Study population
Among the 174 horses sampled, 3 horses were excluded because samples were uninterpretable on reception at the laboratory, and 16 were excluded from the study because of respiratory issues unrelated to equine asthma: 10 with infectious pneumonia, 5 with exercise-induced pulmonary haemorrhage (EIPH) and 1 with interstitial pneumonia. Overall, 155 horses were included. The population was composed of 85 Standardbred racehorses (54.8%), 20 sport horses (12.9%), and 50 leisure horses (32.3%). Horses were aged from 2 to 25 years (median 6 years), with a total of 38 entire males (24%), 60 geldings (39%) and 57 females (37%).
Of these, 85 horses were diagnosed with MA, 35 horses were SA and 35 horses were considered controls (CTL). Amongst the MA group, 29.4% (25/85) exhibited mast cell inflammation only, 2.4% (2/85) eosinophilic inflammation only, 43.5% (37/85) neutrophilic inflammation only, 11.8% (10/85) increased tracheal mucus score only and 12.9% (11/85) had a mixed pattern amongst the four inclusion criteria. All horses had a TBS of 0.