Abstract
Field studies on Salmonella infection in suckling piglets are scarce due to the intrinsic difficulties of collecting proper samples (i.e. tonsils or mesenteric lymph nodes), and most of them rely on the analysis of rectal swabs that limit their accuracy. We used 495 slaughtered 4-weeks-old male piglets intended for human consumption from 5 Salmonella-seropositive breeding farms to collect gastrointestinal packages and perform a thorough detection of Salmonella on mesenteric lymph nodes and intestinal content. The overall prevalence of both infection and shedding was high (≈ 36%) indicating that piglets played an active role in Salmonella maintenance in the farms. Major serotypes found in piglets included 4,[5],12:i: (35.4%), Rissen (17.1%), Derby (10.9%) and Bovismorbificans (10.3%). In most of the infected animals (72.8%) the same serotype was found in mesenteric lymph nodes and feces. Significant higher ELISA OD% values were found in meat juice samples from non-infected piglets compared to infected ones (median OD% of 12.0 and 17.3, respectively; P = 0.002) suggesting some protective effect of sow’s colostrum. Salmonella was also isolated from feces from weaned sows contemporary of the slaughtered piglets, and 89% of the serotypes identified in sows were also detected in piglets. Pulsed field gel electrophoresis analyses showed that 75% of the piglet isolates that were compared to those of sows were related to them, suggesting the circulation of Salmonella strains between sows and piglets. It appears that improving piglet colostrum intake along with the reduction of the shedding in sows may favor the control of Salmonella infection in breeding farms.
Highlights
Salmonellosis is the second most commonly reported bacterial foodborne infection in humans in the European Union (EU) after campylobacteriosis [1]
The dynamics of Salmonella infection has been extensively studied during the latter period [3,4,5,6,7,8], as fattening pigs are intended for human consumption and are considered the main source of Salmonella carcass contamination at slaughter [9, 10]
Isolates meeting the following criteria were considered for analysis: 1. For the assessment of the relationship of Salmonella infection and shedding in piglets: when the same Salmonella serotype was isolated from mesenteric lymph nodes (MLN) and intestinal content (IC) samples from the same piglet, these two isolates were analyzed by pulsed-field gel electrophoresis (PFGE) analysis
Summary
Salmonellosis is the second most commonly reported bacterial foodborne infection in humans in the European Union (EU) after campylobacteriosis [1]. The dynamics of Salmonella infection has been extensively studied during the latter period [3,4,5,6,7,8], as fattening pigs are intended for human consumption and are considered the main source of Salmonella carcass contamination at slaughter [9, 10]. During this period there are multiple opportunities to collect samples either on farm (blood and feces) or at slaughter (blood, meat juice, gastrointestinal content, Casanova‐Higes et al Vet Res (2019) 50:45 mesenteric lymph nodes, tonsils or the carcasses). All these results should help to shed more light on the risk factors for transmission of this infection within infected breeding farms and design better methods for its control
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