Co-Occurrence of Severe Equine Asthma and Palatal Disorders in Privately Owned Pleasure Horses

SIMPLE SUMMARY: Asthma is one of the leading problems affecting the lower airways in equids. At the same time, palatal disorders, including primary palatal instability and dorsal displacement of the soft palate, are common problems affecting the equine upper airways. In human medicine, “one airway, one disease” is a widely accepted concept describing the anatomical, physiological, and immunological connections between upper and lower airways. Clinical studies have already highlighted co-occurrences and associations between lower airway diseases, such as asthma, and upper airway diseases, such as rhinitis, rhinosinusitis, vocal cord dysfunction, or obstructing sleep apnea in people. However, only a few studies have explored co-occurrences and associations between asthma and palatal disorder in horses. This study aimed to investigate the occurrence of palatal disorders in horses affected by severe asthma in exacerbation and to assess whether a decrease can be observed after treatment-induced disease remission. The presence of palatal disorders was investigated by overground endoscopy in forty-six horses diagnosed with severe equine asthma before and after asthma treatment. Palatal disorders were diagnosed less frequently in remission after asthma treatment than during exacerbation before treatment, suggesting that both asthma and palatal disorders may respond to similar treatment plans. ABSTRACT: According to the “unified or united airway disease” theory, diseases in the upper and lower airways frequently co-occur because they represent a single morphological and functional unit. Palatal disorders (PDs) and severe equine asthma (SEA) are frequent diseases that, respectively, affect upper and lower equine airways; however, clinical studies focusing on the co-occurrence of PDs and SEA are limited. The present study investigated the prevalence of PDs in horses affected by SEA, and whether prevalence decreased after SEA treatment. Forty-six privately owned horses affected by SEA in exacerbation were included. For each horse, the severity of the asthma clinical signs was assessed using a previously described scoring system, and the co-occurrence of palatal disorders was investigated using overground endoscopy, before and after treatment for SEA. Before treatment (in exacerbation), 67.4% of SEA-affected horses showed evidence of PDs, including 39.1% showing evidence of palatal instability (PI) and 28.3% of dorsal displacement of the soft palate (DDSP). Airway inflammation (neutrophil percentage in the tracheal wash and bronchoalveolar lavage fluid) was worse in horses with co-occurring PDs. After treatment (in remission), no horses showed evidence of PI, while DDSP was diagnosed in 8.7% of horses. These findings suggest that palatal disorders respond to asthma treatment, supporting the hypothesis that both diseases could be manifestation of a common underlying disorder.