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Table 1 Categorical variables included in the bivariate analysis (chi-squared test with p < 0.2). Controls: 93 farms that remained brucellosis-free for at least three years. Cases: 98 herds previously free of brucellosis that became infected

From: Risk factors for new bovine brucellosis infections in Colombian herds

Variables Control Case OR 95% CI
Lower Upper p-value
Livestock type
 Dairya 68 (73.12%) 60 (61.22%) 1    
 Beef 8 (8.60%) 22 (22.45%) 3.12 1.29 7.52 0.009
 Dual purpose (beef and milk) 17 (18.28%) 16 (16.33%) 1.07 0.5 2.29 0.869
Equipment shared with other farms
 Noa 81 (87.10%) 77 (78.57%) 1    
 Yes 12 (12.90%) 21 (21.43%) 1.84 0.85 4 0.12
Cleaning and disinfection of clinical equipment and clothing
 Yesa 86 (92.47%) 85 (86.73%) 1    
 No 7 (7.53%) 13 (13.27%) 1.88 0.72 4.94 0.197
Presence of facilities to shelter animals
 Noa 41 (44.09%) 31 (31.63%) 1    
 Yes 52 (55.91%) 67 (68.37%) 1.7 0.94 3.08 0.077
Farm fencing
 Completelya 91 (97.85%) 91 (92.86%) 1    
 Partially 2 (2.15%) 7 (7.14%) 3.5 0.71 17.3 0.105
Contact of the herd with other neighbouring farms
 Noa 78 (83.87%) 67 (68.37%) 1    
 Yes 15 (16.13%) 31 (31.63%) 2.41 1.2 4.83 0.012
Infected animals in the neighbouring herd
 Noa 7 (7.53%) 2 (2.04%) 1    
 Yes 86 (92.47%) 96 (97.96%) 3.91 0.79 19.32 0.074
Mixed farm (farms that have species other than buffaloes or cattle)
 Noa 80 (86.02%) 72 (73.47%) 1    
 Yes 13 (13.98%) 26 (26.53%) 2.22 1.06 4.648 0.032
Water access points shared with other farms b
 No farms or brucellosis-free farmsa 59 (63.44%) 48 (48.98%) 1    
 Non-brucellosis-free farms 34 (36.56%) 50 (51.02%) 1.81 1.01 3.22 0.045
Presence of drainage from other farms
 Noa 58 (62.37%) 48 (48.98%) 1    
 Yes 35 (37.63%) 50 (51.02%) 1.73 0.97 3.07 0.063
Animal movement: Brucella status b of other herds at the destination
 Brucellosis-free farms or no movementa 89 (95.70%) 87 (88.78%) 1    
 Non-brucellosis-free farms 4 (4.30%) 11 (11.22%) 2.81 0.86 9.17 0.076
Status of the origin of replacement animalsb (internal or brucellosis-free farms vs calves from non-brucellosis-free farms)
 Brucellosis-free farms or internala 85 (91.40%) 67 (68.37%) 1    
 Non-brucellosis-free farms 8 (8.60%) 31 (31.63%) 4.92 2.12 11.39 < 0.001
Internal replacement with calves from the same farm whose mothers were positive
 Noa 89 (95.70%) 78 (79.59%) 1    
 Yes 4 (4.30%) 20 (20.41%) 5.71 1.87 17.41 0.001
Introduction of heifers < 24 months old into the farm
 No admittancea 79 (84.95%) 72 (73.47%) 1    
 Admittance 14 (15.05%) 26 (26.53%) 2.04 0.99 4.2 0.052
Number of cattle introduced into the farm (per year)
 Nonea 66 (70.97%) 53 (54.08%) 1    
 Ten or fewer 19 (20.43%) 23 (23.47%) 1.51 0.74 3.06 0.255
 Between eleven and thirty 6 (6.45%) 10 (10.20%) 2.08 0.71 6.08 0.178
 More than thirty 2 (2.15%) 12 (12.25%) 7.47 1.6 34.85 0.004
Infection status of the origin of the cattle b (of all ages)
 Tested negative for Brucella or brucellosis-free farma 71 (76.34%) 58 (59.18%) 1    
 Not tested, unknown status of the farm, positive herds 22 (23.66%) 40 (40.82%) 2.23 1.19 4.16 0.012
Introduction of other domestic species into the farm
 Nonea 88 (94.63%) 85 (86.74%) 1    
 More than twenty 0 (0.0%) 3 (3.06%) 7.25 0.37 142.37 0.13
 Less than or equal to twenty 5 (5.37%) 10 (10.20%) 2.07 0.68 6.31 0.194
Brucella status b of the origin of the bulls
 Artificial inseminationa 36 (38.71%) 34 (34.69%) 1    
 Free herds 44 (47.31%) 16 (16.33%) 0.39 0.18 0.81 0.011
 Unknown/positive status 13 (13.98%) 48 (48.98%) 3.91 1.81 8.46 < 0.001
Access of dogs and cats to/contact with aborted foetuses and reproductive discharges
 No (or no dogs)a 66 (70.97%) 59 (60.20%) 1    
 Yes 27 (29.03%) 39 (39.80%) 1.62 0.88 2.95 0.119
  1. aCategory considered as reference. Variables with more than two categories have been pairwise compared with this category
  2. bThe brucellosis status of other farms was obtained from the tests performed within the framework of the control programme