Prevalence and Sources of Salmonella Lymph Node Infection in Special-Fed Veal Calves

Abstract

Peripheral lymph nodes have been implicated as potential contaminants of ground beef, yet the source and timing of Salmonella lymph node (LN) infection in cattle is still unclear, limiting targeted intervention. Thus, the aim of this study was to leverage the vertical integration of special-fed veal production to identify preharvest environmental exposures, namely livestock trailers or harvest facility holding pens where calves spend 30 min. to 4 hrs, that result in Salmonella LN infection. Ten cohorts of 80-82 veal calves were followed through the harvest process, with environmental samples collected in barns, livestock trailers, and harvest facility holding pens. Mesenteric lymph nodes from 35 calves were then collected at harvest. An additional 25 prefemoral LNs per cohort were pooled. Twelve instances of matching Salmonella serovar between environmental and calf LN isolates within the same cohort were submitted for whole genome sequencing to determine if said exposures resulted in LN infection. Cohort-level Salmonella mesenteric LN prevalence ranged from 0 (0/35) to 80% (28/35) and pooled prefemoral LNs were positive in 3 out of 10 cohorts. Environmental Salmonella prevalence was 22% (13/60), 74% (59/80), and 93% (74/80) for barns, livestock trailers, and harvest facility holding pens, respectively. Multidrug resistance was exhibited environmental and LN isolates. Four instances of Salmonella transmission from trailers and/or holding pens to calf LNs were supported by sequence data. One instance from the livestock trailer, two instances from holding pens, and one instance from either trailer or holding pens were captured with multiple serovars (Agona, Give, and Muenster) transmitted. Further research should evaluate the extent of environmental Salmonella transmission in cattle and if targeted interventions in trailers or harvest facility holding pens could reduce novel Salmonella LN infection in veal calves prior to harvest.

A survey of antimicrobial use practices on veal farms in the United States

“…Briefly, survey materials (e.g., cover letter, consent statement, questionnaire, postcard to decline participation, prepaid return envelope) were mailed to all formula‐fed veal calf producers within two U.S. production companies ( n = 32 producers in Company 1; n = 70 producers in Company 2) in February and December 2019, respectively. Most of the formula‐fed veal industry in the United States is highly integrated, and companies rely on contract growers to raise calves for veal production (Locke et al, 2022). There are a small number of formula‐fed veal production companies in the United States, and therefore, the two production companies in this study represent a substantial portion of the total production.…”

Multi‐drug resistant Salmonella ser. Dublin cultured from cryopreserved Holstein semen

“…Bacterial culture and salmonella isolation were performed as previously described using standard operating procedures reviewed and accredited by the American Association of Veterinary Laboratory Diagnosticians. 9 The salmonella isolate underwent antimicrobial susceptibility testing (AST) using the broth microdilution technique using the bovine BOPO7F Sensititre plate (Thermo Fisher Scientific), as described by the manufacturer. Minimum inhibitory concentrations were categorised based on Clinical Laboratory Standards Institute (CLSI breakpoints) where available.…”

Healthy carriage of Salmonella within cattle lymph nodes is a key source of ground beef contamination with strains of clinical significance

“…Research in this area is crucial as preventing asymptomatic Salmonella infections in cattle has been ineffective. Increasing evidence has shown that lymph nodes are a significant source of ground beef Salmonella contamination [8][9][10]. However, despite intensive research, little is known about how the pathogen reaches and survives within the lymph nodes of healthy animals.…”