title: Experimental Infection of voles with Francisella tularensis indicates their amplification role in tularemia outbreaks.
abstract: Tularemia outbreaks in humans have been linked to fluctuations in rodent population density, but the mode of bacterial maintenance in nature is unclear. Here we report on an experiment to investigate the pathogenesis of Francisella tularensis infection in wild rodents, and thereby assess their potential to spread the bacterium. We infected 20 field voles (Microtus agrestis) and 12 bank voles (Myodes glareolus) with a strain of F. tularensis ssp. holarctica isolated from a human patient. Upon euthanasia or death, voles were necropsied and specimens collected for histological assessment and identification of bacteria by immunohistology and PCR. Bacterial excretion and a rapid lethal clinical course with pathological changes consistent with bacteremia and tissue necrosis were observed in infected animals. The results support a role for voles as an amplification host of F. tularensis, as excreta and, in particular, carcasses with high bacterial burden could serve as a source for environmental contamination.
authors.affiliation: Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
authors.forename: Heidi
authors.initials: H
authors.lastname: Rossow
authors.affiliation: Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland; Finnish Forest Research Institute, Vantaa, Finland.
authors.forename: Kristian M
authors.initials: KM
authors.lastname: Forbes
authors.affiliation: Division of Clinical Microbiology, Helsinki University Hospital Laboratory (HUSLAB), Helsinki, Finland.
authors.forename: Eveliina
authors.initials: E
authors.lastname: Tarkka
authors.affiliation: Centre for Biothreat Preparedness, Centre for Military Medicine, Finnish Defence Forces, Helsinki, Finland.
authors.forename: Paula M
authors.initials: PM
authors.lastname: Kinnunen
authors.affiliation: Centre for Biothreat Preparedness, Centre for Military Medicine, Finnish Defence Forces, Helsinki, Finland.
authors.forename: Heidi
authors.initials: H
authors.lastname: Hemmilä
authors.affiliation: Finnish Forest Research Institute, Vantaa, Finland.
authors.forename: Otso
authors.initials: O
authors.lastname: Huitu
authors.affiliation: Centre for Biothreat Preparedness, Centre for Military Medicine, Finnish Defence Forces, Helsinki, Finland.
authors.forename: Simo
authors.initials: S
authors.lastname: Nikkari
authors.affiliation: Finnish Forest Research Institute, Vantaa, Finland.
authors.forename: Heikki
authors.initials: H
authors.lastname: Henttonen
authors.affiliation: Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland; Finnish Centre for Laboratory Animal Pathology, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland; School of Veterinary Science and Department of Infection Biology, Institute of Global Health, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Anja
authors.initials: A
authors.lastname: Kipar
authors.affiliation: Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland; Division of Clinical Microbiology, Helsinki University Hospital Laboratory (HUSLAB), Helsinki, Finland; Department of Virology, Haartman Institute, University of Helsinki, Helsinki, Finland.
authors.forename: Olli
authors.initials: O
authors.lastname: Vapalahti
mesh_terms: D000818:Animals; D003411:Arvicolinae / Q000382:microbiology*; D004196:Disease Outbreaks; D005604:Francisella tularensis / Q000302:isolation & purification*; D014406:Tularemia / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission*