Detection of bacteraemia and host response in healthy neonatal foals.
Authors: Hackett E S, Lunn D P, Ferris R A, Horohov D W, Lappin M R, McCue P M
Journal: Equine veterinary journal
Summary
# Editorial Summary: Detection of bacteraemia and host response in healthy neonatal foals Neonatal sepsis remains a leading cause of mortality in foals, yet little has been documented about transient bacteraemia in healthy neonates during the critical early post-natal period. Hackett and colleagues conducted a prospective observational study on seven spontaneously born foals, collecting blood samples aseptically from birth through 72 hours of age and culturing for bacteria at nine timepoints, whilst simultaneously measuring cytokine gene expression (IFN-γ, IL-1, IL-2, IL-6, IL-8, IL-10, IL-18 and MCP1) via RT-PCR. Bacteria were recovered from nine of 70 samples, originating from four of the seven foals, yet all animals remained clinically healthy throughout the study period; notably, all positive cultures occurred before or at 12 hours of age, and elevated IL-10 gene expression coincided with bacteraemia detection. These findings suggest that transient bacteraemia is a normal physiological occurrence in healthy foals during the immediate post-natal period rather than an indicator of disease, with IL-10 potentially serving as a marker of this response. For equine practitioners, establishing age-corrected baseline cytokine values in healthy populations is essential for accurately identifying pathological sepsis in sick foals, as current reference ranges may not account for the dynamic immunological changes occurring in the first days of life.
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Practical Takeaways
- •Transient bacteraemia appears to be a normal occurrence in early neonatal foal life; presence of bacteria in blood cultures at <12 hours of age does not necessarily indicate sepsis in a clinically healthy foal
- •Cytokine expression patterns change with age in foals, so interpretation of immune markers must be age-adjusted to avoid misdiagnosis of healthy neonates as septic
- •Monitor clinical signs rather than relying solely on positive blood cultures in the first 12 hours post-birth when determining if a healthy foal requires sepsis treatment
Key Findings
- •Transient bacteraemia occurred in 4 of 7 healthy foals (57%), with positive blood cultures from 9 of 70 samples
- •All positive blood cultures were detected at 12 hours of age or earlier in the post-natal period
- •IL-10 cytokine elevation coincided with positive blood cultures in healthy foals
- •All foals with transient bacteraemia remained healthy throughout and after the study period, suggesting the immune system effectively controlled early bacteraemia