EQUINE VETERINARY EDUCATION / AE / july 2022


359


10 µm


Fig 2: BALF cytology. Aqueous Romanowsky–Giemsa stain. Normal cytological features. Note the predominance of mononucleated cells (macrophages - red arrow and lymphocytes - yellow arrow) and rare neutrophil; bar 10 lm.


10 µm


Fig 4: BALF cytology. Aqueous Romanowsky–Giemsa stain. Cytopathological features compatible with mild asthma syndrome. Presence of eosinophil (white arrow) infiltrate in a moderate mucous background; bar 10 lm.


expectations. Eosinophilia is commonly seen in young racehorses as a response to inhaled particles (Ivester et al. 2014), and 78% of the horses in the present study were younger than 7 years of age. In temperate climates in the Northern Hemisphere,


between 10 and 20% of adult horses have been reported to present severe EAS (Hotchkiss et al. 2007; Leclere et al. 2011). In this study, only one horse (3%) had cytology compatible with moderate EAS as evidenced by eosinophilia above 5%. An effect of climate can be inferred (Davis and Sheats 2019), but we did not investigate the effects of temperature, humidity or seasonality on EAS given that a single collection was done. Breed did not play a role in each of the different criteria


10 µm


Fig 3: BALF cytology. Aqueous Romanowsky–Giemsa stain. Cytopathological features compatible with mild asthma syndrome. Note moderate numbers of neutrophils (red arrow) and activated macrophages (black arrow); bar 10 lm.


this sense, in the course of planning this study the authors decided to use neutrophil count in the BALF as a classification criterion for EAS severity. This choice was based


on clinical experience and the fact that neutrophils are the first cells recruited to the site of airway inflammation, despite the importance of eosinophils in the pathophysiology of asthma (Monteseirın 2009). Neutrophils have been recognised as drivers of asthma-associated airway remodelling and are the primary cells in noneosinophilic asthma phenotypes (Ciepiela et al. 2015). In horses, neutrophils rather than eosinophils are recruited to the lungs (Fairbairn et al. 1993), and equine heaves (RAO) has been demonstrated to be neutrophilic in nature (Lavoie et al. 2001). Total cell count in the BALF was greater than that


previously reported (Gerber et al. 2003) and there were more horses with eosinophilia than neutrophilia, in contrast to previous publications (Cullimore et al. 2018) and to our own


used for diagnosis of EAS, nor in the total number of positive animals; however, CAMPO had higher lymphocyte, while MM had higher macrophage percentages. The exact reason for this finding is unknown, and further studies are required to clarify this aspect. It can be hypothesised that differences might arise from vaccination protocols, stress or environment, rather than purely due to breed, although the present study did not investigate any of these factors. To investigate age as a factor in the diagnosis of EAS, we


compared horses with ages up to and including 7 years with horses older than 7. This division was based on the phenotypic description of mild and severe EAS presented in the Consensus (Cou€


etil et al. 2016). Our results indicate that


when mucus score and cytological findings are used as diagnostic criteria, age is not a factor in the occurrence of subclinical EAS. A similar finding was published previously (Gerber et al. 2003). This study did not find any association between sex and occurrence of subclinical EAS, as previously reported for other horse breeds (Davis and Sheats 2019). Equine asthma constitutes a common cause of poor performance in horses (Pirie 2014; Cou€


etil et al. 2016). In this


study, HR and RR were measured as indicators of physiologic responses to exercise. Even though there were differences in baseline values in relation to reference ranges (Knottenbelt 2009), which could be attributed to heat or stress, immediately post-exercise and 30 min post-exercise values


© 2021 EVJ Ltd


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88