title: Associations between on-farm and slaughter plant detection of Salmonella in market-weight pigs.
abstract: Thirty swine production units in the midwestern United States were studied to assess the relationship of herd-level prevalence of Salmonella on the farm prior to slaughter versus at slaughter. Fecal samples were collected from 30 pigs on each farm within 48 h of slaughter, and 30 ileocecal lymph node samples were collected in the same shipment cohort at slaughter. Samples were cultured by conventional methods, and Salmonella identity was confirmed by serotyping. Overall, 11.7% (n = 105) of the fecal samples and 14.9% (n = 133) of the ileocecal lymph node samples were positive for Salmonella. Seventeen of the farms (56.7%) had one or more positive fecal samples, and 24 (80.0%) had one or more positive ileocecal lymph node samples. Twenty-four recognized serotypes and three additional distinct antigenic types were identified. Among all isolates, 56.5% had serotypes that were duplicated both on the farm and at slaughter for a particular cohort, whereas the remaining samples lacked a duplicate serotype in the other sample type. There was a positive correlation in the prevalence of Salmonella between fecal samples and ileocecal lymph node samples (Spearman's p = 0.75; 95% confidence interval [CI], 0.62 to 0.89). Linear regression analysis was used to identify two farms that biased the regression estimates. Excluding these farms, 62% of the variance in farm slaughter Salmonella prevalence was accounted for by on-farm prevalence. The analyses suggest that the prevalence of Salmonella spp. at slaughter can be predicted from preslaughter on-farm sampling and vice versa.
authors.affiliation: Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA. pbbahnson@wisc.edu
authors.forename: Peter B
authors.initials: PB
authors.lastname: Bahnson
authors.forename: Jae-Yeon
authors.initials: JY
authors.lastname: Kim
authors.forename: Ronald M
authors.initials: RM
authors.lastname: Weigel
authors.forename: Gay Y
authors.initials: GY
authors.lastname: Miller
authors.forename: H Fred
authors.initials: HF
authors.lastname: Troutt
mesh_terms: D000003:Abattoirs / Q000592:standards*; D000818:Animals; D005243:Feces / Q000382:microbiology; D005506:Food Contamination / Q000517:prevention & control*; D005516:Food Microbiology; D015995:Prevalence; D012475:Salmonella / Q000302:isolation & purification*; D012481:Salmonella Infections, Animal / Q000175:diagnosis* / Q000453:epidemiology / Q000382:microbiology; D012703:Serotyping / Q000662:veterinary; D013552:Swine; D013553:Swine Diseases / Q000175:diagnosis* / Q000453:epidemiology / Q000382:microbiology; D014481:United States / Q000453:epidemiology