Severe equine asthma shed light on by a new diagnostic test

Severe equine asthma is a common respiratory condition that impairs horse welfare. However, its pathogenesis remains poorly understood. Researchers have developed a new tool that enables more accurate diagnosis of the condition and identification of the causative allergens, allowing for therapies better tailored to each horse. This represents significant progress in combating a condition with a major economic impact.   Chronic inflammation of the deep respiratory tract in horses—now collectively referred to as equine asthma—is the second leading cause of poor performance, after musculoskeletal disorders, in sport and racehorses. Even without focusing on their significant economic cost to the equine industry, these conditions can considerably impair horse welfare, particularly in the case of older horses. It is therefore important to recognize them quickly in order to adapt the horse’s environment. Under this umbrella term, severe equine asthma (SEA) is a debilitating condition closely resembling human asthma. Found in 14% of horses in the Northern Hemisphere, it is the most common disease among horses kept indoors. Despite its prevalence, much remains unknown about this disease, particularly regarding its pathogenesis, with numerous conflicting reports. To date, the diagnosis of SEA remains limited, based primarily on the clinical history and easily identifiable clinical signs, supplemented by auxiliary diagnostic tests. While several studies have examined the potential benefits of in vitro allergen testing for the diagnosis of ASE, commercial application has been hampered by the limited range of allergens tested to date and a lack of statistical approaches leading to a clear classification of the disease. However, several studies agree on the role of immunoglobulin E (IgE) in the pathogenesis of ASE and its usefulness in detecting allergens. Building on these findings, researchers have therefore developed DNA microarrays to enable IgE profiling in horses affected by ASE in order to identify the causative allergens. A comprehensive DNA microarray platform was thus developed to enable the simultaneous detection of allergen-specific equine IgE in serum against a wide range of putative allergenic proteins. The chips identified a plethora of new proteins from pollen, bacteria, molds, and arthropods that are significant in the etiology of SEA—proteins that had already been implicated in allergic asthma reactions in humans. Among these are molecules derived from latex, which is traditionally ubiquitous in the horse’s environment, particularly on the surface of racetracks. Exposure to latex could therefore be detrimental to the horse’s respiratory health. Further research is needed to determine the levels of latex exposure in the equine environment and its in vivo effects. This work proposes an innovative and rapid approach for diagnosing ASE and, above all, for identifying allergens. The health, well-being, and performance of horses affected by SEA will be greatly improved by this microarray platform, which offers a new and effective serological diagnostic solution while also enabling a better understanding of the disease’s pathogenesis and the identification of new allergens. This would lead to tailored disease management based on sensitization profiles and the development of allergen-specific immunotherapies.