Efficacy of the combination of doxycycline and azithromycin for the treatment of foals with mild to moderate bronchopneumonia.
Authors: Wetzig Maria, Venner Monica, Giguère Steeve
Journal: Equine veterinary journal
Summary
# Editorial Summary Rhodococcus equi bronchopneumonia remains a significant challenge in foal populations, and regulatory pressure on rifampin use in some regions necessitates evaluation of alternative antimicrobial combinations. Wetzig and colleagues conducted a randomised, double-blinded controlled trial on a Rhodococcus-endemic farm, assigning 240 foals with mild-to-moderate ultrasonographic pulmonary lesions (10–15 cm) to receive either azithromycin-doxycycline, azithromycin-rifampin, or no treatment. Both treatment groups demonstrated substantially superior recovery rates (azithromycin-doxycycline: 80/81 foals; azithromycin-rifampin: 81/81 foals) compared to untreated controls (57/78 foals), with the difference between active treatments of only 1.2% falling well within the predetermined noninferiority margin of 10%. This finding suggests that doxycycline-azithromycin represents a viable alternative where rifampin use is restricted or unavailable, though practitioners should note the study was conducted on a single endemic farm, and efficacy may vary with local disease epidemiology, antimicrobial resistance patterns, and management practices.
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Practical Takeaways
- •Doxycycline can replace rifampin as a combination partner with azithromycin for treating bronchopneumonia in foals, providing a viable alternative if rifampin becomes unavailable or restricted
- •Both combination treatments showed excellent efficacy (98-100%) compared to no treatment (73%), supporting prompt antimicrobial intervention for foals with pulmonary lesions
- •Individual farm conditions and R. equi prevalence may affect outcomes, so monitor treatment response and adjust protocols based on local epidemiology
Key Findings
- •Azithromycin-doxycycline achieved 98.8% recovery rate (80/81 foals) compared to azithromycin-rifampin at 100% (81/81), with a difference of 1.2% (90% CI: -0.78% to 3.5%)
- •Both treatment combinations were significantly more effective than untreated controls (73% recovery, 57/78 foals)
- •Azithromycin-doxycycline was non-inferior to azithromycin-rifampin within the predetermined 10% non-inferiority margin
- •Results are specific to a single farm endemic for R. equi and may not generalize to other locations