Fungi in respiratory samples of horses with inflammatory airway disease

BACKGROUND: Fungi contribute to the inflammatory response of lungs in horses with recurrent airway obstruction and in some forms of asthma in humans. The role of fungi in inflammatory airway disease (IAD) has not been assessed. OBJECTIVES: Evaluate the prevalence of fungi in the respiratory samples of horses diagnosed with IAD, describe clinical signs associated with the presence of fungi in respiratory samples, and assess the risk factors associated with IAD and with the presence of fungi in the airways. ANIMALS: Seven‐hundred thirty‐one active horses referred to a specialized ambulatory practice for signs of respiratory disease or poor performance. METHODS: A prospective observational study was performed, collecting clinical data, environmental conditions, and results of a tracheal wash (TW; cytology, fungal culture, and bacterial culture), and bronchoalveolar lavage (cytology). RESULTS: A positive fungal culture was obtained in 55% (402/731) of horses. Horses with fungal elements observed on the TW cytology had 2 times greater chance of having IAD than horses without fungi (odds ratio [OR] = 2.1; 95% CI 1.08‐3.33; P = .0003). Risks of being diagnosed with IAD and likelihood of fungi in TW were higher when horses were bedded on straw (OR = 2.0; 95% CI 1.2‐3.2 and OR = 1.9; 95% CI 1.3‐2.6, respectively) or fed dry hay (OR = 2.7; 95% CI 1.7‐4.4 and OR = 2.6; 95% CI 1.6‐3.4, respectively). CONCLUSIONS AND CLINICAL IMPORTANCE: Horses inhaling aerosolized fungal particles are at a significantly higher risk of developing IAD. The type of bedding and forage represent significant risk factors for IAD and fungal contamination of equine airways.