Table 4. The odds ratio for infection with A. marginale, at 95% confidence intervals (CI).

Risk factor Level Odds ratio 95% CI P value AEZ Grazing system       Lowland Fenced 1.13 .41–3.18 0.05 Lowland Free range 3.74 1.75–8.16**   Lowland Tethered 3.18 .93–12.18   Lowland Zero grazing 0.63 .18–2.05   Midland and upland Fenced 0.31 .11–.84*   Midland and upland Free range 0.71 .21–2.36   Midland Tethered 0.84 .30–2.25   Midland Zero grazing 0.3 .12–.74*   Upland Tethered 1.13 .51–2.59   Upland Zero grazing 1 –   Age group (months)         0–3   0.29 .15–.54* 0.05 4–12   0.41 .25–.66*   13–18   0.96 .37–2.46   >18   1 –

* Low risk of infection ** High risk of infection