Spread of porcine circovirus associated disease (PCVAD) in Ontario (Canada) swine herds: Part II. Matched case-control study

Poljak, Zvonimir; Dewey, Catherine E; Rosendal, Thomas; Friendship, Robert M; Young, Beth; Berke, Olaf

doi:10.1186/1746-6148-6-58

Table 2 Univariable associations for variables considered for multivariable analysis, including interaction between high-risk local exposure and time of matching

From: Spread of porcine circovirus associated disease (PCVAD) in Ontario (Canada) swine herds: Part II. Matched case-control study

Variable	Odds ratio	95% CI	P ^a	Overall P^b
Estimates based on the maximum likelihood method using assumption of Gaussian distribution
Herd PRRSv-positive status (no = ref^c)	1.56	(0.89, 2.75)	0.121	0.107
Herd type				0.090
Farrow-to-finish	- -	-	-
Farrow-to-grow	1.23	(0.70, 2.18)	0.473
Finisher	1.47	(0.96, 2.26)	0.077
Nursery	0.74	(0.43, 1.27)	0.275
Nursery and finisher	0.59	(0.23, 1.51)	0.274
Easting (100 kms)				0.002
linear	1.54	(1.17, 2.03)	0.002
Cumulative local exposure (CLE) (no = ref)	1.05	(0.64, 1.70)	0.852	0.852
High-risk local exposure(HRLE) (no = ref)	2.26	(1.06, 4.83)	0.035	0.040
HRLE*Time interaction model				0.005
HRLE	0.04	(0.00, 1.74)	0.094	-
HRLE*Time (Month)	1.21	(1.02, 1.44)	0.031	0.0128
Local # of high-risk herds LNHRH (continuous)	2.16	(1.06, 4.39)	0.033	0.036
Local # of high-risk herds LNHRH (nominal; 0 = ref)				0.111
One	2.20	(1.02, 4.76)	0.045
Two	4.03	(0.24, 67.50)	0.333
Ownership-adjusted high-risk local exposure (OWHRLE; No high-risk local exposure = ref)				0.001
High-risk local exposure within ownership	1.0E+7	(not estimated)	0.984
High-risk local exposure outside of ownership	1.31	(0.54, 3.17)	0.555
Number of direct contacts^d/month	0.95	(0.88, 1.03)	0.221	0.205
Number of indirect contacts/month	1.02	(0.98, 1.07)	0.256	0.263
Number of nursery contacts/month	0.93	(0.85, 1.02)	0.106	0.086
Number of breeding contacts/month^e	1.03	(0.96, 1.10)	0.407	0.407
Number of feed contacts/month	1.06	(1.00, 1.12)	0.043	0.045
Estimates of the high-risk local exposure obtained using exact logistic regression
Herd PRRSv-positive status (no = ref)	1.56	(0.87, 2.95)	0.151	0.151
Cumulative local exposure (CLE) (no = ref)	1.05	(0.62, 1.74)	0.901	0.901
High-risk local exposure(HRLE) (no = ref)	2.26	(0.97, 5.18)	0.049	0.049
Local # of high-risk herds LNHRH (continuous)	2.16	(0.99, 4.69)	0.043	0.043
Local # of high-risk herds LNHRH (nominal; 0 = ref)				0.108
One	2.18	(0.92, 5.04)	0.049
Two	4.03	(0.05, 330.32)	0.367
Ownership-adjusted high-risk local exposure (OWHRLE; No high-risk local exposure = ref)				0.001
High-risk local exposure within ownership	20.17^f	(2.75, +inf)	0.001
High-risk local exposure outside of ownership	1.31	(0.46, 3.39)	0.634

^a Based on the Wald test for conditional maximum likelihood.
^b Based on the Likelihood ratio test for conditional maximum likelihood.
^c ref = referent group.
^d Frequency of all contacts was calculated on the basis of visits to herds.
^e Based on 230 observations where such information was applicable.
^f Median unbiased estimator.

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ISSN: 1746-6148

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