Chapter 2 - Microbiology of Shell Egg Production in the United States

Abstract

A significant proportion of human illnesses caused by Salmonella is linked to the consumption of contaminated eggs. Substantial government and industry resources have been committed to comprehensive Salmonella testing and risk reduction programs for commercial egg-laying flocks. The implementation of multiple interventions throughout the egg production cycle is recognized as the most effective strategy for controlling Salmonella in poultry. Although egg-transmitted disease is principally attributed to Salmonella Enteritidis, other serovars (notably Salmonella Heidelberg and Salmonella Typhimurium) have also been implicated. Eggs typically become contaminated with S. Enteritidis in their edible interior contents due to colonization of reproductive tissues (ovary and oviduct) in systemically infected hens, although bacterial penetration through eggshells following external deposition is also possible. Controlling storage temperatures is critical for restricting Salmonella growth inside eggs. Environmental conditions in poultry housing facilities directly impact opportunities for Salmonella introduction, transmission, and persistence in laying flocks. Many environmental parameters are influenced by the production housing systems used in the modern commercial egg industry, and each system is characterized by unique risk factors and management challenges.