Study of Salmonella epidemiology and intervention strategies

Human cases of salmonellosis are frequently linked with the consumption of contaminated table eggs. Over the past decade, the incidence of egg-related Salmonella outbreaks has been increasing in Australia. It was recognized that there is a need for an increased understanding of the dynamics of Salmonella through egg production systems with the specific aim of identifying points in production where the risk for egg contamination was the highest.

The first objective of this study was to investigate Salmonella shedding from day old to end of commercial flock life and the effects of egg washing on reducing levels of Salmonella. The primary aim of this objective was to identify points in the life cycle of layer hen flocks when Salmonella contamination occurs and to study the shedding dynamics on farm once the bacteria is detected. An additional aim of this study was to explore the effectiveness of egg washing on the reduction of Salmonella on a commercial grading floor.

The second objective of this study was to investigate the effects of vaccination on Salmonella contamination of table eggs. While layer hens can become infected with many different Salmonella serovars, Salmonella Typhimurium currently represents the greatest food safety risk in Australia. The primary aim of this objective was to determine the efficacy of a commercially available, live attenuated Salmonella Typhimurium vaccine.