Risk factors at slaughter associated with presence of Salmonella on hog carcasses in Canada.

Despite the application of hazard analysis and critical control point systems at slaughter and during processing, Salmonella contamination is still a significant biological hazard associated with pork products. A better understanding of risk factors in slaughterhouses and of contamination sources is therefore critical to improve control of this bacterium in the abattoirs. The objectives of this study were to identify the risk factors at slaughter that are associated with the presence of Salmonella on hog carcasses and to assess possible sources of contamination. A questionnaire on potential risk factors was developed. Over 7,400 hogs originating from 312 randomly selected production lots were tested. The lots were from 10 different abattoirs located in five different Canadian provinces. At slaughter, blood was collected for serological analysis, and mesenteric lymph nodes (MLN) and carcass swabs were collected for Salmonella analysis. Furthermore, pulsed-field gel electrophoresis was conducted to establish the genetic profiles of selected isolates from carcasses and MLN and to compare these profiles with those recovered from the slaughter environment. Multivariate regression analysis results indicated that the cleanliness of the hogs and the status of the scald water were factors significantly associated with the Salmonella status of the carcasses at the end of the slaughter process. Pulsed-field gel electrophoresis analysis showed that most isolates from carcasses were similar to those from animals (MLN) or the preevisceration environment.