Quantitative examination of Salmonella spp. in the lairage environment of a pig abattoir

One of the initial sources of Salmonella spp. and other bacterial pathogens at the abattoir is the carrier pig. In the absence of effective cleaning and disinfection measures, such animals may contaminate the lairage environment, which may act as a significant source of infection for incoming non-infected animals. The objectives of this study were to quantify the levels of Salmonella spp. in the lairage of a large pig abattoir and to compare the effect on environmental contamination levels with Salmonella spp. of the cleaning procedures carried out daily to those undertaken weekly. A total of 359 swabs were collected from lairage pen floors at three timepoints throughout the course of two slaughter days. All samples were analyzed quantitatively. On day 1, Monday, following weekly cleaning and disinfection, 6% of the 179 floor swabs taken were positive for Salmonella spp. On day 2, Thursday, at the end of the slaughter week, when lairage pens were subjected to high-pressure cold water washing between batches of pigs, 44% of the 180 floor swabs taken were positive for Salmonella spp. Quantitative analysis revealed that the median numbers of salmonellae detected following weekly cleaning and disinfection were similar to 1.8 organisms/100cm(2). The numbers of salmonellae detected on day 2 were approximately 8 organisms/100cm(2). The most prevalent serotype isolated in this study was S. Typhimurium (42%). Phage types DT12, DT104b, and U302 comprised the majority of phage types identified. These results highlight the need to develop effective intervention measures to control the spread of Salmonella spp. in the preslaughter environment.