Abstract
Endotoxemia is a common and severe disease of horses. Most previous studies have monitored changes caused by a bolus dose of endotoxin over short time periods. We aimed to describe inflammatory responses to endotoxin with inflammatory and hematologic markers monitored over a longer time than has been performed in the past using more prolonged endotoxin exposures. Escherichia coli O55:B5 endotoxin was administered as a 6-hour continuous intravenous infusion of lipopolysaccharide (LPS) to eight horses. Blood cell counts, and prostaglandin F2α -metabolite (PGM), serum amyloid A (SAA), and serum total iron concentrations were monitored for up to 3 or 6days. An immediate and severe decrease in neutrophils and monocytes occurred in all horses, which subsequently changed to a moderate to strong neutrophilia and monocytosis that persisted for more than 78hours postinfusion (PI) of LPS. Lymphocyte and eosinophil numbers decreased gradually and then normalized after 66- and 78-hours PI, respectively. Mild to moderate, biphasic thrombocytopenia occurred. A pronounced, transient increase in PGM occurred between 1 and 7hours, peaking at 2hours. Serum amyloid A began to increase after 6hours PI and remained elevated after 72hours PI. Serum iron was decreased between 6 and 48hours. The clinical signs were most prominent during the first 24hours PI and subsided within 48hours PI. Neutrophilia, monocytoses, and high SAA concentrations were present in horses even after the clinical signs had subsided. Serum iron normalized before SAA. Knowledge of these findings is imperative when interpreting laboratory results in horses with possible endotoxin exposure.
Published Version
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