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Doctoral thesis, 2011

Wild rodents as carriers of potential pathogens to pigs, chickens and humans

Backhans, Annette


The aim of this thesis was to investigate the specific risks that rodents constitute for proliferation of pathogens and transmission of those to farm animals, and indirectly to humans. Rodents were captured in pig and chicken flocks, in wastewater treatment plants and other urban environments. The enteric pig pathogens Brachyspira hyodysenteriae and B. pilosicoli and the chicken pathogen B. intermedia were detected. Fingerprinting by Random Amplified Polymorphic DNA and Pulsed Field Gel Electrophoresis indicated cross-species transmission of B. pilosicoli, B. intermedia, B. innocens, and B. murdochii between rodents and farm animals. A phylogeny of murine brachyspiras was established. Three new genetic rodent variants of Brachyspira spp. were discovered, for which the provisional names ‘B. rattus’, ‘B. muridarum’ and ‘B. muris’ were suggested. Lawsonia intracellularis and encephalomyocarditis virus (EMCV) were detected in rodents trapped on pig farms. The clinical significance of leptospirosis in Sweden is reportedly minor. However, the detection of pathogenic leptospiras in mice, rats and a water vole indicated that rodents constitute a potential hazard to pigs and humans. Campylobacteriosis, salmonellosis and yersiniosis are the most frequently reported zoonosis in Europe. Rodents in the study carried C. jejuni, C. coli and C. upsaliensis. Identical isolates of the human pathogen Yersinia enterocolitica bioserotype 4/O:3 were isolated both from rodents and pigs on the same farm, indicating cross-species transmission. Salmonella enterica could not be detected by the applied real-time PCR, indicating a low sensitivity of this test. No zoonotic variants of Giardia spp. or Cryptosporidium spp. were detected. All samples were tested negative for Trichinella spp. indicating that trichinellosis is not a widespread infection in wild rodents in Sweden. No rodents were seropositive to Toxoplasma gondii. In conclusion, the results show that rodents could be a risk for the transmission of the pig pathogens Lawsonia intracellularis, Brachyspira hyodysenteriae, B. pilosicoli, pathogenic Leptospira spp. and EMCV, and zoonotic Campylobacter species and Yersinia enterocolitica 4/O:3 in Sweden.


swine; chickens; rodents; pathogens; disease transmission; sweden

Published in

Acta Universitatis Agriculturae Sueciae
2011, number: 44
ISBN: 978-91-576-7588-0
Publisher: Department of Clinical Sciences, Swedish University of Agricultural Sciences

Authors' information

Swedish University of Agricultural Sciences, Department of Clinical Sciences

UKÄ Subject classification

Clinical Science

URI (permanent link to this page)