Prevalence of Yersinia enterocolitica and Yersinia pseudotuberculosis in wild boars in the Basque Country, northern Spain

Background: Yersiniosis is a zoonosis widely distributed in Europe and swine carry different serotypes of Yersinia enterocolitica and Y. pseudotuberculosis. The aim of this study was to determine the prevalence of Y. enterocolitica and Y. pseudotuberculosis in wild boars in northern Spain. The blood of wild boars (n = 505) was sampled between 2001 and 2012. Seroprevalence was determined in 490 serum samples with an indirect enzyme-linked immunosorbent assay. Seventy-two of the animals were also examined for the presence of Y. enterocolitica or Y. pseudotuberculosis in the tonsils with real-time polymerase chain reaction. All the tonsils were analysed twice, directly and after cold enrichment in phosphate-buffered saline supplemented with 1 % mannitol and 0.15 % bile salts. Results: Antibodies directed against Y. enterocolitica and Y. pseudotuberculosis were detected in 52.5 % of the animals. Yersinia enterocolitica was detected with real-time polymerase chain reaction in 33.3 % of the wild boars and Y. pseudotuberculosis in 25 %. Significant differences were observed according to the sampling year, and the highest prevalence was during winter and spring. The highest antibody levels and Y. enterocolitica prevalence were observed in mountainous areas at altitudes higher than 600 m, with very cold winters, and with the highest annual rainfall for each dominant climate. Areas with low and medium livestock populations were associated with the highest seroprevalence of Yersinia spp. in wild boars, whereas areas with high ovine populations had the highest prevalence of Y. enterocolitica. Conclusions: This study shows that Y. enterocolitica and Y. pseudotuberculosis are highly prevalent among wild boars in the Basque country, with Y. enterocolitica most prevalent. The risk of infection among wild boars is influenced by the season and the area in which they live.