High prevalence of Salmonella in lymph nodes and tonsils of swine presented for slaughter in Mexico

This study reports the prevalence of culturepositive Salmonella in lymphoid tissues of swine presented for slaughter in two municipal abattoirs in Mexico. Fifty tonsils, and 110 mandibular, 90 mesenteric, and 115 subiliac lymph nodes (LNs), were recovered from 115 pork carcasses sampled across four days during a six-month period in a Merida harvest facility. Additionally, 10 mandibular LNs, 10 subiliac LNs, and 10 tonsils were recovered from 10 pork carcasses in a Cancun facility. The prevalence of Salmonella in the Merida facility was 18.0 [9/50], 12.7 [14/110], 44.4 [40/90], and 10.2% [12/115] for tonsils, mandibular, mesenteric, and subiliac LNs, respectively. In the Cancun abattoir, the prevalence was 40.0 [4/10], 20.0 [2/10], and 20.0% [2/10] for tonsils, mandibular, and mesenteric LNs, respectively. In Merida, values varied significantly across sampling days for all three LN types. These results verify that swine carry Salmonella systemically, posing a potential risk of cross-contamination of pork products for human consumption into which lymphoid tissues may be incorporated.