Changing policy to treat foals with Rhodococcus equi pneumonia in the later course of disease decreases antimicrobial usage without increasing mortality rate.
Authors: Arnold-Lehna Denise, Venner Monica, Berghaus Londa J, Berghaus Roy, Giguère Steeve
Journal: Equine veterinary journal
Summary
# Editorial Summary: Targeted Treatment of Rhodococcus equi Pneumonia in Foals Rhodococcus equi pneumonia remains a significant cause of morbidity and mortality in foal populations, yet uncertainty persists around optimal treatment thresholds, particularly given contemporary concerns about antimicrobial stewardship in equine practice. This retrospective analysis of over 600 foals annually (2008–2016) examined whether restricting antibiotic therapy to foals with more extensive pulmonary involvement could reduce drug exposure without compromising outcomes. The authors employed weekly clinical monitoring, haematology, and ultrasonographic assessment to quantify pulmonary abscessation using an 'abscess score'; when treatment protocols shifted in 2012 to target only larger lesions (median abscess score increased from 4 to 11.5 cm), antimicrobial usage among affected foals fell from 81.5% to 50.9%, yet mortality remained statistically unchanged at approximately 0.5% across both periods. These findings suggest that selective, lesion-size-based treatment criteria can substantially reduce unnecessary antibiotic exposure without compromising foal survival, supporting a more nuanced clinical approach than treating all confirmed cases—a distinction particularly relevant as the equine industry faces increasing pressure to combat antimicrobial resistance whilst maintaining therapeutic efficacy.
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Practical Takeaways
- •Withholding antibiotic treatment for foals with small pulmonary lesions on ultrasound does not increase mortality risk and significantly reduces unnecessary antimicrobial exposure
- •Use of serial ultrasonographic monitoring to measure abscess burden provides objective criteria for initiating treatment in suspected R. equi cases rather than treating all cases empirically
- •This evidence supports selective treatment strategies to combat antimicrobial resistance while maintaining equivalent safety outcomes in foal pneumonia management
Key Findings
- •Antibiotic treatment was reduced from 81.5% of foals with R. equi pneumonia (2008-2011) to 50.9% (2012-2016) by implementing selective treatment criteria based on abscess size
- •Median abscess score at treatment initiation increased from 4 cm² to 11.5 cm² between the two periods without changing treatment thresholds
- •Mortality rate from R. equi pneumonia remained unchanged between periods (0.4% vs 0.6%, P=0.6), indicating delayed treatment did not compromise outcomes
- •Targeted treatment protocols substantially decreased antimicrobial usage while maintaining equivalent foal survival rates