AAAP: Salmonella control strategies
Biosecurity and poultry house management are essential foundations for Salmonella control
24 November 2025
3 minute read
By: Editor's note: following is from presentations at the 2025 annual meeting of the American Association of Avian Pathologists.
Ken Macklin, Mississippi State University, USA, said that Salmonella continues to pose a major challenge to the poultry industry, with official reports of some 1.35 million illnesses, 26,500 hospitalizations, and 420 deaths in the US each year. In response, USDA’s Food Safety and Inspection Service (FSIS) released a proposed framework that places greater emphasis on reducing Salmonella at the preharvest stage. While this regulatory spotlight is relatively new, the poultry industry and research community have long been exploring ways to minimize Salmonella on the farm.
Preharvest intervention strategies include a broad range of tools—feed additives (such as prebiotics, probiotics, phytogenics, and organic acids), water treatments, dietary adjustments, vaccination, and improved flock and litter management.
Sound biosecurity and effective poultry house management remain essential foundations for control. While no single approach offers a complete solution, integrated strategies that combine multiple interventions show strong potential in reducing the salmonella load before birds get processed.
Salmonella in layers
Richard Gast and colleagues at the USDA-Agriculture Research Station in Athens, Georgia, USA, and Purdue University, Indiana, USA, studied the horizontal transmission of Salmonella Enteritidis (SE) within cage-free laying flocks. In one experiment, 1/3 of layer pullets were orally inoculated with SE at either 9 weeks or 15 weeks of age. One to two weeks later, samples of liver, spleen, and intestines were collected from uninoculated (contact-exposed) birds and cultured for SE detection. SE was isolated significantly more often from internal organs after infection at 15 weeks than at 9 weeks (64% vs 22%).
In another experiment, different proportions of 15-week-old pullets (1/3, 1/6, and 1/12) were orally inoculated, and internal organ samples were collected from uninoculated birds 2 weeks later. Also, 5 types of environmental samples (wall dust swab, nest box swab, perch swab, flooring substrate drag swab, and flooring substrate composite) were collected at intervals. The frequencies of SE recovery from both environmental samples and internal organs after inoculation of 1/3 of pullets (97% and 75%, respectively) were significantly greater than after infection of 1/6 of pullets (78% and 58%) and further decreases in SE recovery were observed for inoculation at a 1/12 proportion (10% of environmental samples and 18% of organs).
Flooring substrate composites were the most efficient environmental samples (72% positive) and flooring substrate drag swabs (53% positive) were least efficient. These results suggest that environmental contamination may contribute to horizontal transmission of SE infections among pullets in cage-free housing and infections introduced into flocks during the later stages of pullet rearing may have greater potential to spread before egg production begins.
Vaccination strategies against Salmonella
Charles Hofacre, Southern Poultry Research Group, USA, noted that Salmonella control is important for all segments of the commercial poultry industry: broilers, turkeys, breeders, and commercial layers. The goal for broilers and commercial turkeys is not eradication but reduction. For commercial layers, the goal is complete prevention of shedding of Salmonella Enteritidis (SE) to ensure compliance with the FDA “Egg Rule.” To be successful, producers still need to utilize multiple interventions to lower the amount or load of Salmonella.
Vaccination is one of the tools that can be utilized to increase resistance to colonization of Salmonella spp. from the birds’ feed or environment. Also, vaccination can be a very targeted tool to decrease the shedding of particular Salmonella serovars from one generation to the next.
Other researchers (Holt et al.) found that Salmonella vaccination decreases the ability of SE to survive in eggs, thus reducing the risk to consumers from commercial layer eggs. Vaccination of breeders (broiler, turkey, layer) will use a combination of commercially available live vaccine and/or inactivated vaccines. Live vaccines have been shown to provide protection to multiple Salmonella serotypes while inactivated vaccines have historically been protective to the Salmonella serotype contained in that vaccine.
Traditionally, inactivated vaccines have been oil emulsion adjuvants and injected into breeder hens. The use of both live attenuated and inactivated vaccines is one of the key tools in any Salmonella control strategy.
