EQUINE VETERINARY EDUCATION Equine vet. Educ. (2022) 34 (7) 355-361 doi: 10.1111/eve.13418


Original Article


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


J. C. F. Beling†* , D. M. S. A. Santos†, M. P. Ferreira†, P. C. A. R. Silva†, M. F. M. Costa‡ and D. A. B. Lessa† †Faculdade de Veterin


aria, Departamento de Patologia e Clınica Veterin Fluminense, Niter


University of Pennsylvania, Philadelphia, Pennsylvania, USA *Corresponding author email: joana_beling@yahoo.com.br


Keywords: asthma; bronchoalveolar lavage; horse; inflammatory airway disease


Summary 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.


Introduction


According to the literature, inflammatory airway disease (IAD) and recurrent airway obstruction (RAO) are two of the most important respiratory diseases affecting horses (Mazan 2018), causing significant economic losses to the equine industry worldwide (Wysocka and Kluci


nski 2014).


Recently, a phenotypic classification was suggested to include IAD and RAO under the term equine asthma


History


syndrome (EAS). According to the newly introduced classification criteria, IAD was classified as mild-to-moderate EAS, while RAO was classified as severe EAS (Bullone and Lavoie 2017). Detailed description of the phenotypic characteristics of each classification, together with diagnostic criteria, is presented in a Consensus published in 2016 (Cou€


etil


et al. 2016). Despite careful description of cytologic findings from bronchoalveolar lavage fluid (BALF) samples, the Consensus is unclear as to the cut-off point to classify EAS into mild or moderate and emphasises that the conditions are not necessarily part of a continuum. Combining clinical, endoscopic and cytologic criteria, summarised in Table 1 (Cou€


etil et al. 2016), a better diagnosis of EAS can be


achieved. Equine asthma syndrome is well documented and


prevalent in horses participating in several equestrian sport modalities, such as horseracing, endurance and dressage (Burrell et al. 1996; Wood et al. 2005; Courouce-Malblanc


TABLE 1: Summarised phenotypic characteristics of equine asthma syndrome


Characteristic Airway


endoscopy


EAS—mild to moderate


Excessive mucus in the tracheobronchial tree*


BALF cytology Mild increase in neutrophils, eosinophils and/or metachromatic cells


Age of onset Younger horses to mature


Clinical features


Occasional cough, poor athletic performance, increased respiratory effort post-exercise, signs for at least 4 weeks


Stable environment EAS—severe


Excessive mucus in the tracheobronchial tree*


Moderate-to-severe neutrophilia


Older than 7 years of age


Frequent cough, exercise intolerance, increased respiratory effort at rest, large variation of clinical signs over time


Exposure to dust or allergens; stable or pasture


*Other infectious causes of increased mucus secretion should be eliminated. Excessive mucus classification according to Hinchcliff et al. (2014). Adapted from Cou€


etil (Cou€ etil et al. 2016). © 2021 EVJ Ltd aria (MCV), Universidade Federal oi, RJ, Brasil; and ‡Faculty of Veterinary Medicine, Department of Biomedical Sciences, The


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