Salmonella is Present in Multiple Lymph Nodes of Market Hog Carcasses at Slaughter

The presence of Salmonella in lymphoid tissue of market hogs represents a potential risk for the safety of pork products, particularly ground pork. With increased Salmonella testing standards required by the U.S. Department of Agriculture (USDA) on the horizon for the pork industry, it is important to improve understanding of Salmonella contamination within a variety of swine tissues, including lymph nodes. This study was designed to provide preliminary information about Salmonella prevalence in multiple lymph nodes within market hog carcasses at slaughter. From each carcass (n = 50), four lymph nodes were aseptically collected at slaughter: mesenteric, tracheobronchial, inguinal, and subiliac. A total of 197 lymph nodes were analyzed, with an overall Salmonella prevalence of 21.8% (n = 43). Salmonella was detected in the lymph nodes of 62% (n = 31) of carcasses, with 21.6% (n = 11) of carcasses harboring Salmonella in two or more lymph node types. Although not statistically significant (P = 0.1167), Salmonella prevalence did vary based upon lymph node type (mesenteric, 34%; inguinal, 18.4%; subiliac, 18.4%; tracheobronchial, 16.3%). This lymph node mapping study provides preliminary evidence that Salmonella can contaminate lymph nodes throughout swine and may serve as the foundation for larger lymph node mapping studies or intervention strategies at the abattoir.