Association between fungal detection, airways inflammation and diagnosis of moderate to severe asthma in horses.
Authors: Barbazanges, Couroucé, Le Digarcher, Cardwell, Schmitt, Toquet, Lemonnier, Richard
Journal: Equine veterinary journal
Summary
# Editorial Summary Fungal spores are constantly present in equine environments, and whilst their role in severe asthma is well established, uncertainty persists about their significance in mild-to-moderate disease. This prospective cross-sectional study examined 155 horses (35 controls, 85 with mild-to-moderate asthma, and 35 with severe asthma) using both cytology and culture on samples from tracheal wash and bronchoalveolar lavage fluid to determine whether fungal detection correlated with airway inflammation and clinical diagnosis. Fungal prevalence in tracheal wash varied widely (45.7–89.4%) across all groups and proved clinically unhelpful; however, fungal culture from pooled bronchoalveolar lavage fluid revealed significantly higher prevalence in mild-to-moderate asthma horses (31.8%) compared with controls (8.6%), and this finding associated significantly with elevated tracheal mucus scores, high airway neutrophil proportions, and mild-to-moderate asthma diagnosis. Notably, cytological detection of fungi in bronchoalveolar lavage fluid showed the inverse pattern, with lower prevalence in severe asthma cases, suggesting that culture methods—which may capture non-viable or fungal DNA—provide more clinically meaningful results than cytology in the lower respiratory tract. For practitioners, these findings suggest that whilst tracheal wash samples are unreliable for fungal assessment, quantitative culture analysis of bronchoalveolar lavage fluid may help identify fungal contributions to mild-to-moderate airway disease, potentially informing management decisions around environmental control and treatment strategies.
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Practical Takeaways
- •If investigating respiratory disease in horses, obtain BALF and submit for fungal culture rather than relying on tracheal wash or cytology alone, as culture from BALF is most clinically meaningful
- •Fungal airway colonization appears more relevant to mild-moderate asthma than severe asthma, so environmental fungal exposure management may be particularly important for managing intermediate cases
- •High tracheal mucus scores or elevated BALF neutrophils combined with fungal culture positivity support a diagnosis of moderate asthma and warrant investigation of dusty/moldy hay and bedding
Key Findings
- •Fungal detection by culture in BALF was significantly more prevalent in mild-moderate asthma horses (31.8%) than controls (8.6%), but lower in severe asthma (5.7% by cytology)
- •Fungal detection by culture in BALF was associated with high tracheal mucus scores, high neutrophil proportions in BALF, and diagnosis of mild-moderate asthma
- •Fungal detection in tracheal wash by either cytology or culture was uninformative clinically across all groups (45.7-89.4% prevalence)
- •BALF culture, but not cytology, was the preferred method for detecting clinically relevant fungal airway colonization