Broken-Wind, Heaves, COPD, SPAOPD, IAD, RAO, SPARAO and Equine Asthma – Why do they keep changing the name? A short history of equine allergic lung disease.
When I started my research career at the Animal Health Trust I worked closely with Dr Colin Roberts, an equine vet and medicine specialist, who was undertaking a PhD on equine respiratory health. Colin features on a lot of my papers and vice versa. At the time the most common terms used by horse owners for allergic lung disease in horses was “broken-wind” or “heaves”, the latter more commonly used in North America. Of course “wind” is a variation on air or breathing and hence horses with the disease were considered effectively to have “broken lungs”. The term heaves was descriptive and a direct reference to the exaggerated breathing efforts horses with obstructed airways have to make in order to move air in and out of the lungs. When in crisis (when the symptoms are severe), affected horses can be heard to grunt and the chest can be seen to be heaved upwards as they try to force air into their lungs. If you have seen a horse in crisis its unpleasant and distressing and certainly not something you will want to see again.
If we go back almost 80 years vets at the time were referring to “broken-wind” and “heaves” by the terms chronic airway disease, chronic bronchiolitis, chronic bronchitis, alveolar emphysema and chronic alveolar emphysema. Many vets suspected that this was an allergic condition brought on by exposure to dusty straw bedding or hay. Around the same time, medics were discussing “Farmers Lung”, a condition brought on by working with dusty hay and straw. At the time there was no real discussion about the common environment that seemed to be causing similar conditions in farmers and in their horses.
The term “chronic obstructive pulmonary disease” (COPD) came into use gradually in human medicine in the 1960s and 1970s replacing the previous term “chronic bronchitis and emphysema”. Pioneers in equine respiratory medicine Bob Cook and the late Peter Rossdale discussed many of the similarities of human and equine “emphysema” as early 1963 in the Proceedings of the Royal Society of Medicine in an article entitled Respiratory Distress in Some Diseases of Man and Animals. In fact, they even began to discuss the similarity to a human asthma but it would be a long time until this began to be taken up and in fact the veterinary world adopted the term equine COPD to describe “broken-wind”. And another researcher, FC Lowell, in 1964, also identified similarities between “heaves” and asthma in a paper in the Journal of Allergy in 1964 entitled: Observations on heaves. an asthma-like syndrome in the horse. But these attempts to link human and equine asthma were ignored and the veterinary world adopted the term equine COPD.
Whilst most horses are triggered and worse as a result of exposure to hay and straw or other dusty/mouldy bedding and are better turned out than in the stable, there are a sub-population of horses which are worse when outside and better inside. These horses are sensitive to pollutants and pollens and dust outside. The term adopted for these horses was SPAOPD – Summer Pasture Associated Obstructive Pulmonary Disease.
Equine COPD was used as the term for “broken -wind” into the mid 1990’s but it was becoming increasingly clear that COPD in people was a condition caused mainly by smoking (~90% of cases), although people who have never smoked can develop COPD for example if they work in smoky or dusty environments. Air pollution, chemicals and fumes can also cause COPD. So it became clear that as horses don’t some the use of the term COPD was no longer appropriate. As a result of a number of workshops and conferences where the terminology was discussed, some of which I can recall attending, a suggestion was made to describe the condition based on one of its classic clinical signs; that of airway obstruction. To this was added recurrent to allude to the fact that horses with “broken -wind” have a chronic condition characterised by periods of “remission” when they appear to be relatively healthy (although in reality they still have permanent lung damage, ongoing inflammation and mucus over-production but it is just not apparent without invasive examination) and periods when they show clear evidence of disease through cough, nasal discharge and increased respiratory effort (e.g. heaving and nasal flaring). So the term RAO was adopted. This also meant that SPAOPD now became SPARAO – Summer Pasture Associated Recurrent Obstructive Pulmonary Disease.
And horse owners have also had to contend with a long period of confusion as vets and researchers around the world also argued over the condition which became known as IAD or Inflammatory Airway Disease. So if “broken-wind”/”heaves”/COPD/RAO are all inflammatory then what makes IAD different? IAD was primarily used initially to describe airway inflammation in young horses and was considered something that they could grow out of whereas “broken-wind” was something that typically occurred in horses over ~7 years of age and was a chronic/irreversible condition. To complicate things further IAD has also been referred to as “mild to moderate equine asthma”.
So, finally, after many years of debate and disagreement, it finally became clear that the condition we referred to variously by “Broken-Wind”, “Heaves”, equine COPD, SPAOPD, IAD, RAO, SPARAO did in fact share almost all the features of human asthma and so in around 2015 the term equine asthma was adopted. And hopefully this time it is set to stay as equine asthma for a long time!
