Porcine reproductive and respiratory syndrome virus (PRRSV) in GB pig herds: farm characteristics associated with heterogeneity in seroprevalence

Table 5 Model 3.

Variable	n	Coefficient	SE	p	CI^a		OR	CI^b
Intercept		2.85	0.16
Age category
8 weeks	24	reference
14 weeks	24	1.47	0.14	< 0.01	1.19	1.75	23.57	11.32	49.06
Gilts	25	1.52	0.15	< 0.01	1.23	1.81	26.31	11.99	57.74
Parity 1	25	1.36	0.15	< 0.01	1.07	1.65	13.37	6.14	29.11
Parity 2	25	1.52	0.15	< 0.01	1.22	1.81	22.81	10.39	50.05
Parity 3	24	1.6	0.15	< 0.01	1.3	1.9	29.93	13.32	67.25
Parity 4	24	1.38	0.15	< 0.01	1.09	1.68	17.98	8.21	39.37
Parity 5+	24	1.42	0.15	< 0.01	1.13	1.71	14.73	6.75	32.14
Purchased gilts
No	13
Yes	12	-0.61	0.16	< 0.01	-0.92	-0.29	0.35	0.18	0.7
Length of time purchased stock isolated
Not isolated	14	reference
1–5 days	3	-0.36	0.25	0.14	-0.85	0.12	0.61	0.21	1.77
6 days or more	8	-0.46	0.18	< 0.01	-0.81	-0.11	0.43	0.2	0.93
Pig free time for visitors
< 48 hours	17	reference
≥ 48 hours	8	-0.44	0.18	< 0.05	-0.79	-0.1	0.44	0.2	0.93
Estimation of random effects:
Variation between herds		0.11	0.04
Variation between pens		0.2	0.03
Variation between pigs		0.45	0.02

Multivariable three level mixed model of factors associated with log IRPC of 1184 pigs belonging to 25 herds that had seropositive young stock.
Sample size (n); standard error (SE); probability function (p); 95% confidence interval (CI^a) when pigs' log IRPC (+12) values were used as a continuous outcome variable; Odds Ratios (OR) and 95% confidence interval (CI^b) when pig-level seropositivity (absence/presence of antibodies) was used as a comparative binary outcome variable (exp(coefficient+/-(1.96 × standard error))).

ISSN: 1746-6148