Influence of climatic changes on respiratory health in a teaching herd of outdoor-housed horses.
Authors: Calomeno Stefano Strano, Freitas Santi Thasla de, Barbosa Bianca, Weber Saulo Henrique, Oliveira Tiago Marcelo, Machado Gisele Fabrino, Michelotto Pedro Vicente
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary A teaching herd of 17 outdoor-housed horses in southern Brazil underwent repeated airway sampling across winter, spring and summer to investigate whether seasonal climatic variations influence respiratory health in horses maintained in a lower-allergenic environment than typical stabled animals. Researchers employed endoscopic examination with scoring of tracheal mucus and bronchial septum thickness, bronchoalveolar lavage fluid (BALF) cytology, and bronchial biopsies during spring and summer, using repeated measures ANOVA and Wilcoxon tests to detect statistical differences. Whilst gross endoscopic findings remained stable across seasons, BALF cytology revealed clinically meaningful seasonal shifts: neutrophil percentages were significantly elevated in spring (7.9%) compared with summer (4.5%), and eosinophil counts were notably higher in winter (0.64%) than both spring and summer (0.03–0.14%). Histopathological examination of bronchial tissue showed no significant differences between seasons and failed to correlate with BALF findings, suggesting that subclinical cytological airway changes occur even in outdoor-housed horses without corresponding structural inflammation. These results highlight that environmental and climatic factors produce detectable immunological responses in equine airways regardless of housing type, warranting investigation into which specific seasonal triggers (pollen load, temperature fluctuation, humidity) drive these responses and whether such cyclical inflammation has long-term implications for respiratory performance or disease predisposition.
Read the full abstract on PubMed
Practical Takeaways
- •Outdoor horses experience measurable airway cytological changes across seasons even without clinical signs; practitioners should monitor at-risk horses more closely during spring and winter months
- •Endobronchial biopsies did not add diagnostic value in this cohort and may not be necessary for routine respiratory assessment in asymptomatic horses
- •Seasonal variation in airway immune markers suggests climatic factors influence equine respiratory status—consider this when evaluating recurrent respiratory issues in outdoor-kept horses
Key Findings
- •Neutrophil percentage in BALF was significantly higher in spring (7.9%) than summer (4.5%, P=0.037)
- •Eosinophil count was significantly higher in winter (0.64%) compared to spring (0.03%, P=0.034) and summer (0.14%, P=0.023)
- •Tracheal mucus score and bronchial septum thickness remained stable across all seasons
- •Histopathological findings showed no seasonal differences and did not correlate with BALF cytology results