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.