Analysis of spatial and temporal clustering of horses with Salmonella krefeld in an intensive care unit of a veterinary hospital.

OBJECTIVE

To determine whether clustering existed in the spatial or temporal distribution of horses that shed Salmonella krefeld in their feces during hospitalization.

DESIGN

Retrospective analysis of medical records.

ANIMALS

219 horses housed in the intensive care unit of a veterinary medical teaching hospital from October 1991 through May 1992.

PROCEDURE

Bacteriologic culturing of fecal samples was used to identify horses shedding S krefeld. For affected horses, the scan statistic was used to analyze temporal clustering, and Knox's method was used to analyze temporal-spatial clustering.

RESULTS

20 horses were identified as shedding S krefeld in their feces. Significant temporal clustering of affected horses was observed for periods of 5, 6, 7, and 8 days. Temporal-spatial analysis did not detect a significant distribution for any combination of time and distance among affected horses.

CLINICAL IMPLICATIONS

Detection of temporal clustering and concurrent random temporal-spatial distribution of affected horses suggested that affected horses were grouped in time, but means of transmission was not related to proximity between horses.