Reasons for performing study: The diagnosis of equine recurrent airway obstruction (RAO) and inflammatory airway disease (IAD) is based on clinical signs and increased inflammatory cell percentages in the bronchoalveolar lavage (BAL) fluid. Since a BAL is an invasive procedure, a risk-screening questionnaire (RSQ) would be a valuable screening tool for lung inflammation.
Objective: To evaluate the accuracy of a RSQ to detect lower airway inflammation (LAI) in a large population of horses.
Methods: A standardized BAL was performed in the field on 167 horses in Alberta, Canada. Horses were separated into 3 categories: 1) BAL normal; 2) BAL mild to moderate LAI (MLAI), and 3) BAL severe LAI (SLAI). The horse owners were asked to complete a RSQ. The RSQ scores were compared to the BAL results to determine the likelihood of a horse having MLAI, SLAI or no LAI.
Results: Based on BAL cytology, 28 (17%) horses were normal and 139 (83%) were abnormal, with 110 (66%) showing MLAI and 29 (17%) SLAI. Horses with SLAI and MLAI had a mean RSQ score of 0.95 and 0.70, respectively, compared to 0.60 for normal BAL horses. Horses with SLAI showed more clinical signs than normal and MLAI horses. The sensitivity and negative predictive values of the RSQ for detecting SLAI using a cut-off score of 0.87, were excellent at 0.90 (95% CI 0.73-0.98) and 0.96 (95% CI 0.82-1.00). Questioned on the clinical signs typically found in RAO cases differed significantly between horses with BAL SLAI and those with BAL normal.
Conclusions: Prevalence of MLAI was high in this population. Although the RSQ did not allow differentiating normal horses from horses with MLAI, it has a high sensitivity to detect horses with SLAI and is therefore a good screening tool for SLAI.
Below is a short video on Andrea Wasko's Master's of Science project on heaves and inflammatory airway disease in Alberta Horses and bronchoalveolar lavages in horses.
Airway hyperresponsiveness, expressed as an increased in lung resistance (RL) by more than 75% at low bronchoprovocative concentrations of nebulized histamine (PC RL75), is a feature of inflammatory airway disease (IAD) in horses. Glucocorticoids are often used empirically to treat IAD however their effects on IAD have never been reported.
Objective: To determine if dexamethasone (DEX) (0.05 mg/kg IM SID) and inhaled fluticasone (FLUT) (3000 μg BID) administered by AeroHippus® are effective in decreasing airway hyperresponsiveness, the number of inflammatory cells in bronchoalveolar lavage fluid (BALF) and clinical signs in horses with IAD.
Methods: 8 horses with IAD were randomly assigned to a treatment group with either DEX or FLUT in a cross-over design study. All horses fulfilled the definition of IAD according to the ACVIM consensus publication. Lung mechanics during brochoprovocative challenges, BALF cytology, and scoring of clinical signs at exercise were the measured outcomes.
Results: One and two weeks of dexamethasone treatment abolished the increase in RL by 75% at any histamine bronchoprovocative dose in all horses. The FLUT treatment reversed the airway hypersensitivity after one week of treatment in all horses and after two weeks of treatment in 6 horses. Both DEX and FLUT also significantly decreased airway hyperreactivity after one and two weeks of treatment. There was a significant decrease in the number of lymphocytes after treatment with both DEX and FLUT but no significant differences in other BALF cell types or total cell counts. There was no difference in the scoring of the clinical signs during each treatment and wash-out period.
Conclusion: Both DEX and FLUT treatments significantly inhibit airway hypersensitivity and hyperreactivity in horses with IAD. There was no significant effects on the clinical signs or the number of most inflammatory cells in BALF. The treatments have no residual effect 3 weeks after discontinuation.
Objectives: The pathophysiology of inflammatory airway disease (IAD) is unknown, but in some cases involves the accumulation of mast cells, neutrophils or both in the BALF. The objective of this study was to characterize cytokine gene expression in the BALF cells of horses with IAD, including a comparison of cytokine gene expression between IAD horses with increased BALF mast cells (IAD-Mast) or neutrophils (IAD-Neutro).
Methods: The mRNA expression of IL-4, IFN-g, IL-17, IL-8, IL-1b, IL-5, IL-6, IL-10, IL-12p35 and eotaxin-2 was studied by quantitative polymerase chain reaction (QPCR) with effiency correction in BALF samples of 17 horses with IAD (IAD-total), also subcategorized as 8 IAD-Mast and 9 IAD-Neutro, and 10 controls. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) was used as a reference gene. Relative expression software tools (REST) analysis provided ratios of expression, statistical analysis, and confidence intervals for the results.
Results: Compared with the control group, IL-5, IL-1b, IL-6, IL-8, and IL-10 mRNA expression was up-regulated 3.5-, 3.4-, 2.8-, and 1.9-fold respectively, in the IAD-total group. The IAD-Neutro group showed increased expression of Il-17, IL-8, and IL-5 (4.7-, 2.5-, and 2.9-fold respectively) and a decreased expression of IL-4 (3.4-fold) compared with the IAD-Mast group.
Conclusion: Cytokines from the Th2 family plays a key role in IAD and a difference pathophysiology may be involved in mast cell versus neutrophil BALF accumulation in IAD horses.
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