Background: In human medicine, exuberant neutrophil activation is linked to disease severity and poor prognosis. Whether exuberant neutrophil activation contributes to disease severity and non-survival in critically ill foals is unknown. Hypothesis/Objectives: To determine the plasma concentration of neutrophil activation markers (myeloperoxidase (MPO), citrullinated histone 3 (H3cit), and cell-free DNA (cfDNA)) in healthy, sick non-septic (SNS), and septic foals. We hypothesize that septic foals will have increased concentrations of these markers that will be positively associated with non-survival. Animals: 50 foals < 5 days of age classified on admission as healthy (n=5), SNS (sepsis score < 11, n=26), and septic (sepsis score > 12, n=19).
Methods: Prospective, longitudinal study. Blood was collected at admission and 24h for analysis. Plasma concentrations of cfDNA, MPO, and H3Cit were measured longitudinally using colorimetry (MPO), fluorometry (cfDNA), and immunoassay (H3Cit).
Results: cfDNA concentrations were increased in septic foals at admission (3.4 ng/mL) and 24h (1.8 ng/mL) compared to SNS (1.6 ng/mL and 1.0 ng/mL, respectively) and healthy foals (1.2 ng/mL and 0.7 ng/mL, respectively). The difference was not statistically significant. MPO concentrations were higher in SNS foals at admission (33 U/L) and 24 h (36 U/L) compared to septic (29 U/L and 25 U/L, respectively) and healthy foals (20 U/L and 11U/L, respectively). The difference was not statistically significant. Non-survival and H3cit analysis is ongoing.
Conclusions: The cfDNA and MPO concentrations in the plasma is not associated with sepsis score in foals < 5 days of age. Using fluorescence microscopy, current investigations are ongoing to characterize the ability of foal neutrophils to release neutrophil extracellular traps which are the primary source of neutrophil cfDNA and MPO.
