Influence of fecal shedding of Salmonella organisms on mortality in hospitalized horses

Abstract

Objectives: To predict mortality of horses by use of clinical data from the first day of hospitalization, to determine whether fecal shedding of Salmonella organisms is related to severity of clinical disease, and to determine the impact of fecal shedding of Salmonella organisms on mortality.

Design: Prospective study.

Animals: 1,446 hospitalized horses.

Procedure: Medical information was obtained from horses hospitalized in an intensive care unit or isolation facility during a 4.5-year period. A model was created to predict mortality, using covariates determined on the day of admission. Predicted mortality provided a measure of clinical condition. Predicted mortality was compared between horses that were and were not shedding Salmonella organisms in their feces to determine whether shedding was associated with severity of disease. Predicted and observed mortality between horses were also compared to evaluate the association between fecal shedding of Salmonella organisms and mortality.

Results: 92 horses were identified as shedding Salmonella organisms. In a multivariable model, 4 variables (heart rate, respiratory rate, rectal temperature, and clinical management) were associated with mortality. A higher predicted probability of death was observed in horses that shed Salmonella krefeld or more than 1 serotype. Relative risk (RR) of mortality was high for horses shedding S typhimurium (RR, 1.94; 95% confidence interval, 1.04 to 3.59) and multiple serotypes (RR, 4.75; 95% confidence interval, 2.29 to 9.84). When the clinical condition (i.e., prior predicted probability of death) was taken into consideration, fecal shedding of Salmonella organisms was not significantly associated with mortality.

Clinical implications: In this horse population, fecal shedding of S krefeld was associated with more severe clinical conditions at the time of admission; however, fecal shedding of Salmonella organisms during hospitalization did not alter predicted mortality.