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Table 1 Description of flock data variables tested in univariable screening (Chi2-test)

From: Flock-level risk factors for outbreaks of infectious arthritis in lambs, Norway 2018

Variable Categories Total Case flocks (n = 84) Control flocks (n = 1414)
n % n % n % P-value
Number of lambs (ear-tagged, categorized)a < 200 1014 67.7 36 42.9 978 69.2 < 0.0001
200–500 427 28.5 36 42.9 391 27.7  
> 500 57 3.8 12 14.3 45 3.2  
Outbreak of infectious arthritis before 2018c No 1286 85.9 18 21.4 1268 89.7 < 0.0001
Yes 212 14.2 66 78.6 146 10.3  
Lambing percentageb ≤ 200 592 39.7 19 22.6 573 39.7 0.001
> 200 898 60.3 65 77.4 833 60.3  
Breedb Breed other than Norwegian White Sheep 301 20.5 7 8.9 294 21.1 0.009
Norwegian White Sheep 1171 79.6 72 91.1 1099 78.9  
Start of lambing seasonb April 1181 79.2 62 73.8 1119 73.8 0.038
May 189 12.7 9 10.7 180 12.7  
March 121 8.1 13 15.5 108 7.7  
Length of lambing seasonb < 4 weeks 921 61.5 44 52.4 877 62.1 0.076
> 4 weeks 576 38.5 40 47.6 536 37.9  
  1. aNot tested in the multivariable model due to collinearity with number of ear-tagged lambs (continuous, not shown)
  2. bTested in multivariable model
  3. cIntervening variable, not tested in the multivariable model
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Acta Veterinaria Scandinavica

ISSN: 1751-0147

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