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Table 7 Comparisons of identification of D. nodosus by the aprV2 rtPCR and culture/gelatinase gel test from subsets of presence/absence or both of foot lesions from the clinically affected flocks, consisting of 135 clinically affected sheep and 35 clinically healthy sheep

From: Assessment of a rtPCR for the detection of virulent and benign Dichelobacter nodosus, the causative agent of ovine footrot, in Australia

Flocks

Sheep clinical status (foot lesions)

No. sheep tested

aprV2 PCR Run/Cut-off

Culture Gelatinase Thermostable (Virulent) vs aprV2 PCR

Percentage positive results

Concordant results

Culture +ve

PCR + ve

p value

Kappa

Culture

aprV2 PCR

+ve

-ve

PCR -ve

Culture -ve

12 to 24

+ve

135

Run 1 / 40

31

17

0

87

< 0.0001

0.082

23.0%

87.4%

12 to 24

+ve

135

Run 1 / 35

31

20

0

84

< 0.0001

0.1

23.0%

85.2%

12 to 14

-ve

35

Run 1 / 40

3

16

0

16

0.0002

0.146

8.6%

54.3%

12 to 14

-ve

35

Run 2 / 40

3

12

0

20

< 0.0001

0.093

8.6%

65.7%

12 to 14

-ve

35

Run 1 / 35

3

20

0

12

0.0015

0.222

8.6%

42.9%

12 to 14

-ve

35

Run 2 / 35

3

19

0

13

0.0009

0.2

8.6%

45.7%

12 to 14

-ve & + ve

72

Run 1 / 40

9

20

0

43

< 0.0001

0.104

12.50%

72.20%

12 to 14

-ve & + ve

72

Run 2 / 40

9

16

0

47

< 0.0001

0.078

12.50%

77.80%

12 to 14

-ve & + ve

72

Run 1 / 35

9

27

0

36

< 0.0001

0.158

12.50%

62.50%

12 to 14

-ve & + ve

72

Run 2 / 35

9

27

0

36

< 0.0001

0.158

12.50%

62.50%

12 to 24

-ve & + ve

170

Run 1 / 40

34

33

0

103

< 0.0001

0.114

20.0%

80.6%

12 to 24

-ve & + ve

170

Run 1 / 35

34

40

0

96

< 0.0001

0.143

20.0%

76.5%

  1. The p-value for McNemar’s test for independence between culture gelatinase thermostable (Virulent) and aprV2 PCR result is shown. Detection rates of both culture and rtPCR are presented as percentage positive results