Table 2.
Results from the multivariable survival analyses performed on herds with bovine tuberculosis (bTB) breakdowns declared in 2010–2017 in Castilla y Leon.
| Variable (number of herds with information) | Levels | Hazard ratio (95% CI) | P-value |
|---|---|---|---|
| Median herd size in the year the bTB breakdown started (n = 3,447) | Small | 1 (NA) | – |
| Medium | 0.73 (0.7–0.8) | <0.001 | |
| Large | 0.6 (0.5–0.7) | <0.001 | |
| Number of incoming animals in the 3 years prior to the start of the bTB breakdown (n = 3,196) | 0 | 1.17 (1–1.3) | 0.007 |
| 1 | 1.06 (0.9–1.2) | 0.356 | |
| 2–4 | 1.19 (1.1–1.3) | 0.001 | |
| >4 | 1 (NA) | – | |
| County-level herd prevalence in the year prior to the start of the bTB breakdown (n = 3,017) | 0 | 1 (NA) | – |
| 0.01–0.06 | 0.92 (0.8–1) | 0.114 | |
| 0.061–0.1 | 0.86 (0.8–0.9) | 0.017 | |
| 0.11–0.2 | 0.74 (0.6–0.9) | <0.001 | |
| 0.21–1 | 0.68 (0.5–0.9) | 0.005 | |
| Production type (n = 3,454) | Beef/fattening | 1 (NA) | – |
| Bullfighting | 1.09 (0.7–1.6) | 0.666 | |
| Dairy/mixed | 1.04 (0.9–1.2) | 0.555 | |
| Province (n = 3,454) | Avila | 1 (NA) | – |
| Burgos | 0.76 (0.6–0.9) | 0.017 | |
| Interaction with time | Yes +a | ||
| Leon | 0.93 (0.8–1.1) | 0.496 | |
| Interaction with time | No | ||
| Palencia | 1.29 (0.9–1.8) | 0.116 | |
| Interaction with time | No | ||
| Salamanca | 0.85 (0.7–1) | 0.036 | |
| Interaction with time | Yes + | ||
| Segovia | 0.93 (0.7–1.1) | 0.487 | |
| Interaction with time | Yes + | ||
| Soria | 0.56 (0.4–0.7) | <0.001 | |
| Interaction with time | Yes + | ||
| Valladolid | 0.43 (0.3–0.7) | <0.001 | |
| Interaction with time | No | ||
| Zamora | 0.92 (0.7–1.2) | 0.515 | |
| Interaction with time | Yes + | ||
| Number of SIT reactors in the disclosing test (n = 3,454) | 0 | 0.61 (0.5–0.7) | <0.001 |
| 1 | 1 (NA) | – | |
| 2–4 | 0.93 (0.8–1.0) | 0.139 | |
| ≥5 | 0.74 (0.6–0.9) | <0.001 | |
| Number positive to bacteriology in the disclosing test (n = 3,454) | 0 | 1 (NA) | – |
| 1 | 0.15 (0.1–0.2) | <0.001 | |
| Interaction with time | Yes + | ||
| 2 | 0.12 (0.1–0.2) | <0.001 | |
| Interaction with time | Yes + | ||
| ≥3 | 0.09 (<0.1–0.1) | <0.001 | |
| Interaction with time | Yes + | ||
| Number of days between the disclosing and follow-up tests (n = 3,417) | 0–70 | 1 (NA) | – |
| 71–90 | 0.75 (0.6–0.9) | <0.001 | |
| Interaction with time | Yes + | ||
| 91–124 | 0.44 (0.4–0.5) | <0.001 | |
| Interaction with time | Yes + | ||
| >124 | 0.25 (0.2–0.3) | <0.001 | |
| Interaction with time | Yes + |
a
+ Interaction with time significantly increased the value of the coefficient.
SIT, single intradermal test.