Occurrence and significance of Salmonella in laboratory samples obtained after normal slaughter of pigs

The authors analyzed Salmonella positivity in pig slaughterhouse samples se nt for additional laboratory examination between 1978-1997. The prevalence of Salmonella positivity was 2.2% (213 out of 10,014) in samples taken duri ng meat inspection after emergency slaughter whereas it was 0.54% (65 out o f 11,933) following normal slaughter. The detailed results of the second category are presented in this article. The yearly distribution of Salmonella occurrence ranged between 0-13. These were 18 serotypes occurring overall with S typhisuis (23.1%), S. choleraes uis (20%) being the most common serotypes before other serotypes not adapte d to swine. The latter were most commonly represented by S. derby, S. infan tis and 'R' type Salmonella. There was a non significant trend for S. typhi suis and S. choleraesuis to decrease and for not adapted serotypes to incre ase ia prevalence with time. Samples from viscera (spleen, liver, kidney) were infected with Salmonella relatively commonly (23.07%), more so than muscle and lymph mode samples re presenting,meat". The most common source of Salmonella infection were patho logical lesions (overwhelmingly abscesses). Generally, there tvas only a si ngle infected organ, two organs were infected in 7.69% of all cases, three in 4.62%, six in 1.54%, On the basis of the lesions, nine pigs out of 65 th at were infected with Salmonella were acutely hi the rest had lesions indic ative of chronic processes dominated by abscesses and chronic inflammatory changes (Table 1.) During splitting and cutting, incised Salmonella-infected abscesses may cau se smear contamination of the cutting line and the carcasses which can be l imited by strict adherence to HACCP rules. Food safety is increased if the viscera of the pigs separated for veterinary examination are carefully trim med away, are declared unfit for human consumption and are condemned.In mod ern slaughterhouses with integrated meat inspection and consistent applicat ion of HACCP principles slaughter animals diseased due to Salmonella infect ion play a secondary role in contaminating the premises. The importance of diseases of slaughter animals due to Salmonella infection decreased compare d with previous years and the problem became manageable. The main threat fo r slaughter and cutting plants today Is thus the presence of asymptomatic c arriers of Salmonella among slaughter animals.