Prevalence of enteropathogenic Yersinia in pigs from different European countries and contamination in the pork production chain

Enteropathogenic Yersinia can enter the food chain and infect consumers via pork. Although yersiniosis is the third most common bacterial enteric disease in Europe, there has been a lack of studies concerning the prevalence and bioserotypes of enteropathogenic Yersinia in pigs from European countries. This study was conducted in order to gain further information on the prevalence of enteropathogenic Yersinia in pigs from separate European countries. In order to examine the transmission routes of enteropathogenic Yersinia in the pork production chain from the farm to the slaughterhouse, enteropathogenic Yersinia strains were characterised in Finland by PFGE. Because the conditions on a farm can affect the prevalence of enteropathogenic Yersinia, possible farm factors associated with Yersinia prevalence were also investigated by using a questionnaire and on-farm observations. Pathogenic Yersinia enterocolitica was a common finding among all European countries included in the study. The highest (93%) and lowest (32%) prevalence of pathogenic Y. enterocolitica was observed among pigs from Spain and Italy, respectively. The prevalence in Estonia and Latvia in Northern Europe was lower than in Spain, but still at a high level of 89% and 64%, respectively, among pigs. The Leningrad region of Russia showed one of the lowest prevalence among the studied European countries. In addition, pathogenic Y. enterocolitica was present among 44% of pigs from Belgium and England or Central Europe and Western, respectively. The highest prevalence of Yersinia pseudotuberculosis was detected among English pigs (18%). Furthermore, 7%, 5% and 2% of pigs examined from the Leningrad region of Russia, Latvia and Belgium, respectively, and 1% in Italy and Estonia were positive for Y. pseudotuberculosis. Cold enrichment for 7 and 14 days combined was a more efficient method to isolate enteropathogenic Yersinia when compared to selective enrichment. The most common human pathogenic bioserotype 4/O:3 of Y. enterocolitica was also present in all studied European countries, predominating among Belgian (91%), Estonian (100%), Italian (99%), Latvian (100%), Russian (100%) and Spanish (100%) pigs, but not among English pigs (11%). In England, the most common human pathogenic bioserotypes of Y. enterocolitica were 2/O:9 (33%) and 2/O:5 (26%). Y. enterocolitica bioserotype 2/O:5 was also found among Italian (1%) pigs. In addition, less frequently isolated European human pathogenic bioserotypes 2/O:3 and 3/O:3 were respectively found in 7% and 0.3% of pigs from England, and 3/O:9 in 9% of pigs from Belgium. Bioserotype 2/O:3 of Y. pseudotuberculosis, the most commonly isolated type in pigs in Finland, predominated among Belgian (60%), English (34%), Estonian (100%), Latvian (100%) and Russian (100%) pigs, and was present among Italian pigs (20%). Bioserotypes such as 1/O:1, 1/O:2, 1/O:3, 1/O:4, 2/O:1, 2/O:5 and 3/O:3 were also found. Y. pseudotuberculosis 1/O:1 was predominant in Italy (60%), and also found in England (26%) and Belgium (20%). Y. pseudotuberculosis 1/O:2 was isolated from Belgian (20%) and English (7%) pigs. Bioserotypes 1/O:3 (5%), 1/O:4 (24%), 2/O:1 (3%), 2/O:5 (1%) and 3/O:3 (1%) were additionally found in England, showing the highest diversity of different bioserotypes in this country. In Finland, only bioserotype 4/O:3 of Y. enterocolitica and 2/O:3 of Y. pseudotuberculosis were isolated. Undistinguishable genotypes of Y. enterocolitica and Y. pseudotuberculosis isolated from a farm and a slaughterhouse indicated that carcass contamination has its origin on the farm and enteropathogenic