Salmonella in the lairage of pig slaughterhouses

The purpose of this study was to determine if lairages of pig slaughterhouses can act as a source of contamination of slaughtered pigs with Salmonella. The prevalence and variety of serotypes of Salmonella in the lairages of two pig slaughterhouses were determined, and the efficacy of the usual cleaning and disinfection on the presence of Salmonella was estimated. Lairages of two pig slaughterhouses were sampled three times when pigs were present. Furthermore, these lairages were sampled after the usual cleaning and disinfection, whereas the lairage of one slaughterhouse was sampled an additional time after improved cleaning and disinfection. Samples were collected by swabbing floor and wall surfaces and collecting the residing fluids on the floor throughout the lairage. Salmonella was isolated in 70 to 90% of the samples when pigs were present. The usual cleaning and disinfection reduced the level of contamination with Salmonella to 25% positive samples, whereas improved cleaning and disinfection reduced this level to 10% positive samples. It is concluded that the waiting period in the lairage of at least 2 h contains a substantial risk for slaughter pigs to become infected with Salmonella, especially for pigs originating from Salmonella-free herds. The usual cleaning and disinfection of the lairage were not sufficient to eliminate this risk, whereas an improved procedure for cleaning and disinfection still was unsatisfactory.