Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/31/2009
Publication Date: 2/26/2010
Citation: Wang, B., Wesley, I.V., Mckean, J.D., O'Connor, A.M. 2010. Sub-iliac Lymph Nodes at Slaughter Lack Ability to Predict Salmonella-enteric Prevalence for Swine Farms. Foodborne Pathogens and Disease. 7(7):795-800. Interpretive Summary: Salmonella spp. are major human food-borne pathogens causing gastroenteritis resulting in an estimated 1.4 million cases and 500 deaths annually. Salmonella enterica is a frequently reported pathogen correlated with pork consumption. To determine if lymph nodes collected at slaughter would be reliable predictors of on-farm Salmonella status, we sampled feces (n=1,490) and lymph nodes (n=1,739) collected from hogs originating from 24 Midwest farms. Because of the infrequent detection of Salmonella in lymph nodes at slaughter we concluded that this organ is not a reliable predictor of on-farm Salmonella status.
Technical Abstract: 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 or herd was visited for each farm. For each herd, 30 farm fecal samples and 30 sub-iliac lymph nodes from matched pigs were collected. Samples were cultured for Salmonella spp. and serotyped by conventional methods. Overall, 3.4% (51 of 1,490) of farm feces and 0.06% (1 of 1,739) of sub-iliac lymph nodes were Salmonella positive. Nearly 71.4% (15 of 21) of farms had one or more positive fecal samples, and 4.2% (1 of 24) had one or more positive sub-iliac lymph nodes. The median of within-herd 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 of 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 was Derby, followed by Anatum and Typhimurium (Copenhagen). Braenderup was the only serotype recovered from the sub-iliac lymph node. The rare existence of Salmonella in sub-iliac lymph nodes (0.06%) is not a dependable predictor of Salmonella contamination on farm (3.4%).