Julia Shrubb, MA VetMB CertAVP(EM) MRCVS, Ashbrook Equine Hospital.
Equine asthma (also known as heaves or dust allergy and formerly known as COPD or RAO) is one of the most common causes of coughing and nasal discharge in stabled horses.
Equine asthma occurs when the horse’s lungs over-react to inhaling allergens in the environment. It has many similarities to human asthma and symptoms can range from an occasional cough or under performance to severe wheezing and respiratory distress. It can affect any age of horse, but often starts in middle aged horses.
In severe cases, equine asthma can be diagnosed by simply examining the horse. More commonly an endoscopy and tracheal wash is performed to diagnose the condition. This is a minimally invasive and low risk procedure that is done under a small amount of sedation to pass an endoscope up the nose and into the trachea (windpipe). The trachea is visually assessed and a small amount of fluid is sampled to be analysed in the laboratory.
There are medications that are commonly used to treat the inflammation in the lungs and help relieve the symptoms of wheezing, coughing or nasal discharge. These include oral powders to help open up the constricted airways and/or reduce the hypersensitivity reaction as well as human asthma inhalers or nebulisers. However, a key consideration to the long term lung health is to reduce the animal’s exposure to the inhaled particles that cause lung inflammation. These include; mould spores, bacterial toxins, dust particles and ammonia, all of which are in higher concentrations in enclosed spaces with bedding and forage. Very occasionally, inflammation will be stimulated by external allergens such as pollens and if this is the case, management will need to be redressed in a different way as turnout may worsen the condition.
The best management for a horse with equine asthma stimulated by particles found indoors is 24 hour turnout, with no forage or bedding (even in field shelters). However, this is often not practical or possible. Instead there are management changes that can reduce the exposure to the inhaled allergens.
Forage and feeding:
Even well-made hay has large amounts of mould spores and bacterial toxins. Commercially sealed haylage has a much lower amount of allergen particles but may not be suitable for good-doers. Completely submerging hay in water for upto 30 minutes also reduces the amount of particles that are inhaled. Steaming hay in a proper commercially available steamer also has this effect. Home-made steamers are usually ineffective.
Feeding from the floor also reduces the amount of particles in the airspace as well as encouraging the natural drainage of mucous from the lungs.
The best types of bedding to use are rubber matting, dust extracted wood shavings or paper. Straw is not recommended. It is also worth considering bedding in the neighbouring stables especially if the airspace is shared such as in an American-style barn. Do not muck out or sweep with your horse in the stable as this dramatically increases the amount of allergen particles floating in the air.
All stables in the same air space need to be considered. Good ventilation is essential and simple measures like opening windows/roof space and not shutting barn doors can help. Lots of dust and cobwebs suggest poor ventilation. Moving a horse with equine asthma to a stable with better ventilation often makes a significant difference. The location of stored hay/straw and the muck heap should also be considered.
If you are concerned you horse may have equine asthma, please contact your vet for further advice.