A new test is being developed to diagnose equine asthma in horses.  The term equine asthma has only been used for a few years but the disease has been around for many years.  In the past it was called heaves, chronic obstructive pulmonary disease or COPD, and recurrent airway obstruction or RAO.  I am not sure why the names of diseases keep changing, but supposedly it is to better describe the condition.  Regardless, if you have heard of heaves or COPD in horses, then asthma is the same condition.  Dr. Stacey Oke indicates in The Horse magazine that symptoms of asthma in horses can be mild or severe, like asthma in people, and severe symptoms in horses involve an increased respiratory rate and rhythm at rest plus a cough.  Horses with mild asthma might just have decreased performance, while those with moderate disease may cough and have other respiratory signs that could be misdiagnosed as an infection.  To accurately diagnose the condition, a bronchoalveolar lavage is required in which your veterinarian will place a small tube in the sedated horse’s lung, introduce some sterile saline, and then remove the fluid for analysis. 

However, Dr. Jean-Pierre Lavoie From Canada says there may be an easier method by using biomarkers circulating in the blood to identify asthma.  The researchers have identified three different biomarkers and found that the presence of these biomarkers effectively can determine all horses without the disease, but only can determine 57% of those that actually have it.  Still, ruling out 100% of the horses that do not have the disease is important in the diagnosis as the veterinarian at least knows the problem is not asthma.  Treating for asthma can cause increased disease if the horse has an infection, not asthma.