Veterinarians commonly prescribe antimicrobials to treat equine asthma, despite limited evidence supporting their use. Tracheal wash (TW) bacterial culture results are known to influence antimicrobial prescription decisions.
A retrospective blinded case-control study aimed to determine whether a positive TW bacterial culture in horses with asthma is associated with bronchial infection or colonization, increased bronchial remodeling, and airway inflammation by evaluating the presence of bacteria and airway remodeling in endobronchial biopsies, as well as bronchoalveolar lavage fluid (BALF) cytology and tracheal mucus scores.
The researchers evaluated tracheal wash aerobic bacterial culture, endobronchial biopsies, BALF cytology, and tracheal mucus scores from horses with severe equine asthma (SEA) (n = 13), mild-to-moderate equine asthma (MEA) (n = 9), and control horses (n = 9).
Study Findings
Tracheal wash cultures were positive in 8/13 horses with SEA, 6/9 horses with MEA, and 8/9 control horses. The researchers did not identify bacteria on Gram stains in any endobronchial biopsy samples. Semiquantitative histologic scores from endobronchial biopsies did not differ significantly between asthmatic horses with positive versus negative TW cultures (p = 0.4). Neutrophil percentages in BALF were not significantly different between asthmatic horses with a positive and negative TW culture (p = 0.5). Tracheal mucus scores did not differ between asthmatic horses with positive versus negative TW cultures (p = 0.7).
Bottom Line
A positive bacterial TW culture in horses with asthma is not associated with bronchial infection, bacterial colonization, increased bronchial remodeling, or increased airway inflammation. Therefore, a positive TW culture in these cases does not confirm the presence of a secondary bacterial infection and should not be considered a primary determinant when making treatment decisions for equine asthma.
https://beva.onlinelibrary.wiley.com/doi/10.1002/evj.70157
Related Reading
- Disease Du Jour: Upper Airway Disorders in Horses
- Research Spotlight: Managing Equine Asthma
- Disease Du Jour: Equine Asthma and EIPH
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