Calves shedding Mycobacterium avium subspecies paratuberculosis are common on infected dairy farms

Table 3 Predictors for Mycobacterium avium subsp. paratuberculosis environmental sample culture results ( n = 139)

	n (% pos) ¹	Odds/OR	95% CI	P -value
Intercept		0.01	0.00 – 0.16	<0.01
Age group				0.39
<3 months	31 (3)	Reference
3 – 6 months	39 (13)	4.67	0.46 – 47.65	0.19
6 months – 1 year	25 (24)	10.52	1.01 - 116.87	0.05
1 – 2 years	38 (18)	7.56	0.74 – 76.91	0.09
>2 years	6 (17)	9.57	0.38 – 240.56	0.17
IS900 within-pen prevalence²				0.92
0	75 (12)	Reference
0.01 – 0.19	42 (17)	0.94	0.27 – 3.26	0.93
>0.2	22 (18)	1.32	0.25 – 6.93	0.74
Random effects		Var. (SE)		% Var.
Herd		0.70 (0.89)		17
Pen		-		83

Descriptive statistics and final multilevel logistic regression model.
¹Sample size (% culture-positive samples).
²Parameter included in the model because of evidence for an association in the descriptive statistics and biological plausibility.

ISSN: 1297-9716