Barbazanges Pauline, Couroucé Anne, Le Digarcher Gabin, Cardwell Jacqueline M, Schmitt Eliott, Toquet Marie-Pierre, Lemonnier Louise C, Richard Eric A
Department of Equine Internal Medicine, Equine Clinic, ONIRIS, National College of Veterinary Medicine, Food Science and Engineering, Nantes, France.
Université de Caen Normandie, BIOTARGEN UR7450, Caen, France.
Equine Vet J. 2025 Nov;57(6):1531-1542. doi: 10.1111/evj.14470. Epub 2025 Jan 29.
Fungi are ubiquitous in horses' environment. Their contribution to the pathophysiology of severe asthma (SA) is acknowledged, while controversies remain for mild-moderate asthma (MA).
We hypothesised that fungi are a risk factor for asthma. Our objective was to compare different combinations of analytical methods (cytology, culture) and sampling sites (tracheal wash (TW), bronchoalveolar lavage fluid (BALF)) in relation to clinical status (control, MA, SA).
Prospective cross-sectional study.
The study population included asymptomatic racing horses in the field and horses referred to the hospital for respiratory investigations. Fungi were detected by cytology and identified by mycology on TW and pooled BALF. Chi-square tests and multivariable logistic regressions were used for prevalence comparison between groups and association with clinical investigations.
In total 155 horses (85 MA, 35 SA and 35 controls) were included in the study. The overall proportions of fungal detection in TW ranged from 45.7% to 89.4% among groups. The prevalence of fungal detection in BALF was significantly lower by cytology for SA (5.7%) than MA horses (23.6%) and significantly higher by culture for MA horses (31.8%) than controls (8.6%). Fungal detection by culture in BALF was significantly associated with high tracheal mucus score, high neutrophil proportions in BALF and diagnosis of MA.
Mycology was only performed in pooled BALF, and environment was not sampled.
Fungi were significantly more prevalent in the airways of MA horses than SA and/or controls. Fungal detection on TW, either by cytology or culture, was uninformative in a clinical context. Fungal detection by culture, but not cytology in BALF was associated with MA.
