Prevalence and serovars of Salmonella enterica on pig carcasses, slaughtered pigs and the environment of four Spanish slaughterhouses

The purpose of this study was to investigate the prevalence of Salmonella contamination and main serovars in pig slaughterhouses in Spain including carcasses, live animals and the environment. A total of 896 pig carcasses were randomly selected and swabbed before chilling in 3-5 visits to four pig slaughterhouses (A, B, C and D). Salmonella contamination was detected in 39.7% of the carcasses. The prevalence of positive carcasses was similar amongst slaughterhouses but significant differences were observed when taking sampling day into consideration within each of the slaughterhouses. Furthermore, a significant reduction in the prevalence of Salmonella contaminated carcasses (10.8%) was demonstrated in slaughterhouses C and D after chilling and cooling procedures. Sixteen batches of 10 animals were tracked from farm-to-slaughterhouse in slaughterhouses A and B to investigate the relationship between carcass contamination and contamination in live animals entering the slaughterhouse. No difference was found between infected and uninfected animals with respect to Salmonella contamination of the carcass although an increase in Salmonella contamination during the processing of live pigs into pork carcasses was evident. Regarding contamination in the slaughterhouse environment, Salmonella was isolated from most of the evaluated points in the slaughter line of the four studied slaughterhouses. Holding pens were identified as highly contaminated and what is more the ineffectiveness of the routinely cleaning protocols at this level was demonstrated in slaughterhouses C and D. The predominant Salmonella serovars found in carcasses, live pigs entering the slaughterhouse and the environment of the slaughterhouse were S. Typhimurium, S. Rissen, S. Derby and S. 4,[5],12:i:-. The same serovars were found in all the stages supporting the hypothesis that infected pigs are the main source of Salmonella contamination within slaughterhouses. (C) 2011 Elsevier Ltd. All rights reserved.