Table 1.
Characteristics of farm, sample and environmental variables stratified by C. spp. status from 20 small-scale diversified California farms sampled between May 2015 and June 2016
| Variable | Negative for C. spp N = 900 | Positive for C. spp. N = 109 | P-value | # of analysed samples |
|---|---|---|---|---|
| Years farming | 0.001 | 1009 | ||
| <10 years | 537 (59.7%) | 83 (76.1%) | ||
| 10 ⩽ 25 years | 260 (28.9%) | 24 (22.0%) | ||
| >25 years | 103 (11.4%) | 2 (1.83%) | ||
| Acres | 0.001 | 1009 | ||
| <10 acres | 278 (30.9%) | 20 (18.3%) | ||
| 10 ⩽ 50 acres | 204 (22.7%) | 40 (36.7%) | ||
| >50 acres | 418 (46.4%) | 49 (45.0%) | ||
| Year-round employees | 0.048 | 1009 | ||
| 1–4 | 597 (66.3%) | 84 (77.1%) | ||
| 10–30 | 88 (9.78%) | 10 (9.17%) | ||
| >30 | 215 (23.9%) | 15 (13.8%) | ||
| Farming practice | 0.025 | 1009 | ||
| Conventional | 229 (25.4%) | 36 (33.0%) | ||
| Non-certified organic | 217 (24.1%) | 33 (30.3%) | ||
| Certified organic | 454 (50.4%) | 40 (36.7%) | ||
| Raise multiple animal species | 0.007 | 1009 | ||
| No | 152 (16.9%) | 7 (6.42%) | ||
| Yes | 748 (83.1%) | 102 (93.6%) | ||
| Owns cattle | 0.138 | 1009 | ||
| No | 228 (25.3%) | 20 (18.3%) | ||
| Yes | 672 (74.7%) | 89 (81.7%) | ||
| Owns small ruminants | 0.192 | 1009 | ||
| No | 326 (36.2%) | 47 (43.1%) | ||
| Yes | 574 (63.8%) | 62 (56.9%) | ||
| Owns poultry | 0.016 | 1009 | ||
| No | 69 (7.67%) | 1 (0.92%) | ||
| Yes | 831 (92.3%) | 108 (99.1%) | ||
| Owns swine | <0.001 | 1009 | ||
| No | 291 (32.3%) | 14 (12.8%) | ||
| Yes | 609 (67.7%) | 95 (87.2%) | ||
| Shared pasture | 0.011 | 953 | ||
| No | 301 (35.7%) | 53 (48.6%) | ||
| Yes | 543 (64.3%) | 56 (51.4%) | ||
| Shared barn | 0.113 | 953 | ||
| No | 714 (84.6%) | 99 (90.8%) | ||
| Yes | 130 (15.4%) | 10 (9.17%) | ||
| Vaccinate | <0.001 | 835 | ||
| No | 255 (34.1%) | 7 (8.05%) | ||
| Yes | 493 (65.9%) | 80 (92.0%) | ||
| Type of vaccine | 0.018 | 573 | ||
| Salmonella | 36 (7.30%) | 6 (7.50%) | ||
| E. coli O157 | 98 (19.9%) | 27 (33.8%) | ||
| Other | 359 (72.8%) | 47 (58.8%) | ||
| Veterinary care | <0.001 | 953 | ||
| No | 512 (60.7%) | 45 (41.3%) | ||
| Yes | 332 (39.3%) | 64 (58.7%) | ||
| Sample season | <0.001 | 1009 | ||
| Coastal summer | 149 (16.6%) | 19 (17.4%) | ||
| Fall | 85 (9.44%) | 2 (1.83%) | ||
| Hot summer | 406 (45.1%) | 34 (31.2%) | ||
| Spring | 167 (18.6%) | 33 (30.3%) | ||
| Winter | 93 (10.3%) | 21 (19.3%) | ||
| Daily min T (°C) | 11.6 (7.3–16.3) | 8.7 (2.9–11.6) | <0.001 | 1009 |
| Daily max T (°C) | 29 (24.1–36.4) | 25.3 (14.4–29.9) | <0.001 | 1009 |
| Average humidity (%) | 0.46 (0.46–0.46) | 0.55 (0.55–0.55) | 0.006 | 1009 |
| Type of sample | <0.001 | 1009 | ||
| Swaba | 252 (28.0%) | 12 (11.0%) | ||
| Faeces | 648 (72.0%) | 97 (89.0%) | ||
| Sourceb | 0.157 | 1009 | ||
| Poultry | 400 (44.4%) | 51 (46.8%) | ||
| Cattle | 95 (10.6%) | 18 (16.5%) | ||
| Small ruminant | 277 (30.8%) | 25 (22.9%) | ||
| Swine | 128 (14.2%) | 15 (13.8%) | ||
| Multisite farm | 0.064 | 1009 | ||
| Multisite | 593 (65.9%) | 82 (75.2%) | ||
| One site | 307 (34.1%) | 27 (24.8%) |
For continuous non-normally distributed variables, results are presented as: median (IQR) and P-values pertaining to a logistic regression output. For categorical variables, results are presented as: relative frequencies, percentages and P-values pertaining to a χ2 or Fisher's exact test.
a
Includes both surface and drag swabs.
b
Source = species of animal the sample was gathered from; poultry includes: other poultry, layer and broiler chickens; small ruminant includes: goats and sheep.