer Pasture associated RAO) or heaves. The new terminology of asthma is an umbrella term for all forms of equine allergic respiratory disease and relates to a hypersensitivity or an allergic reaction to inhaled allergens such as mould spores, pollens or dust mites. Equine asthma is commonly seen in winter when horses are stabled; however, some horses are allergic to pollens and grasses in the environment and so the disease is only seen summer when they are turned out.

Many horses will be allergic to multiple allergens and may be simultaneously allergic to pollen in the pasture and allergens in the stable. This makes management of these case challenging.

pastedGraphic.pngSigns of the disease

Those affected will frequently have one or more of the following:

  • Cough.
  • Nasal Discharge.
  • Increased breathing effort sometimes with the presence of a ‘heave’ line (see picture below).
  • Poor performance.

Diagnosis
Diagnosis may be made from chest auscultation or may require a more in depth investigation such as upper airway endoscopy. Samples can be taken from a horse’s airway to aid diagnosis.

A small number of horses will have a concurrent and very mild bacterial infection when suffering from asthma. This can only be diagnosed from sample collection.

 

Control of the disease
The most important factor to consider in controlling asthma is good air hygiene. Allergens from hay are the most frequent agent causing asthma but those from pollens and straw bedding are also important. Thus horses suffering from this disease should, in an ideal world, never be stabled and be turned out 24-hours a day with access to a 3-sided shelter. This is frequently not practical and the horse should be housed in a well-ventilated stable with minimal dust bedding (not straw) and should be fed haylage rather than hay as it contains fewer allergens. If hay must be fed it must be soaked for 20 minutes and fed whilst still wet. No further soaking is required otherwise nutrients will be leached. 20 minutes soaking will ensure that all allergens are removed. Haylage or hay should be fed off the ground and not in the usual hay nets.

Horses with summer pasture associated asthma should be housed in the summer months in order to prevent contact with the irritants, this can sometimes prove very difficult as the allergen may be airborne.

 Good management in either case will often reduce the majority of clinical signs.

 

Medical treatment
When the airways are irritated by the allergens they become narrower, thicken and produce more mucoid secretions. Drugs prescribed for your horse will reduce these affects. Bronchodilators such as Ventipulmin act to open the narrowed airways however long term use can reduce their effectiveness.

Steroids have an anti-inflammatory action, dampen down the allergic response and can prevent scarring of the airways. Steroids are not commonly used for long-term treatment due to small but significant side effects; however they may be used at the beginning of treatment. Injectable steroids may be replaced with the tablet form if longer-term therapy is required.

The latest available treatments for asthma are inhaled steroids; they are much safer as the steroid is retained mostly within the lung tissue. They are administered through a metered device inhaler (MDI) with a volumatic spacer or a Nebuliser.

pastedGraphic_2.pngpastedGraphic_1.pngSpecially designed equine nebulisers are the ‘gold standard’ method of administering drugs into your horses airway. They are easy to use and allow certainty that your horse is getting all of the drugs. Additionally different drugs can be used when necessary. They can also be used for ‘maintenance’ whereby some horse can benefit from daily saline nebulisation.

Dosage of any medication depends upon the size of the horse and the severity and chronicity of disease. This will all be explained when you are first introduced to the equipment. The general idea is to combat the disease in its acute stages and then reduce the medication to the lowest effective dose for long term management.

Mucolytics break down the increased respiratory mucous, however their efficacy is often limited and they commonly do not relieve clinical signs.

If you think your horse may be suffering from asthma then please contact the office and speak to one of the vets.