title: House-level risk factors associated with the colonization of broiler flocks with Campylobacter spp. in Iceland, 2001 - 2004.
abstract: BACKGROUND
  The concurrent rise in consumption of fresh chicken meat and human campylobacteriosis in the late 1990's in Iceland led to a longitudinal study of the poultry industry to identify the means to decrease the frequency of broiler flock colonization with Campylobacter. Because horizontal transmission from the environment is thought to be the most likely source of Campylobacter to broilers, we aimed to identify broiler house characteristics and management practices associated with flock colonization. Between May 2001 and September 2004, pooled caecal samples were obtained from 1,425 flocks at slaughter and cultured for Campylobacter. Due to the strong seasonal variation in flock prevalence, analyses were restricted to a subset of 792 flocks raised during the four summer seasons. Logistic regression models with a farm random effect were used to analyse the association between flock Campylobacter status and house-level risk factors. A two-stage process was carried out. Variables were initially screened within major subsets: ventilation; roof and floor drainage; building quality, materials and repair; house structure; pest proofing; biosecurity; sanitation; and house size. Variables with p < or = 0.15 were then offered to a comprehensive model. Multivariable analyses were used in both the screening stage (i.e. within each subset) and in the comprehensive model.
  
  
  RESULTS
  217 out of 792 flocks (27.4%) tested positive. Four significant risk factors were identified. Campylobacter colonization was predicted to increase when the flock was raised in a house with vertical (OR = 2.7), or vertical and horizontal (OR = 3.2) ventilation shafts, when the producer's boots were cleaned and disinfected prior to entering the broiler house (OR = 2.2), and when the house was cleaned with geothermal water (OR = 3.3).
  
  
  CONCLUSIONS
  The increased risk associated with vertical ventilation shafts might be related to the height of the vents and the potential for vectors such as flies to gain access to the house, or, increased difficulty in accessing the vents for proper cleaning and disinfection. For newly constructed houses, horizontal ventilation systems could be considered. Boot dipping procedures should be examined on farms experiencing a high prevalence of Campylobacter. Although it remains unclear how geothermal water increases risk, further research is warranted to determine if it is a surrogate for environmental pressures or the microclimate of the farm and surrounding region.
authors.affiliation: Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, Ontario, N1G 2W1, Canada. mguerin@uoguelph.ca
authors.forename: Michele T
authors.initials: MT
authors.lastname: Guerin
authors.forename: Wayne
authors.initials: W
authors.lastname: Martin
authors.forename: Jarle
authors.initials: J
authors.lastname: Reiersen
authors.forename: Olaf
authors.initials: O
authors.lastname: Berke
authors.forename: Scott A
authors.initials: SA
authors.lastname: McEwen
authors.forename: Jean-Robert
authors.initials: JR
authors.lastname: Bisaillon
authors.forename: Ruff
authors.initials: R
authors.lastname: Lowman
mesh_terms: D000818:Animals; D002167:Campylobacter / Q000254:growth & development*; D002169:Campylobacter Infections / Q000453:epidemiology / Q000382:microbiology / Q000635:transmission / Q000662:veterinary*; D002645:Chickens; D006799:Housing, Animal; D007055:Iceland / Q000453:epidemiology; D007410:Intestinal Diseases / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D008137:Longitudinal Studies; D015999:Multivariate Analysis; D011201:Poultry Diseases / Q000453:epidemiology / Q000382:microbiology* / Q000635:transmission; D012307:Risk Factors; D012621:Seasons; D011795:Surveys and Questionnaires