Yersinia is transported with the pig to the slaughterhouse. Based on Y. enterocolitica genotypes, Y. enterocolitica-positive pigs are contaminating pluck sets, and pluck sets can also be contaminated with Y. enterocolitica from other sources in the slaughterhouse. Factors associated with the high prevalence of Y. enterocolitica on farms according to correlation and two-level logistic regression analysis were drinking from a nipple, the absence of coarse feed or bedding for slaughter pigs, and no access of pest animals to the pig house. Those farms with an organic or low-production capacity showed a lower prevalence than high-production capacity conventional farms. Farm factors associated with the presence of Y. pseudotuberculosis in Finnish farms were contact with pest animals and the outside environment and a rise in the number of pigs on the farm. Organic production farms had a higher prevalence than conventional farms.Yersinioosi on kolmanneksi tärkein suoliston infektiotauti Euroopassa aiheuttaen ihmisille terveysongelmia. Siat toimivat Yersinian varastoina, mutta tiedot Yersinian esiintyvyydestä ja sen eri serotyypeistä Euroopan eri alueilla on puutteellista. Tässä työssä tutkittiin enteropatogeenisen Yersinia enterocolitican ja Yersinia pseudotuberculosiksen esiintyvyyttä useissa Euroopan maissa. Lisäksi tutkittiin patogeenisen Yersinian siirtymistä ruokaketjussa tuottajalta teurastamolle Suomessa sekä tuottajatilojen olosuhteiden vaikutusta Yersinian esiintyvyyteen. Yersinia määritykset tehtiin yli kahdesta tuhannesta näytteestä, mitkä olivat peräisin kahdeksasta eri Euroopan maasta. Enteropatogeenisten Yersinia-kantojen eristykseen käytettiin neljää eri menetelmää, joita myös verrattiin keskenään. Suurin patogeenisen Y. enterocolitican esiintyvyys oli Espanjassa 93% ja Virossa 89%. Seuraavaksi suurimmat esiintyvyydet olivat Latviassa 64%, Belgiassa 44% ja Englannissa 44%. Pienin esiintyvyys oli Italiassa 32%. Patogeenisen Y. pseudotuberculosiksen esiintyvyys sioissa Englannissa oli suurin 18% ja sen esiintyvyys Venäjällä oli 7%, Latviassa 5%, Belgiassa 2%, sekä Virossa ja Italiassa 1%. Yleisin Y. enterocolitican bioserotyyppi oli 4/O:3. Y. enterocolitica 4/O:3:n esiintyvyys sioissa oli 100% Espanjassa, Latviassa, Suomessa, Venäjällä ja Virossa, Italiassa 99%, Belgiassa 91%, mutta Englannissa vain 11% oli tätä serotyyppiä. Englannissa oli suurin biodiversiteetti eri serotyyppejä. Yleisimmät ihmiselle patogeeniset Y. enterocolitican bioserotyypit Englannissa olivat 2/O:9 (33% eristetyistä kannoista) ja 2/O:5 (26%). Virolaisissa, latvialaisissa ja venäläisissä sioista löydettiin vain Y. pseudotuberculosiksen bioserotyyppiä 2/O:3. Tämä serotyyppi on yleisin myös Suomessa. Belgialaisissa sioissa tätä serotyyppiä tavattiin 60%:ssa, englantilaisissa 34%:ssa ja italialaisissa 20%:ssa. Englannissa oli suurin biodiversiteetti eri serotyyppejä myös Y. pseudotuberculosiksen kohdalla. Samoista sioista tiloilta ja teurastamoilta eristetyt Y. enterocolitican ja Y. pseudotuberculosiksen identtiset genotyypit kertovat, että siat saavat Yersinia- kontaminaation jo tuottajatilalla ja Yersinia kulkeutuu sian mukana teurastamolle. Tutkimuksessa havaittiin, että suuri Y. enterocolitican esiintyvyys korreloi vesiautomaattityypin ja pehmikkeiden puuttumisen kanssa sekä tuhoeläinten pääsyn eston kanssa. Luomutiloilla tai alhaisen tuotantokapasiteetin omaavilla tuottajatiloilla havaittiin alhaisempi esiintyvyys kuin korkean tuotannon perinteisillä tuottajatiloilla. Y. pseudotuberculosiksen esiintyminen korreloi tuhoeläinten esiintymisen ja ulkoilmaolosuhteiden kanssa sekä sikojen lukumäärän kanssa. Luomutiloilla oli suurempi esiintyvyys Y. pseudotuberculosista kuin perinteisen tuotantomuodon omaavilla tuottajatiloilla