Investigation into the prevalence and quantification of Salmonella in cull sow and gilt lymphoid tissues

Abstract

Salmonella is one of the foodborne pathogens that threatens the safety of meat and poultry products. Animals are susceptible to Salmonella contamination during the pre-harvest stage, including transportation lairage, and their carcasses may also become contaminated during slaughter and processing. Analyzing the specific distribution and transmission pathways of Salmonella from the live animal to fabrication and processing can help ensure the safety of meat products. This research investigated the prevalence and quantification of Salmonella in lymph nodes and tonsils of cull sows and gilts during different seasons in the United States. Samples were collected from three pork processing plants. At each sampling visit in 2024, 30 to 35 carcasses were randomly selected from the harvest floor of each plant during the winter, spring, and fall seasons. Seven samples were collected from each carcass, including tonsils and the following lymph nodes: mesenteric, subiliac, superficial inguinal, pre-scapular, axillary, and tracheobronchial. Samples were analyzed using the BAX Salmonella Real-time PCR Assay, and positive samples were quantified for Salmonella by the BAX®-System-SalQuant® method. A total of 1,945 samples were collected, of which 12.5% tested positive for Salmonella. The tissues with the highest prevalence of infection were tonsils (38%, n=284) and mesenteric lymph nodes (31%, n=287). Overall Salmonella prevalence was highest in the fall (15.6%), followed by winter (12.5%), and spring (9.5%). The interaction between sample type and season was significant (P=0.0001). The highest Salmonella prevalence for tonsils (50%, n=96) and mesenteric lymph nodes (42.7%, n=96) occurred during fall, while the highest prevalence for superficial inguinal lymph nodes was observed during winter (28%, n=93). Salmonella prevalence for the remaining sample types (pre-scapular, tracheobronchial, axillary, and subiliac lymph nodes) was less than 4% during all seasons. When considering Salmonella contamination at the carcass level, overall Salmonella prevalence was 60.1% (n=288) and varied by season (P=0.0432). Salmonella carriage in cull sow and gilt carcasses was greatest during fall (70.1%, n=97), and lowest during spring (53.1%, n=98). These findings suggest that seasonal factors have a significant impact on Salmonella contamination in specific tissues from cull sow and gilt carcasses, and therefore, targeted interventions can be implemented to mitigate risk of contamination of pork products during seasons of high prevalence.