Table 2 Unconditional associations between categorical independent variables and infection status of 41 study herds in Ireland during November 2007

Herd size

1) 4-32 animals

27

18

30

2) 33-55 animals

24

45

17

3) 56-88 animals

24

27

23

0.2256

4) 89-320 animals

24

9

30

Number of farm-bought cattle during 2007

1) 0 animals

37

45

33

2) 1-2 animals

22

18

23

3) 3-5 animals

22

9

27

0.6000

4) 6-22 animals

20

27

17

Closed herd '07

Yes

20

27

17

No

80

73

83

0.6582

Percentage purebred

1) 0-50%

37

27

40

2) 51-90%

29

27

30

0.6795

3) 91-100%

34

45

30

Average herd age

1) 1.77-3.01 years

27

27

27

2) 3.02-3.40 years

24

18

27

3) 3.41-3.75 years

24

45

17

0.2612

4) 3.76-4.98 years

24

9

30

Percentage homebred

1) 15-79%

63

45

70

0.2720

2) 80-100%

37

55

30