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

The research is an investigation into whether there’s any spatial or temporal clustering among horses that shed Salmonella krefeld during their time at a veterinary intensive care unit. The findings reveal that while there is significant temporal clustering, there appears to be no significant spatial relationship, suggesting that transmission is not proximity-based.

Methods and Sample Size

• The researchers conducted a retrospective analysis of medical records. Here, they went back to previously collected data and reexamined it to understand the patterns of Salmonella krefeld shedding better.
• The study centered on a sample size of 219 horses. These horses were all housed in the same intensive care unit of a veterinary teaching hospital, for a period of approximately 8 months stretching from October 1991 through May 1992. This allowed for a relatively large and diverse dataset to work with.

Detection of Salmonella krefeld

• Bacteriologic culturing of fecal samples was the primary method used by investigators to identify the presence of Salmonella krefeld. This procedure involves growing bacteria in a nutrient-rich environment, permitting the identification and study of various bacterial strains. It is a widely used method for identifying bacteria in the medical and veterinary fields.
• Out of the 219 horses, 20 were identified as shedding S. krefeld in their feces, which implies that the infection rate was approximately 9%.

Temporal and Spatial Analysis

• The study employed statistical tools such as the scan statistic for temporal analysis and Knox’s method for spatial-temporal clustering. These methods are used to identify patterns or non-random occurrences in the data.
• Significant temporal clustering was observed over periods of 5, 6, 7, and 8 days among the 20 horses, all shedding S. krefeld. This means that these horses were more likely to begin shedding the bacteria around the same time, although the reasons for this could be varied and require further research.
• The temporal-spatial analysis did not reveal any significant distribution. That is, the study didn’t find a pattern suggesting that closer proximity between the horses influenced the transmission of S.krefeld. This opposes the commonly held belief that contagious infections are usually transmitted more frequently between those in close contact.

Conclusions

• The results indicated a significant degree of temporal clustering but not spatial-temporal clustering amongst the horses shedding S. krefeld, suggesting that the means of transmission wasn’t related to proximity between horses.
• The data implies that other factors, such as shared feed, caretaker handling, or other non-proximity related environments, may be responsible for the pattern of transmission observed in this study.