Variation in the Prevalence of Enteropathogenic Yersinia in Slaughter Pigs from Belgium, Italy, and Spain Pilar Ortiz Martı ´nez, 1 Maria Fredriksson-Ahomaa, 1,2 Adolfo Pallotti, 3 Roberto Rosmini, 3 Kurt Houf, 4 and Hannu Korkeala 1 Abstract Tonsils of 829 fattening pigs originating from Belgium (n ¼ 201), Italy (n ¼ 428), and Spain (n ¼ 200) were collected between 2005 and 2007 to study the prevalence of enteropathogenic Yersinia in slaughter pigs. Isolation of Yersinia enterocolitica and Yersinia pseudotuberculosis was done by selective enrichment and by cold enrichment for 7 and 14 days. Pathogenic Y. enterocolitica and Y. pseudotuberculosis isolates were identified by polymerase chain reaction targeting the chromosomal genes ail and inv, respectively, as well as the plasmid-encoded virF of both species. A significantly higher ( p < 0.001) prevalence of ail-positive Y. enterocolitica in Spain (93%) than in Belgium (44%) or Italy (32%) was observed. virF-positive Y. enterocolitica was present in 77% of ail-positive samples. Bioserotype 4=O:3 was the most common type in all three countries. Bioserotypes 2=O:5 and 3=O:9 were found in Italy (1%) and Belgium (9%), respectively. The prevalence of inv- and virF-positive Y. pseudotuberculosis was 2% and 1% in Belgium and Italy, respectively. Y. pseudotuberculosis was not detected in pigs from Spain. Bioserotypes 1=O:1 (20%), 1=O:2 (20%), and 2=O:3 (60%) were found in Belgium, and 1=O:1 (60%) and 2=O:3 (20%) in Italy. The most efficient method for isolation of Y. enterocolitica was combined cold enrichment for 7 and 14 days; however, the isolation method for Y. pseudotuberculosis was cold enrichment for 14 days. Fattening pigs seem to be an important reservoir of pathogenic Y. enterocolitica in Belgium, Italy, and Spain. Bioserotype 4=O:3 of Y. enterocolitica and bioserotypes 2=O:3 and 1=O:1 of Y. pseudotuberculosis have been shown to predominate. Introduction I n Europe, sporadic yersiniosis cases related to Yersinia enterocolitica in humans are common, whereas outbreaks are rare (Fredriksson-Ahomaa et al., 2009). However, large foodborne outbreaks due to Yersinia pseudotuberculosis have been reported in Finland and Russia, and also an increas- ing number of Y. pseudotuberculosis infections have been ob- served in France ( Jalava et al., 2004, 2006; Nuorti et al., 2004; Anonymous, 2005, 2006; EFSA, 2006; Vincent et al., 2008; Rimhanen-Finne et al., 2009). In Belgium, Italy, and Spain, notification of yersiniosis is not compulsory; thus, no true incidence rates are available from these countries (ECDC, 2009). Infections due to Y. enterocolitica and Y. pseudotuberculosis result in similar manifestations. Diarrhea is a common dis- order among young children. Vomiting, fever, and abdominal pain are also symptoms that occur in yersiniosis patients (Anonymous, 2009a). Enteral yersiniosis in adults often goes unnoticed because of mild symptoms (Fredriksson-Ahomaa et al., 2009; Rastawicki et al., 2009). Reactive arthritis, erythema nodosum, and uveitis are examples of yersiniosis post- infectious sequels (Smego et al., 1999; Fredriksson-Ahomaa et al., 2009). Most human infections are due to Y. enterocolitica of bioserotype 4=O:3 (Anonymous, 2009a). All enteropatho- genic Yersinia strains carry several essential chromosomal virulence genes such as ail and inv. A virulence plasmid (pYV) is needed for full pathogenicity; however, it can be easily lost during culturing (Bottone, 1999). Contaminated pork is a suspected source of human yersiniosis cases (Kanazawa et al., 1974; Tauxe et al., 1987; Fredriksson-Ahomaa et al., 2006; Grahek-Ogden et al., 2007; Fosse et al., 2008). Pigs are an important reservoir of Y. entero- colitica, especially bioserotype 4=O:3, which has a worldwide distribution. They frequently carry this pathogen in tonsils at slaughter (Fredriksson-Ahomaa et al., 2006; Ortiz Martı ´nez et al., 2009). Y. pseudotuberculosis has sporadically been iso- lated from several animal species (Fredriksson-Ahomaa et al., 2009). One potential reservoir for Y. pseudotuberculosis of bioserotype 2=O:3 is slaughter pigs (Kanazawa et al., 1974; 1 Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland. 2 Institute of Food Hygiene, Faculty of Veterinary Medicine, LMU Munich, Munich, Germany. 3 Department of Veterinary Public Health and Animal Pathology, Alma Mater Studiorum, University of Bologna, Bologna, Italy. 4 Department of Veterinary Public Health and Food Safety, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium. FOODBORNE PATHOGENS AND DISEASE Volume 8, Number 3, 2011 ª Mary Ann Liebert, Inc. DOI: 10.1089=fpd.2009.0461 445