EQUINE ASTHMA – A new name for inflammatory airway disease

Non-infectious respiratory disease is a significant cause of poor performance in horses and knowledge in this field is expanding all the time. Recent research has led to the proposal that ‘equine asthma’ is more appropriate than previously used terms like inflammatory airway disease, recurrent airway obstruction and chronic obstructive pulmonary disease, based on the similarities with the human condition.

Dust, mould, fungi and noxious gases in the environment are thought to trigger inflammation and obstruction of the small airways. The condition is divided into three main categories based on severity. Mild cases may only show signs of poor performance with moderate cases showing an elevated breathing rate at rest and sometimes a cough.  Horses, unlike humans and other animals have a relatively weak cough reflex, so this sign is not very consistent. Horses with severe equine asthma have recurrent episodes of laboured breathing which may be quite dramatic and can require emergency treatment.

 

How is it diagnosed?

Lung function tests, which are often used to diagnose human asthma, are not feasible in general equine practice. So, in addition to the history and depending on the findings of a full clinical examination, tests may be recommended such as:

  • bloodwork to check for evidence of infection
  • endoscopic examination of the trachea (windpipe) to look for mucus
  • bronchoalveolar lavage (lung wash) – a small volume of sterile fluid is introduced into the lower airways and then suctioned out to obtain a sample of the cells for microscopic examination.

 

There is interesting research into new diagnostic techniques including the development of a miniature ultrasound probe which can be passed down the endoscope to assess the thickness and change in structure of the walls of the bronchi (mid-sized airways, deep within the chest). This may be helpful in the future to diagnose mild cases and allow prompt treatment to improve performance.

 

What about treatment?

Providing a well ventilated environment with as little exposure to dust and mould spores is key to managing equine asthma. Switching from straw to shavings or even rubber matting and feeding carefully soaked or steamed hay are all ways to reduce allergen exposure. In fact changing from straw to shavings and from hay to a complete pelleted diet achieves a 3 fold reduction in dust burden. Other changes such as reducing stabling times and moving the horse out of the stable whilst mucking out reduce exposure as well. Additionally, some horses may require treatment with either oral corticosteroids or clenbuterol to help open the airways or may require medication via a nebulizer or inhalers in the same way human sufferers are treated.

 

If you are concerned about your horse’s performance or think that your horse may be showing signs of equine asthma, ask your vet for more information.

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