Table 5. Most relevant farm characteristics associated to MRSA in veal calves obtained from the multiple regression models during the study period in the 51 farms, the Netherlands 2010–2012.
1st production cycle: ORs for a pooled sample to be MRSA-positive | 2nd production cycle: ORs for an individual animal sample to be MRSA-positive | ||||||||
---|---|---|---|---|---|---|---|---|---|
Variable a | Category | N b | OR | 95% CI | P-value c | N b | OR | 95% CI | P-value c |
Sampling time | Week 0 | 510 | 0.20 | 0.15–0.28 | <0.01 | 1408 | 0.09 | 0.07–0.12 | <0.01 |
Week 12 | 510 | Ref. | - | - | 1404 | Ref. | - | - | |
Origin of veal calves d | Just from the Netherlands | 160 | 2.36 | 0.78–7.11 | 0.13 | 361 | 3.63 | 0.93–14.20 | 0.06 |
The Netherlands or neighbor country | 640 | 3.11 | 1.33–7.23 | 0.01 | 1738 | 7.07 | 2.58–19.40 | <0.01 | |
Not neighbor country | 220 | Ref | - | - | 713 | Ref. | - | - | |
Number of stables | 4 to 6 | 100 | 3.18 | 1.09–9.22 | 0.03 | NA | NA | NA | NA |
1 to 3 | 920 | Ref. | - | - | NA | NA | NA | NA | |
Ventilation of stables | Mechanical | NA | NA | NA | NA | 2023 | 0.23 | 0.10–0.53 | <0.01 |
Natural | NA | NA | NA | NA | 789 | Ref. | - | - | |
Presence of free-ranging cats in the farm | Yes | 540 | 2.14 | 1.11–4.12 | 0.02 | 1495 | 2.25 | 1.01–5.02 | 0.05 |
No | 480 | Ref | - | - | 1317 | Ref. | - | - |
Multiple regression associations after backward elimination from 2 full models containing variables with p<0.2 in the univariate analysis (Table 4) for each of the production cycles. P-values <0.05 are in boldface. MRSA, methicillin resistant Staphylococcus aureus; Ref., reference category of the variable; NA, variable not retained in the final model.
a Presented variables comply with the following criteria in at least one study cycle: i) less than 10% missing observations; ii) more than 10% of observations in each of the categories of a variable; iii) p ≤ 0.10.
b Maximum number of observations: i) in first cycle n = 1020 pools (10 pools in 51 farms in 2 sampling moments); ii) in the second cycle n = 2812 animals (mean of 28 animals sampled per farm in 51 farms in 2 sampling moments).
c Wald p-value.
d Neighboring countries from which animals are imported: Luxemburg (8 farms), Belgium (11 farms) and Germany (29 farms). Not neighboring countries were mostly Poland (16 farms), Latvia (5 farms) and Lithuania (13 farms). Overall p = 0.03 in first cycle and p<0.01 in second cycle.