Influence of On‐farm pig Salmonella status on Salmonella Shedding at Slaughter

Abstract

The risk of Salmonella shedding among pigs at slaughter with regard to their previous on-farm Salmonella status was assessed in a group of pigs from a farm from NE of Spain. A total of 202 pigs that had been serologically monitored monthly during the fattening period and from which mesenteric lymph nodes (MLN) and faecal (SFEC) samples were collected at slaughter for Salmonella isolation were included. A repeated-measures anova was used to assess the relationship between mean OD% values during the fattening period and sampling time and bacteriology on MLN and SFEC. Pigs were also grouped into four groups, that is pigs seronegative during the fattening period and Salmonella negative in MLN (group A; n = 69); pigs seronegative during the fattening period but Salmonella positive in MLN (B; n = 36); pigs seropositive at least once and Salmonella positive in MLN (C; n = 50); and pigs seropositive at least once but Salmonella negative in (D; n = 47). Pigs shedding at slaughter seroconverted much earlier and showed much higher mean OD% values than non-shedders pigs. The proportion of Salmonella shedders in groups A and D was high and similar (26.1% and 29.8%, respectively), but significantly lower than that for groups B and C. The odds of shedding Salmonella for groups B and C were 4.8 (95% CI = 1.5-15.5) and 20.9 (3.7-118) times higher, respectively, when compared to A. It was concluded that a large proportion of Salmonella seronegative pigs may shed Salmonella at slaughter, which would be likely associated to previous exposure with contaminated environments (i.e. transport and lairage). For pigs already infected at farm, the likelihood of shedding Salmonella was much higher and may depend on whether the bacterium has colonized the MLN or not. The odds of shedding Salmonella spp. were always much higher for pigs in which Salmonella was isolated from MLN.

Looking for new approaches for the use of serology in the context of control programmes against pig salmonellosis

“…Farms presenting low OD% values on day 90 would be expected to remain so for the rest of the fattening period if nothing wrong happens during the time remaining before slaughter. But as pigs showing consistent seronegative results during the fattening period may end up shedding Salmonella at slaughter if they are exposed to highly contaminated environments (Casanova‐Higes et al., ), appropriate disinfection of trucks and lairage areas should be guaranteed for these pigs to try to prevent late infections and further shedding. A large‐scale study to confirm the potential of this approach to reduce Salmonella shedding at slaughter is warranted.…”

“…It has been observed that pigs shedding Salmonella at slaughter seroconverted earlier during the fattening period than non‐shedders pigs (Casanova‐Higes, Andrés‐Barranco, & Mainar‐Jaime, ), which may help to predict the risk of shedding at slaughter. Thus, in this study, we assess whether performing on‐farm serology may help to predict shedding at slaughter and, if so, when, during the fattening period, serology would predict it better.…”

Salmonella Surveillance Systems in Swine and Humans in Spain: A Review

“…The Salmonella status of a pig can be monitored through serological tests performed on meat-juice or serum samples [10] or, more frequently, through the bacteriological analysis of faeces collected at either the farm or the slaughterhouse, where mesenteric lymph nodes can be also collected [7]. There are also microbiological tests conducted on meat and carcasses to verify hygiene practices through the food chain, but in the case of positive results it is often not possible to establish whether the tissue contamination originated from an infected pig farm or occurred as a result of a contaminated environment [11] or insufficient hygiene practices during meat processing [12].…”

Molecular Epidemiology and Resistance Profile of Salmonella Isolated from Chicken, Pork and the Environment at Abattoirs and Supermarkets in Chongqing, China

“…Contamination and antimicrobial resistance of Salmonella isolated from food-producing animals is severe worldwide [15], particularly in China [16][17][18]. Furthermore, several studies reported that Salmonella isolates could be recovered from farms, slaughterhouses and retail markets [19,20] and a previous study indicated that Salmonella isolates could transmitted from slaughterhouses to retail markets in pig production chain [17]. However, few studies focused on the comparison of Salmonella contamination in pig and chicken as well as their slaughtering and retail chain.…”