title: House Sparrows Do Not Constitute a Significant Salmonella Typhimurium Reservoir across Urban Gradients in Flanders, Belgium.
abstract: In recent decades major declines in urban house sparrow (Passer domesticus) populations have been observed in north-western European cities, whereas suburban and rural house sparrow populations have remained relatively stable or are recovering from previous declines. Differential exposure to avian pathogens known to cause epidemics in house sparrows may in part explain this spatial pattern of declines. Here we investigate the potential effect of urbanization on the development of a bacterial pathogen reservoir in free-ranging house sparrows. This was achieved by comparing the prevalence of Salmonella enterica subspecies enterica serotype Typhimurium in 364 apparently healthy house sparrows captured in urban, suburban and rural regions across Flanders, Belgium between September 2013 and March 2014. In addition 12 dead birds, received from bird rescue centers, were necropsied. The apparent absence of Salmonella Typhimurium in fecal samples of healthy birds, and the identification of only one house sparrow seropositive for Salmonella spp., suggests that during the winter of 2013-2014 these birds did not represent any considerable Salmonella Typhimurium reservoir in Belgium and thus may be considered naïve hosts, susceptible to clinical infection. This susceptibility is demonstrated by the isolation of two different Salmonella Typhimurium strains from two of the deceased house sparrows: one DT99, typically associated with disease in pigeons, and one DT195, previously associated with a passerine decline. The apparent absence (prevalence: <1.3%) of a reservoir in healthy house sparrows and the association of infection with clinical disease suggests that the impact of Salmonella Typhimurium on house sparrows is largely driven by the risk of exogenous exposure to pathogenic Salmonella Typhimurium strains. However, no inference could be made on a causal relationship between Salmonella infection and the observed house sparrow population declines.
authors.affiliation: Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Lieze Oscar
authors.initials: LO
authors.lastname: Rouffaer
authors.affiliation: Department of Biology, Terrestrial Ecology Unit, Ghent University, Ghent, Belgium.
authors.forename: Luc
authors.initials: L
authors.lastname: Lens
authors.affiliation: Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Roel
authors.initials: R
authors.lastname: Haesendonck
authors.affiliation: Department of Biology, Terrestrial Ecology Unit, Ghent University, Ghent, Belgium.
authors.forename: Aimeric
authors.initials: A
authors.lastname: Teyssier
authors.affiliation: Department of Biology, Terrestrial Ecology Unit, Ghent University, Ghent, Belgium.|Department of Biological Sciences, Faculty of Science & Mathematics, Universiti Pendidikan Sultan Idris, Perak, Malaysia.
authors.forename: Noraine Salleh
authors.initials: NS
authors.lastname: Hudin
authors.affiliation: Department of Biology, Terrestrial Ecology Unit, Ghent University, Ghent, Belgium.
authors.forename: Diederik
authors.initials: D
authors.lastname: Strubbe
authors.affiliation: Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Freddy
authors.initials: F
authors.lastname: Haesebrouck
authors.affiliation: Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Frank
authors.initials: F
authors.lastname: Pasmans
authors.affiliation: Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: An
authors.initials: A
authors.lastname: Martel
mesh_terms: D000818:Animals; D001530:Belgium / Q000453:epidemiology; D001715:Bird Diseases / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission; D002947:Cities; D004197:Disease Reservoirs / Q000382:microbiology; D005260:Female; D008297:Male; D011157:Population Dynamics; D012481:Salmonella Infections, Animal / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission; D012486:Salmonella typhimurium / Q000472:pathogenicity* / Q000502:physiology; D012621:Seasons; D046370:Sparrows / Q000382:microbiology*; D014507:Urbanization