Flock-level risk factors for outbreaks of infectious arthritis in lambs, Norway 2018

Table 2 Description of variables for housing conditions tested in the univariable screening (Chi²-test)

Variable	Categories	Total		Case flocks (n = 84)		Control flocks (n = 1414)
Variable	Categories	n	%	n	%	n	%	P-value
Flooring type in lambing pen^a	Metal mesh flooring	649	43.4	26	31.0	623	44.1	< 0.0001
	Plastic mesh flooring	314	21.0	41	48.8	273	19.3
	Other/combinations	533	35.6	17	20.2	516	36.6
Flooring type for lambs before let out onto pasture^b	Metal mesh flooring	348	23.2	21	25.3	327	23.2	< 0.0001
	Plastic mesh flooring	145	9.7	26	31.3	119	8.4
	Straw bed/deep litter	310	20.8	10	12.1	300	21.3
	Other/combinations	691	46.3	26	31.3	665	47.1
Bedding material in single pens^c	Not using bedding material	355	23.4	20	24.1	335	23.8	0.005
	Straw	493	33.1	42	50.6	451	32.0
	Sawdust	178	12.0	9	10.8	169	12.0
	Hay	167	11.2	6	7.2	161	11.4
	Other bedding materials or combinations	271	18.2	6	7.2	265	18.8
	Not using single pens	27	1.8	0	0	27	1.9
Age of the shed^a	> 10 years	952	63.9	41	48.8	911	64.8	0.01
	Rebuilt/modernized the last 10 years	282	18.9	21	25.0	261	18.6
	< 10 years	256	17.2	22	26.2	234	16.6
Environment in the shed after lambing vs. before^a	Dry	611	42.4	26	31.0	585	43.1	0.021
	More humid	426	29.6	24	28.6	402	29.7
	More humid and dirtier	403	28.0	34	40.5	369	27.2
Time spent in single pens after lambing^c	≥ 3 days	840	56.2	38	45.2	802	56.8	0.031
	1–2 days	628	42.0	46	54.8	582	41.3
	Not using single pens	27	1.8	0	0.0	27	1.9
Group size (ewes before lambing)^a	≤ 15	767	53.0	36	42.9	731	53.7	0.086
	16–30	441	30.5	28	33.3	413	30.3
	> 30	238	16.5	20	23.8	218	16.0
Housing type	Uninsulated	405	27.3	19	22.6	386	27.6	0.512
	Insulated	745	50.2	47	56.0	698	49.9
	Other housing type, outdoors combination	333	22.5	18	21.4	315	22.5

^aTested in multivariable model
^bIntervening variable, not tested in the multivariable model
^cNot tested in the multivariable model due to categories with five or fewer observations

ISSN: 1751-0147