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

Guerin, Michele T; Martin, Wayne; Reiersen, Jarle; Berke, Olaf; McEwen, Scott A; Bisaillon, Jean-Robert; Lowman, Ruff

doi:10.1186/1746-6148-3-30

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 cleaning^a (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 type^b (n = 758)	Both	153	80
	Horizontal	86	7
	Vertical	313	119
Roof and floor drainage
Roof and floor drains merge^c (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 method^b (n = 758)	House does not have roof drains^d	294	108
	Drains onto ground immediately outside the house^d	129	45
	Drains into a ditch, trench, open area, field, or standing water near the house^d	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 house^d	10	2
	Drains into a ditch, trench, open area, field, or standing water near the house^d	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 fields^d	66	28
Building quality, materials and repair
Heating of broiler house floor^b (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 – material^a (n = 699)	Entirely concrete	496	194
	Includes wood elements	6	3
Floor – cracks fixed between flocks^b (n = 699)	Yes	231	100
	No	271	97
Wall material (within birds height) (n = 699)	Metal^d	7	4
	Concrete^d	420	160
	Wood	75	33
Ceiling^b (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 control^b (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
	Average^d	107	30
	Inferior^d	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 house^b (n = 699)	Always	325	164
	Sometime (according to need)^d	13	1
	Never^d	164	32
Staff exclusively assigned to house (n = 699)	Yes	174	72
	No	328	125
Boots changed before entry to house^a (n = 699)	Yes	499	196
	No	3	1
Split room entry to house^b (n = 699)	Yes	284	145
	No	218	52
Sanitation
Use of geothermal water for cleaning^b (n = 699)	Yes	336	175
	No	166	22
Use of chemical cleaner after clean-out and rinse^e (n = 699)	Yes	447	188
	No	55	9
Use of bacterial disinfectant and/or fumigation^e (n = 699)	Yes	463	193
	No	39	4

^a Variable excluded from the subset analysis due to the small number of observations (≤ 10) in one or more categories.
^b Variable retained after the subset analysis (p ≤ 0.15) for inclusion in the comprehensive model.
^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.
^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.
^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.

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ISSN: 1746-6148

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