Poultry housing and the persistence and transmission of Salmonella in egg-laying flocks

Authors: Gast, Richard; Garcia, Javier

Submitted to: Journal of Applied Poultry Research
Publication Type: Review Article
Publication Acceptance Date: 5/21/2026
Publication Date: 5/22/2026
Citation: Gast, R.K., Garcia, J.S. 2026. Poultry housing and the persistence and transmission of Salmonella in egg-laying flocks. Journal of Applied Poultry Research. https://doi.org/10.1016/j.japr.2026.100746.
DOI: https://doi.org/10.1016/j.japr.2026.100746

Interpretive Summary: The commercial egg industry is gradually shifting from housing laying hens in cages toward indoor and outdoor cage-free systems. This transition has raised new disease control and food safety challenges for flock managers. This review summarizes current knowledge about how poultry housing systems influence the sources, persistence, and transmission of Salmonella during egg production. Salmonella can be found in a variety of environmental reservoirs in poultry facilities, including dust, manure, flooring substrates, soil, structural surfaces, and a diversity of insects and animals. Salmonella survival is especially likely when moisture levels are high and air movement is low. After Salmonella is introduced into poultry facilities, it can be spread widely throughout flocks by contact of the birds with each other and with their environment. Stocking birds together at high densities, especially when they can move freely and intermingle in shared floor or ground areas, can increase this “horizontal” transmission of infection. Both cage and non-cage systems are characterized by unique risk factors for Salmonella. Hens in cage-free systems have greater exposure to bird and environmental sources of infection, but the stress of being housed in cages may make hens more susceptible to infection. The design and management of egg-laying hen facilities should thus incorporate risk reduction strategies which address the Salmonella risks associated with different housing systems.

Technical Abstract: The ongoing transition of the egg industry toward increased reliance on cage-free and outdoor housing systems has raised new pathogen control and egg safety challenges for flock managers. This review summarizes current knowledge about how poultry housing systems (conventional and non-cage) influence the persistence, environmental reservoirs, and transmission of Salmonella in commercial egg-laying flocks. Consistently across different types of poultry production environments, salmonellae have been shown to persist in dust, manure, flooring substrates, soil, structural surfaces, and diverse biological vectors, Extended Salmonella survival is especially likely under conditions of high moisture and low airflow. The infection of birds via exposure to environmental reservoirs can be magnified by horizontal dissemination within flocks, which can be especially rapid and extensive when birds are stocked at high densities, can move about and intermingle widely, and share common floor or ground areas. Both cage and non-cage systems have characteristic intrinsic Salmonella risk factors: caging may increase stress-related susceptibility to infection, but cage-free systems may facilitate greater opportunities for exposure to other birds and environmental sources. Accordingly, the design and management of facilities for egg production should incorporate Salmonella risk reduction strategies which target both broadly relevant and housing-specific vulnerabilities to bacterial transmission and persistence.