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The prevalence of human pathogenic Yersinia enterocolitica was determined in tonsil and intestinal content samples from 388 healthy fattening pigs at the four biggest Finnish slaughterhouses. These slaughterhouses process 73% of pigs in Finland. Tonsil samples were tested by PCR targeted for yadA, and intestinal samples were cultured. All pathogenic Y. enterocolitica isolates represented bioserotype 4/O:3. The prevalence of Y. enterocolitica in tonsil samples was 60% (95% confidence limit, 55.4 to 65.1%), and its prevalence in intestinal samples was 26% (95% confidence limit, 22.1 to 31.2%). The prevalence of Y. enterocolitica in tonsil and intestinal samples varied between the four slaughterhouses. The tonsil prevalence of Y. enterocolitica was higher in slaughterhouse B, and the prevalence in intestinal content was higher in slaughterhouse C. There were more positive results in both tonsil and intestinal samples in pigs coming from fattening farms than in pigs coming from farrowing-and-fattening farms. A seasonal variation was observed in the prevalence of Y. enterocolitica in intestinal samples, with the highest prevalence during July and August, but no seasonal variation was detected in tonsil samples. [ABSTRACT FROM AUTHOR]

To evaluate the effectiveness of bagging of the rectum in mitigating the contamination of carcasses with enteropathogenic Yersinia at the slaughterhouse and to estimate the hidden prevalences of these pathogens in different farm types and capacities, samples from pigs, carcasses, and slaughterhouse environment were collected, and a Bayesian probability model was constructed. In addition, the contamination routes were studied with molecular typing of the isolated strains. According to the model, bagging of the rectum reduced carcass contamination significantly with pathogenic Yersinia enterocolitica, but not with Yersinia pseudotuberculosis, and alone it was insufficient to completely prevent the carcass contamination with enteropathogenic Yersinia. The hidden prevalence of pathogenic Y. enterocolitica was higher at high production capacity than it was in low production capacity, but the 95 % credible intervals overlapped. Slaughterhouse environments can contaminate carcasses with enteropathogenic Yersinia, but the plausible main contamination source is the pig carrying the pathogen.