Detection of bacteraemia and host response in healthy neonatal foals

Reasons for performing the study: Neonatal sepsis is a common problem in foals and is a primary cause of death in the post natal period. Transient bacteraemia and subsequent host responses have not been described in the equine neonate. Objectives: The primary objective of this study was to determine if transient bacteraemia occurs in foals within the first 72h of life. Additional objectives included description of bacterial organisms associated with transient bacteraemia and concurrent cytokine gene expression in healthy foals. Study design: Prospective observational study in healthy foals. Methods: Blood was aseptically collected for bacterial culture from observed spontaneously born foals at birth and 1, 2, 3, 4, 8, 12, 24, 48 and 72h following birth. Samples taken at birth, 4, 12, 24, 48 and 72h were analysed for interferon gamma (IFNγ), interleukin (IL)-1, IL-2, IL-6, IL-8, IL-10, IL-18 and monocyte chemotactic protein 1 (MCP1) cytokine gene expression quantified by RT-PCR. Results: Bacteria were cultured from 9 of 70 samples submitted for blood culture. The positive samples were from 4 of the 7 foals, all of which remained healthy throughout and subsequent to the study. All positive blood cultures were from blood samples obtained at 12h of age or earlier and IL-10 elevation coincided with positive blood cultures in healthy foals. Cytokine gene expression fluctuated with age. Conclusions: Positive blood cultures suggest transient bacteraemia may occur in healthy foals early in the post natal period. Age corrected normal values may be necessary to interpret cytokine concentration in diseased populations.