Temporal Sampling of Commercial Turkey Flocks Highlights Challenges of Preharvest Salmonella enterica Monitoring

Reducing Salmonella in turkey meat is a key focus of industry efforts to improve food safety, necessitating the identification of a reproducible, affordable, and feasible surveillance sample and timepoint to indicate Salmonella at processing. In this study, bootsocks, paw swabs, and vent swabs were evaluated at placement, brood move, pretransport, and harvest to compare and assess Salmonella prevalence, load, and serovars in 26 turkey flocks. Prevalence was determined by culture and qPCR, load via qPCR, and serovars using CRISPR-SeroSeq. While prevalence varied between sampling timepoints and methods (both p < 0.05, Pearson X²), bootsock prevalence was highest (58.2%), and the greatest incidence was at placement (80.1%). Prevalence was lowest at pretransport (20.1%) and in vent swabs (34.5%). At harvest, prevalence increased to 34.6%. In 58.5% of preharvest and 82.5% of harvest samples, Salmonella loads were unquantifiable (<1 log₁₀ CFU/mL). The greatest number of samples was quantified at placement where load was 1-6.19 log₁₀ CFU/mL. Salmonella load decreased through pretransport and then increased at harvest (1-4 log₁₀ CFU/mL). Sixteen serovars were detected from 25 flocks. Bootsock had the highest complexity (avg. 2.4 serovars/sample; 77.8% multiserovar) while vent swabs had the lowest (1.3, 25.0%). Placement was the most complex (2.3, 69.8%), while pretransport (1.0, 0.0%) and harvest (1.1, 6.7%) samples were the least complex. In 11 flocks, harvest serovars were unique from those on farm. In 20 flocks, multiple sample types were necessary to detect all serovars at a timepoint. This study emphasizes that sampling methods and timepoints influence Salmonella detection, load, and serovars. Bootsocks were the best sample, but no timepoint was identified that accurately anticipated Salmonella profiles found at processing. This study highlights challenges of Salmonella surveillance sampling in turkey production and temporal changes to Salmonella populations within flocks.