Post-exercise endoscopic and cytologic diagnosis of equine asthma syndrome in asymptomatic Brazilian pacers

The objectives were: 1. to investigate the occurrence of equine asthma syndrome (EAS) in a group of Campolina and Mangalarga Marchador horses through post-exercise respiratory endoscopy and cytology; 2. compare the efficiency of different diagnostic criteria; and 3. compare the incidence of EAS by breed, age group and sex. A standardised exercise test was conducted in the field, followed by respiratory endoscopy and bronchoalveolar lavage and fluid collection 30 min post-exercise. Clinical evaluation pre- and post-exercise, respiratory endoscopy post-exercise and bronchoalveolar lavage, also post-exercise, were conducted in 30 horses (15 Campolina and 15 Mangalarga Marchador) aged 3–18 years, without a history of respiratory illness and without clinical evidence of active respiratory disease. All horses were in active training and were considered fit to participate in equestrian competition characteristic of these breeds. Post-collection, the horses were subdivided into healthy or EAS-positive, depending on several diagnostic criteria. Statistical comparisons between breeds, age brackets (up to 7 years of age and above 7 years of age) and sex were conducted using appropriate statistical tests. According to bronchoalveolar lavage fluid (BALF) cytology, 56.7% of the horses showed at least one inclusion criteria that contributed to classification as EAS-positive. Of those, only one was classified as moderate EAS, while the others were classified as mild. Total cell count in the BALF above 530 cells/µL was the single most common diagnostic criteria (100%), followed by increased tracheal mucus (53%) at endoscopy, eosinophilia (47%) and neutrophilia (35%) in BALF. Significant differences were found between macrophage and lymphocyte numbers according to breed, but no other differences between breeds, age brackets, sex or status (healthy vs. EAS-positive). A high occurrence of EAS was found in competition-ready Mangalarga and Campolina pacer horses in this study.