Live Salmonella Typhimurium vaccination of broilers results in lower Salmonella prevalence on carcasses at commercial processing

Authors: COOKSON, KALEN - Zoetis; HOFARCE, CHARLES - Southern Poultry Research, Inc; DA COSTA, MANUEL - Zoetis; SCHAEFFER, JON - Zoetis; JONES, MATTHEW - Southern Poultry Research, Inc; BAXTER, JENNIE - Southern Poultry Research, Inc; BERGHAUS, ROY - University Of Georgia; Cosby, Douglas; Berrang, Mark; McMillan, Elizabeth

Submitted to: Journal of Applied Poultry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/13/2023
Publication Date: 12/13/2023
Citation: Cookson, K., Hofarce, C.L., Da Costa, M., Schaeffer, J.L., Jones, M., Baxter, J.A., Berghaus, R., Cosby, D.E., Berrang, M.E., Mcmillan, E.A. 2023. Live Salmonella Typhimurium vaccination of broilers results in lower Salmonella prevalence on carcasses at commercial processing. Journal of Applied Poultry Research. 33(100382). https://doi.org/10.1016/j.japr.2023.100382.
DOI: https://doi.org/10.1016/j.japr.2023.100382

Interpretive Summary: Salmonellosis continues to be a major concern for human health with S. Enteritidis, Typhimurium, Heidelberg and Infantis being most often recovered from human illness. Salmonella vaccines for broilers have become accepted as an intervention strategy to reduce the levels of these Salmonella serovars on farm. This study looked at a live S. Typhimurium vaccine to reduce colonization, shedding and carcass contamination of broilers. Preliminary trials were conducted on a research farm followed by a large-scale field trial with a poultry integrator. In the preliminary trials, Salmonella levels were significantly lower in the ceca of the vaccinated broiler. In the field trial, significantly fewer carcasses were positive for Salmonella in the vaccinated flocks. The vaccine provided significant protection to reduce Salmonella in broilers.

Technical Abstract: Food safety is a major concern for consumers, regulators, and poultry producers. The top poultry relevant Salmonella serovars of most concern for human health and safety are S. enterica Enteritidis, Typhimurium, Heidelberg and Infantis. An outbreak of poultry related salmonellosis has obvious public health implications. Such an outbreak may also generate millions of negative consumer impressions, significantly disrupt poultry production and reduce producer revenue. Vaccination of broilers against Salmonella is becoming accepted as an intervention to help producers provide a safe and wholesome product to consumers. We tested a live S. Typhimurium vaccine as a means to reduce broiler colonization, shedding and carcass contamination. Two preliminary experiments were conducted in floor pens followed by a large-scale commercial field trial. In all experiments, vaccinated broilers received a live S. Typhimurium vaccine (Poulvac ST) at day of hatch (spray) followed by a booster vaccination in the second week. Control birds were treated with a sham vaccine. In the floor pen experiments, treated and control chicks were challenged with S. Heidelberg either by direct gavage or indirect exposure from gavage pen mate seeders or previously contaminated pine shaving litter. In the floor pen experiments, vaccinated birds were no less likely to be Salmonella positive but carried a significantly lower number of Salmonella cells in the ceca. No effect was noted on production parameters. In the field trial, treated and control birds were exposed to whatever natural Salmonella challenge was present in the 89 flocks enrolled in the study. Broilers were transported to a commercial slaughter/processing facility; carcass rinses were collected at hot rehang and tested for Salmonella. Significantly fewer carcass rinses were Salmonella positive among vaccinated flocks than unvaccinated flocks. Five serovars of Salmonella were detected from untreated broilers while only two (Kentucky and Muenster) were detected in treated broilers. The vaccine provided significant protection without any negative effect on production parameters.