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The aim of this study was to assess the value of deep systemic sub-iliac lymph nodes collected at slaughter as predictors of Salmonella prevalence in live hogs. An observational study was conducted on 24 farms from September 2006 to February 2009. At least one cohort of market-weight pigs was visited for each farm. Within each cohort, 30 farm fecal samples on farm and 30 sub-iliac lymph nodes from matched pigs at slaughter were collected. Samples were cultured for Salmonella enterica and serotyped by conventional methods. Overall, 3.4% (51 of 1490) of farm feces and 0.06% (1 of 1739) of sub-iliac lymph nodes were Salmonella positive; 71.4% (15 of 21) of farms had at least one positive fecal sample, and 4.2% (1 of 24) had at least one positive sub-iliac lymph node. The median within-farm prevalence of Salmonella in farm fecal samples was 1.7%, ranging from 0% to 38.3%; for sub-iliac lymph nodes the median was 0%, ranging from 0% to 1.1%. The median within-cohort prevalence in farm fecal samples was 0%, ranging from 0% to 43.3%; for sub-iliac lymph nodes the median was 0%, ranging from 0% to 4%. The predominant serotype detected was Derby, followed by Anatum and Typhimurium (Copenhagen). Salmonella Braenderup was recovered from the sub-iliac lymph node. The low detection rate of Salmonella in sub-iliac lymph nodes (0.06%) limits its usefulness as a dependable predictor of Salmonella contamination originating on farm (3.4%).

A systematic review was conducted to evaluate the efficacy of vaccination to reduce Salmonella prevalence in market weight finisher swine. A search of online databases and selected conference proceedings was conducted to identify relevant studies. The review process followed relevance screening, methodological quality assessment, and data extraction. Although multiple outcomes were frequently reported, only outcomes describing culture of Salmonella were extracted. Five clinical trials and 23 challenge studies were considered likely relevant to the review as they described vaccination to reduce Salmonella in swine. Five clinical trials reported vaccination was associated with reduced isolation of Salmonella in market weight pigs, however, information required to assess the internal validity of the study was often not described in the manuscripts. All challenge studies assessed vaccine efficacy in pigs aged <15 weeks reducing the relevance of results to the review which focused on market weight pigs. Only five of the 23 challenge studies reported the majority of information necessary to evaluate the quality of vaccine studies. Given large variability in population type, sample size, type of vaccine, dose and dosing regimens, and type of outcomes observed, pooled data analysis was not possible, and therefore, a qualitative synthesis of the studies was conducted. Available evidence suggests that vaccination is associated with reduced Salmonella prevalence in swine at or near harvest; however, this conclusion is based on studies with design and reporting deficiencies that could potentially indicate biases with the outcome.