EQUINE VETERINARY EDUCATION / AE / july 2022
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TABLE 2: Summary statistics of variables from Mangalarga and Campolina horses Age 7.1a
Vol
MM Mean MM S.D.
Campo Mean Campo S.D.
3.4
5.5a 1.6
175.5a 20.3
167.9a 13.8
TCC
848.0a 484.7
729.2a 563.3
%Ly
39.9a 15.5
53.6b 5.8
%Mc 54.5a
17.3
40.3b 5.1
%Ne 2.7a
1.8
3.7a 1.6
%Eo 1.4a
1.2
1.2a 1.2
%Ms 0.4a
0.3
0.4a 0.5
%Epi 0.9a
0.7
0.8a 0.7
Age, Vol = recovered volume of saline (mL); %Eo, % eosinophils; %Epi, % epithelial cells; %Ly, % lymphocytes; %Mc, % macrophages; %Ms, % mast cells; %Ne, % neutrophils; Campo, Campolina breed; M, Mangalarga Marchador breed; TCC, total cell count in BALF (cells/µl). Different superscripts in each column indicate a significant difference (P<0.05).
TABLE 3: Heart rates and respiratory rates (mean s.d.) from healthy and equine asthma syndrome-positive horses from two breeds before, immediately after exercise and 30 min post-exercise
MM H
Before Immediately post-exercise 30 min post-exercise
HR1 RR1 T1
HR2 RR2 T2
HR3 RR3 T3
37.3 5.6 24.0 9.3 37.5 0.3 79.8 6.9 57.5 24.8 39.3 0.4 40.5 5.7 33.3 18.0 38.3 0.2
MM EAS
42.4 8.1 35.3 7.0 37.5 0.4 67.8 12.3 79.8 26.4 38.9 0.6 41.1 4.6 35.9 14.7 38.0 0.2
CAMPO H
54.3 9.0 31.1 4.8 38.1 0.1 96.0 9.1 69.1 12.2 40.0 0.3 60.9 8.4 30.9 13.2 38.3 0.5
CAMPO EAS
46.0 7.0 19.3 7.8 37.3 0.4 83.8 10.8 63.0 16.0 39.5 0.4 58.3 7.8 33.3 13.3 38.3 0.2
CAMPO, Campolina breed; EAS, equine asthma syndrome group; H, healthy group; HR1, heart rate before exercise; HR2, heart rate immediately after exercise; HR3, heart rate 30 min post-exercise; MM, Mangalarga Marchador breed; RR1, respiratory rate before exercise; RR2, respiratory rate immediately after exercise; RR3, respiratory rate 30 min post-exercise; T1, rectal temperature before exercise; T2, rectal temperature immediately after exercise; T3, rectal temperature 30 min post-exercise.
test for independent samples showed no significant differences by breed in neutrophil (P = 0.12), eosinophil (P = 0.71), mast cells (P = 0.90), epithelial cell (P = 0.70) percentages and TCC in BALF, but a significant difference in macrophage (P = 0.02) and lymphocyte (P = 0.02) percentages. HR, RR and T means and standard deviations (SD)
separated by group (MM healthy and EAS, CAMPO healthy and EAS groups) are shown in Table 3. Apart from changes in HR, RR and T related to activity, all other physiological parameters and baseline haematology were within normal reference rages for the species. ANOVA demonstrated a significant variation in HR, RR and T attributed to individual horse (P = 0.003) and time (pre-exercise, immediately post- exercise or 30 min after exercise, P<0.001) in Mangalarga horses, while in Campolina horses the only significant variation was attributed to time (P<0.001). There was no significance in HR, RR and T attributed to state (healthy vs. EAS-positive, P = 0.47) in either breed. Only horses negative to all criteria as per the Equine Asthma Syndrome Consensus (Cou€
etil et al. 2016) were
considered healthy (n = 13). According to the various endoscopic/BALF diagnostic criteria listed in the material and methods section, 17 from the 30 horses (56.7%) in the sample were diagnosed as EAS-positive, although only one (3%) of these was classified as moderate due to eosinophilia above 5%. Fisher’s exact test showed no differences in the numbers of healthy and EAS-positive horses by breed (P = 1.0), age group (P = 0.40) or sex (P = 1.0). Individual observations for each of the diagnostic criteria are available in
Supplementary Item 1. The Mann–Whitney test showed no differences in mucus grades between breeds (P = 0.12). None of the horses presented with clinical signs of EAS during the experiment. When individual diagnostic criteria where considered, all
horses (17/17; 100%) diagnosed as EAS-positive through more than one criterium had TCC above 530 cells/µl, 52.9% (9/17) had elevated eosinophils and mucus scores, and 35.3% (6/17) had elevated neutrophils. Chi-square test showed no differences in percentages of positive animals as far as mucus score (P = 0.22), total cell count (P = 0.86), neutrophilia (P = 0.41) or eosinophilia (P = 0.50) between breeds. However, outcome percentages were significantly different for the various diagnostic criteria (P = 0.02, Fig 1), with per cent differences between observed and expected counts being larger than expected for TCC and lower than expected for neutrophils. Representative images of the BALF cytology are shown in Figures 2–4.
Discussion
This study demonstrated a high occurrence of EAS in asymptomatic horses, contributing to the notion that subclinical disease is prevalent among equine athletes. A recent publication has identified pathological changes in the airways of racehorses actively engaged in competition, even though histology rather than BALF cytology was used (Ter Woort et al. 2018). Other authors using endoscopic examination also found a high occurrence of EAS in seemingly healthy horses (Gerber et al. 2003; Cullimore et al. 2018; DavisandSheats 2019).
© 2021 EVJ Ltd
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