Assessment of the impact of age and of blood-derived inflammatory markers in horses with colitis.

Abstract

To determine the impact of age on survival in horses with colitis and to elucidate whether a lower type-1/type-2 cytokine ratio or an exaggerated inflammatory state contribute to reduced survival in aged horses. Part 1: Retrospective cohort analysis. Part 2: Analytic observational study. Part 1: One hundred twenty-four adult horses with colitis. Part 2: Twenty-nine adult horses with new diarrhea onset while hospitalized. Part 1: Patient signalment, select clinicopathological data, diagnoses, treatment, hospitalization length, and invoice were compared between survivors (n=101) and nonsurvivors (n=23). Only age and plasma transfusion retained statistical significance in the final multivariate outcome model, with 8.5 times lower odds of survival in transfused horses (95% confidence interval [CI], 2.6-27.2%). Additionally, the likelihood of nonsurvival increased by 11.8% (95% CI, 4-20.2%) for every year the horse aged (P=0.002). Similarly, geriatric horses (≥20 years) were 15.2 times more likely to die than young-adults (2-12 years, P=0.03), independent of financial investment, documented comorbidities, and duration of hospitalization. Part 2: Select cytokine analyses were performed on serum collected from hospitalized horses within 1hour of diarrhea onset (T0) and 6hours later. At T0, all recorded clinicopathological variables were comparable between geriatric and young-adult horses, suggesting a similar degree of systemic illness. The median concentration of type-2 cytokines interleukin-4 and interleukin-10, and type-1 cytokine interferon-γ did not differ between age groups. Inflammatory cytokines interleukin-6 and tumor necrosis factor-α were significantly higher in geriatric compared to young-adult horses at both sampling time points. Outcome of colitis was less favorable in aging horses and patients receiving a plasma transfusion. Although an exaggerated inflammatory state, based on increased interleukin-6 and tumor necrosis factor-α concentrations, in geriatric horses may contribute to reduced survival, a lower type-1/type-2 cytokines ratio was not identified in our geriatric population.