Skip to main content

Table 1 House-level categorical variables available for analysis of Campylobacter colonization of broilers in Iceland

From: House-level risk factors associated with the colonization of broiler flocks with Campylobacterspp. in Iceland, 2001 – 2004

Variables within subsets Description of variable or level Number of negative flocks Number of positive flocks
Ventilation    
Ventilation system – Regular cleaninga (n = 699) Yes (after each flock) 500 196
  Sometime (every other time on average) 2 1
Ventilation integrity (n = 758) Closed (wild birds or their faeces are unable to enter the house) 354 142
  Open (wild birds or their faeces are able to enter the house) 198 64
Ventilation typeb (n = 758) Both 153 80
  Horizontal 86 7
  Vertical 313 119
Roof and floor drainage    
Roof and floor drains mergec (n = 758) Roof drains are present & merge with floor drain 35 23
  Roof & floor drains do not merge or house does not have roof drains 517 183
Roof drain methodb (n = 758) House does not have roof drainsd 294 108
  Drains onto ground immediately outside the housed 129 45
  Drains into a ditch, trench, open area, field, or standing water near the housed 31 9
  Drains into water with a continuous flow 42 2
  Drains into a septic tank with overflow into an open trench 21 19
  Drains into a septic tank with overflow into an underground bed 35 23
Floor drains sealed (n = 758) Yes 468 198
  No 84 8
Floor drain method (n = 758) Drains onto ground immediately outside the housed 10 2
  Drains into a ditch, trench, open area, field, or standing water near the housed 28 12
  Drains into water with a continuous flow 117 45
  Drains into a septic tank with overflow into an open trench 108 61
  Drains into a septic tank with overflow into an underground bed 223 58
  Drains into sub-level of the house, then pumped out onto fieldsd 66 28
Building quality, materials and repair    
Heating of broiler house floorb (n = 699) Yes 172 106
  No 330 91
Quality of floor litter storage facility (n = 699) Very good (above specification or needs) 307 114
  Good or average (meets specification or needs)d 187 76
  Inferior (clearly below specification or needs)d 8 7
Floor – materiala (n = 699) Entirely concrete 496 194
  Includes wood elements 6 3
Floor – cracks fixed between flocksb (n = 699) Yes 231 100
  No 271 97
Wall material (within birds height) (n = 699) Metald 7 4
  Concreted 420 160
  Wood 75 33
Ceilingb (n = 699) Metal 341 154
  Concrete 57 8
  Wood 104 35
House water distribution system (n = 699) Nipples 378 150
  Other 124 47
House structure    
House shares a common wall with another house (n = 792) Yes 268 94
  No 307 123
Floor level (n = 792) Single-level house 546 199
  Multi-level house 29 18
House shares a common entrance with another house (n = 792) Yes 179 47
  No 396 170
Pest proofing    
Insect and rodent controlb (n = 699) Regular professional extermination 316 161
  Regular non-professional extermination 108 22
  No regular extermination 78 14
Construction pest proofing and sealing of house (n = 699) Very good 386 163
  Averaged 107 30
  Inferiord 9 4
Past evidence/observation of mice in house (n = 699) Very rarely (< 2 observations per year) 487 193
  Sometime (1 to 3 observations per month)d 9 1
  Often (1 or more observations per week)d 6 3
Vegetation within 1 m of house (n = 699) Yes 234 91
  No 268 106
Biosecurity    
Boots cleaned and disinfected before entry to houseb (n = 699) Always 325 164
  Sometime (according to need)d 13 1
  Neverd 164 32
Staff exclusively assigned to house (n = 699) Yes 174 72
  No 328 125
Boots changed before entry to housea (n = 699) Yes 499 196
  No 3 1
Split room entry to houseb (n = 699) Yes 284 145
  No 218 52
Sanitation    
Use of geothermal water for cleaningb (n = 699) Yes 336 175
  No 166 22
Use of chemical cleaner after clean-out and rinsee (n = 699) Yes 447 188
  No 55 9
Use of bacterial disinfectant and/or fumigatione (n = 699) Yes 463 193
  No 39 4
  1. a Variable excluded from the subset analysis due to the small number of observations (≤ 10) in one or more categories.
  2. b Variable retained after the subset analysis (p ≤ 0.15) for inclusion in the comprehensive model.
  3. c Variable excluded from the subset analysis due to high correlation (τ ≥ 0.8) with other variables (or categories of other variables) in the same subset.
  4. d Categories (denoted by d) of a variable were combined for the subset analysis due to the small number of observations (≤ 15) in one or more categories, and/or to group biologically meaningful categories together.
  5. e Variable excluded from the subset analysis due to the occurrence of cells with very low frequencies of observations when the variables were in the model together.