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Equine Asthma- Not just a winter issue!

Updated: Feb 22, 2023

Author: Lucy Carmichael BVSc MRCVS

Traditionally, we tend to assume that horse’s coughs and breathing issues are associated with dusty hay and straw, so we generally think of it affecting horses which stand in during the winter months. However, we need to think of equine asthma as a year-round issue, as in the warmer months, we recognise summer pasture associated obstructive pulmonary disease or ‘SPAOPD’.

As with the more ‘classic’ equine asthma, SPAOPD normally presents for the first time in horses aged between 8 and 12 years old, and of any sex and breed. However, it occurs in response to allergens such as pollens and outdoor moulds. When they are breathed in, the horse’s airways react, becoming inflamed and constricted. They also start to produce greater quantities of mucus, which cannot be efficiently cleared. These factors make it more challenging for the horse to breathe, causing the development of the outward symptoms that we see such as:

  • Increased respiratory rate and effort

  • Chronic cough

  • Clear or white nasal discharge

  • Wheezing

  • Excess mucus

  • Poor performance/exercise intolerance


Your vet will initially examine your horse, which will include careful auscultation (listening with a stethoscope) to the horse’s lungs.

The most accurate way of diagnosing equine asthma is to perform an endoscopy of the horse’s airways. This involves passing a camera up the horse’s nose to examine the nasal passages, larynx (throat), and trachea (windpipe). It also allows us to take samples, normally via a tracheal wash. Sometimes the tracheal wash is combined with a bronchoalveolar lavage. In these procedures, sterile saline is instilled into the airways, before being sucked back up in a syringe. This facilitates the safe withdrawal of cells, bacteria, mucus, and any other contaminants which could be causing the respiratory disease.

The samples are then examined under a microscope, to look for the possible causes of the symptoms, and allowing us to definitively diagnose equine asthma. In some cases, your vet may recommend further tests such as blood samples if they suspect that there could be an underlying health condition making the horse more susceptible.

Performing airway endoscopy on a yard


Treatment primarily involves reducing exposure to allergens (such as pollen and fungal spores) as much as possible. This can be achieved by avoiding exercise during the middle of the day when it is hot, and keeping the horse in a cool, dust free stable during the day, or when the pollen counts are especially high. The pollen counts can be easily found online at the met office:

Once the horse has been examined by a veterinarian, and appropriate diagnostics have been carried out, treatment can be instigated such as inhalers, or systemic treatments such as oral steroids or antibiotics. In some cases, nebulisers may be required for management. In most cases, the asthma is seasonal, and the condition improves or resolves during the autumn and wither months.

If you have any questions, or are concerned that your horse could be suffering from equine asthma, please do not hesitate to contact the team at Donnington Grove on 01635 39039


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