An updated description of bacterial pneumonia in adult horses and factors associated with death.
Authors: Hallowell Kimberly L, Hepworth-Warren Kate L, Dembek Katarzyna
Journal: Journal of veterinary internal medicine
Summary
# Bacterial Pneumonia in Adult Horses: Updated Clinical Insights and Prognostic Markers Retrospective analysis of 116 adult horses treated for bacterial pneumonia at a single centre has provided contemporary data on clinical presentation, microbial isolates, and mortality predictors—information notably absent from the existing equine literature. *Streptococcus zooepidemicus* dominated isolates (44%), maintaining predictable penicillin susceptibility, whilst *Escherichia coli*, *Klebsiella* spp., and notably *Fusobacterium* spp. (the most common anaerobes at 11%) reflected a shift from older reported prevalence patterns; antimicrobial susceptibilities otherwise varied considerably, limiting broad therapeutic recommendations. Despite 60% of cases having identifiable historical risk factors, fewer than half presented with abnormal vital signs, yet elevated heart rate and serum creatinine at admission significantly increased mortality risk (odds ratios 1.08 and 14.1 respectively), whilst higher lymphocyte counts conferred protective effects—findings concordant with previous literature. The 73% survival rate and observation that 58% of horses required antimicrobial treatment changes highlight the importance of culture-guided therapy and close monitoring of renal function and inflammatory markers during management. For practitioners, this underscores the value of obtaining bacterial cultures early, maintaining awareness of local susceptibility patterns rather than relying on historical data, and recognising tachycardia and azotaemia as significant poor prognostic indicators warranting intensified intervention.
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Practical Takeaways
- •Tachycardia and elevated creatinine at admission are warning signs for poor prognosis in equine pneumonia; close monitoring of these parameters is critical
- •Streptococcus zooepidemicus remains predictably susceptible to penicillin, but broader spectrum coverage may be needed given the diversity of isolates and high rate of treatment changes required
- •Historical risk factors are present in 60% of pneumonia cases—identifying and managing predisposing conditions may improve outcomes
Key Findings
- •Streptococcus zooepidemicus was the most common isolate (44%), followed by E. coli (19%) and Klebsiella spp. (18%)
- •73% of horses survived to discharge; increased heart rate and elevated serum creatinine at presentation increased risk of death
- •58% of horses required at least one change in antimicrobial treatment; 67% received highest-priority critically important antimicrobials
- •Fusobacterium spp. were the most common anaerobic isolates (11%), contrasting with older literature showing a shift in anaerobic bacterial epidemiology