Molecular and Cellular Evaluation of Horses With Summer Pasture Associated Asthma Syndrome.
Authors: Sad Eliene Porto, Hess Tanja M, Santos Huarrisson Azevedo, Lessa Daniel Augusto Barroso, Botteon Paulo de Tarso Landgraf
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Summer Pasture-Associated Asthma in Horses Summer pasture-associated asthma represents a significant clinical and economic concern in equine practice, yet its underlying immunological mechanisms remain poorly characterised, particularly in tropical environments. Porto and colleagues analysed bronchoalveolar lavage fluid from 39 pasture-kept horses, comparing cytokine gene expression profiles between clinically healthy animals and those with confirmed asthma using RT-PCR, with particular attention to Th1, Th2, and pro-inflammatory markers. Asthmatic horses demonstrated substantially elevated expression of IL-5 (10.3 ± 1.13 versus 3.27 ± 0.46 in healthy controls), alongside significantly increased IL-1, IL-4, IL-8, and IFN-λ, establishing a clear Th2-mediated allergic inflammatory phenotype; notably, TNF-α expression was suppressed in the asthma group, indicating a chronic rather than acute antigenic response. These findings suggest that summer pasture asthma operates through a predominantly allergic mechanism rather than infectious or endotoxin-driven pathways, implying that management strategies targeting allergen exposure and Th2 suppression may prove more effective than antimicrobial approaches, whilst the dysregulated IL-5 elevation warrants investigation as a potential diagnostic or prognostic biomarker for clinical monitoring and treatment response assessment.
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Practical Takeaways
- •Horses with summer pasture-associated asthma show distinct allergic inflammation patterns; diagnosis and management should focus on allergen avoidance and anti-inflammatory strategies rather than antimicrobial approaches
- •The elevation of IL-5 and other Th2 cytokines suggests that affected horses may benefit from targeted therapeutic interventions aimed at modulating allergic responses
- •Clinicians should recognize that pasture-associated asthma in tropical environments represents a chronic allergic condition requiring environmental and management modifications for long-term control
Key Findings
- •IL-5 gene expression was significantly elevated in asthmatic horses (10.3 ± 1.13) compared to healthy horses (3.27 ± 0.46), indicating a Th2-mediated allergic inflammatory response
- •Higher gene expression of IL-1, IL-4, IL-5, IL-8, and IFN-λ was found in bronchoalveolar lavage fluid of asthmatic horses relative to controls
- •TNF-α was the only downregulated cytokine in asthmatic horses, suggesting a chronic antigenic reaction rather than acute inflammation
- •Pasture-associated equine asthma demonstrates a predominantly allergic inflammatory profile characterized by increased Th2 cytokine expression