Equine Pasture Asthma in Brazil
Authors: Gouvêa Liana Villela de , Bernardes Camila , Helayel Michel José Sales Abdalla , Alencar Nayro Xavier de , Costa Maria Fernanda Mello , Lessa Daniel Augusto Barroso 
Published: June 2021

Background: Summer Pasture Associated Obstructive Pulmonary Disease (SPAOPD), or Equine Pasture Asthma (EPA), as termed by Ferrari et al. [17], has been described as an environmentally-induced respiratory disease that occurs during the warmer and more humid months, leading to reversible airway obstruction, persistent and non-specific airway hyper-responsiveness, and chronic neutrophilic airway inflammation. Exacerbation of clinical signs vary according to warm seasons, and range from mild to severe episodes of wheezing, coughing, and laboured breathing in a chronic state that is debilitating for the equine [4]. This report describes two cases of Equine Pasture Asthma that show clinical and environmental similarities with Summer Pasture Associated Obstructive Pulmonary Disease.Case: The patients were crossbreed geldings that have never been stabled and were used for cattle management in a farm in southeastern Brazil. They presented poor performance and a persistent cough for over 3 years. Initially, the respiratory signs were only observed after exercise but, over the years, it gradually progressed to being observed when the horses were at rest. Both animals had a history of regular deworming and were previously treated by other veterinarians with antibiotics, clenbuterol, and mucokinetics. Little improvement was noticed by the owner and the signs returned over time as treatment was often discontinued. Clinical findings were compatible with the grade 3 mucus classification of Gerber et al. [18] as well as with score 2 for Severe Asthma of Davis and Sheats [13]. BALF cytology was done following the technique described by Couetil et al. [10]. Animal 1 presented slides with free yeast; macrophages and mucus with Curschmann’s spiral and counting of 29,7% of neutrophils (NE), 43,7% of lymphocytes (LP), 25,3% of macrophages (MC) and 1,3% of eosinophils (EO). Animal 2 presented slides with phagocytized yeast, mucus and counting of 27% of NE, 38,5% of LP, 33% of MC and 1,5% of EO.Discussion: Diagnostic findings fit the clinical score 2 (from 0 to 3) for Severe Asthma [13], where the animal presented frequent cough with periods of no coughing, nostrils flares in inspiration and exhalation, obvious abdominal flattening and “heave line”, pulmonary auscultation with crackles, and scarce mucous nasal discharge. The cytological findings of our reported cases also falls within the Severe Asthma classification [13], when the specific counting of 300 cells is equivalent to ≥20% of neutrophils on BALF analysis and the animal present increase in respiratory rate/effort at rest. Similar counts were found by Costa et al. [9] counting 200 cells, Rossi et al. [28] also counting 300 cells, and Couetil and Thompson [11] counting 5 fields (of at least 100 cells) on a cytocentrifuge smear. The present report took place in a region of the Rio de Janeiro State, southeastern Brazil, which shows predisposing climatic characteristics similar to those described in previous SPAOPD reports. Yet, this very climate remains somewhat constant throughout the year, as seasonality in the Rio de Janeiro State is not as marked as in the Northern Hemisphere. Given this contrasting aspect, we believe that the term Equine Pasture Asthma, instead of SPAOPD, is more appropriate to describe the cases presented here. Also, to the best of the authors’ knowledge, this is the first documented description in Brazil of Equine Pasture Asthma in animals that were never stabled or fed with hay. This documented evidence of a chronic respiratory condition consistent with Equine Pasture Asthma but little related to seasonal changes presents as a warning to other possible cases that might be unnoticed in equine herds in Brazil and in similar climates.