title: Occurrence of Salmonella spp.: a comparison between indoor and outdoor housing of broilers and laying hens.
abstract: BACKGROUND
  Outdoor production of poultry is rapidly increasing, which could be associated with increased risks for exposure to different environmental sources of Salmonella. We report a comparison on the occurrence of Salmonella during 2007-2015 in broilers and laying hens in outdoor and indoor production subjected to the same requirements for the prevention and control of Salmonella as applied in Sweden.
  
  
  RESULTS
  Our results give no indication that, during the period studied, the exposure to Salmonella in outdoor poultry production was higher than in the indoor production. The annual incidence of Salmonella infected flocks in outdoor production remained at a very low and at a similar level as for indoor production. For laying hens the annual proportion of birds in test positive flocks ranged from 0 to 1.3% for indoor production from 0 to 2.0% for outdoor production. For broilers the proportion of Salmonella infected flocks (2013-2015) was 0.16% for indoor, and 0% in outdoor production. The difference was not statistically significant and was further reduced when flocks infected due to vertical transmission or from a hatchery source were excluded. It should, however, be considered that the number of outdoor flocks included in this evaluation is very small and continuous evaluation is needed.
  
  
  CONCLUSIONS
  New animal production systems, including those driven by consumer and welfare demands, may be associated with a higher risk for the exposure of potential pathogens to food animals and possibly also subsequent outbreaks of food borne infections. In this study no increase in the risk for exposure of flocks to Salmonella in outdoor poultry production was found. The situation may well change and the possibility of Salmonella contamination in outdoor poultry production requires continuous attention.
authors.affiliation: Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, P.O. Box 7028, SE-75007, Uppsala, Sweden. martin.wierup@slu.se.
authors.forename: Martin
authors.identifier: http://orcid.org/0000-0001-9075-3839
authors.initials: M
authors.lastname: Wierup
authors.affiliation: Department of Disease Control and Epidemiology, National Veterinary Institute, SVA, SE-751 89, Uppsala, Sweden.
authors.forename: Helene
authors.initials: H
authors.lastname: Wahlström
authors.affiliation: Department of Disease Control and Epidemiology, National Veterinary Institute, SVA, SE-751 89, Uppsala, Sweden.
authors.forename: Elina
authors.initials: E
authors.lastname: Lahti
authors.affiliation: Department of Animal Health and Antimicrobial Strategies, National Veterinary Institute, SVA, Österåkersvägen 21, SE-81040, Hedesunda, Sweden.
authors.forename: Helena
authors.initials: H
authors.lastname: Eriksson
authors.affiliation: Department of Animal Health and Antimicrobial Strategies, National Veterinary Institute, SVA, Österåkersvägen 21, SE-81040, Hedesunda, Sweden.
authors.forename: Désirée S
authors.initials: DS
authors.lastname: Jansson
authors.affiliation: Åsa Odelros AB, Österåkersvägen 21, SE-81040, Hedesunda, Sweden.
authors.forename: Åsa
authors.initials: Å
authors.lastname: Odelros
authors.affiliation: Department of Disease Control and Epidemiology, National Veterinary Institute, SVA, SE-751 89, Uppsala, Sweden.
authors.forename: Linda
authors.initials: L
authors.lastname: Ernholm
mesh_terms: D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D002645:Chickens; D005260:Female; D006799:Housing, Animal; D015994:Incidence; D008297:Male; D011201:Poultry Diseases / Q000453:epidemiology*; D012307:Risk Factors; D012475:Salmonella / Q000302:isolation & purification; D012481:Salmonella Infections, Animal / Q000453:epidemiology*; D013548:Sweden / Q000453:epidemiology
keywords: Broiler; Environmental exposure; Free-range; Indoor poultry production; Laying hen; Outdoor poultry production; Salmonella; Wildlife