Table 2.
Studies investigation an association between introduction of stock and bTB incident
| Study type | Study size (herds) | Country/year | Measure of risk | Comment, e.g. market/shows/dispersal | Ref. |
|---|---|---|---|---|---|
| Source of stock: type | |||||
| Case-control | 268 | England | Logistic regression: | RBCT triplets after initial pro-active badger cull and prior to Jan. 2001 | [71] |
| OR 3·26 (95% CI 1·71–6·21) | Markets | ||||
| OR 1·93 (95% CI 1·03–3·60) | Farm sales | ||||
| Retrospective cohort | 148 | England | Logistic regression: | RBCT from Oct. 2001 to Nov. 2004 | [6] |
| Response rate 40% | |||||
| Incidence of 50% over 3 years | |||||
| 24% restocked | |||||
| OR 1·95 (95% CI 1·05–3·63) | Markets | ||||
| Matched case-control | 218 | England and Wales | Conditional logistic regression: | Only confirmed cases. Analysis by region | [70] |
| OR 0·18 (95% CI 0·03–0·91) | Market (Taunton) | ||||
| Source of stock: bovine bTB history | |||||
| Retrospective cohort | 4742 | Ireland | Multivariate logistic regression (GEE): | Slaughterhouse cases excluded | [49] |
| OR 1·78 (95% CI 1·06–1·55) | Source herds had incident with SICCT.⩾8 reactors in previous 7 months compared to source herd not being under restrictions in last 7 months | ||||
| Matched case-control | 218 | England and Wales | Conditional logistic regression: | Case used confirmed and unconfirmed | [70] |
| OR 0·93 (95% CI 0·96–0·99) per additional 10% | Proportion sourced from 4yrly testing interval | ||||
| OR 1·90 (95% CI 1·0–3·62) | Sourcing from herd with incident within previous 2 years | ||||
| OR 8·48 (95% CI2·23–32·2) | Sourcing form herd with incident in previous 2 years (Stafford data only) | ||||
| Case-control | 18 670 | GB | OR 1·35 (95% CI 1·22–1·49) per every log increase in number of cattle introduced | Number of cattle brought form yearly testing interval compared to not purchasing | [97] |
| Type of stock introduced | |||||
| Case-control | 160 | Ireland, 1986–1990 | Conditional logistic regression: | Matched on herd size. Cases under restrictions for 12 months | [95] |
| OR 3·9 (95% CI 1·2–12·4) | Purchasing a bull in previous 5 years | ||||
| Comparative case-control | 229 | UK, 1995–1999 | OR 4·9 (95% CI 1·1–22·8) | Risk of persistent incident (>6 months) when introducing adult cows compared to store, calves and no introductions | [93] |
| Case-control | 102 781 | Ireland, 2006 | OR 1·04 (1·03–1·05) | Incident defined as the presence of one reactor to the SICCT. Introduction of stock >1 year in the previous year | [96] |
| Number of stock introduced | |||||
| Comparative case-control | 229 | UK, 1995–1999 | Multivariate logistic regression: | Risk of transient incident (<6 months) | [93] |
| OR 4·0 (95% CI 1·0–16·0) | Comparing introduction of >50 cows to <50 cows | ||||
| Case-control | 62 | Argentina, 2005–2007 | Logistic regression | Pastoral systems, herd size 50–500. Using caudal fold test. Cases >4 reactors, Controls no reactors in 24 months | [79] |
| OR 3·3 (95% CI 1·1–10·2) | >19 heifers introduced into the herd in 3 years | ||||
OR, Odds ratio; CI, confidence interval; RBCT, Randomized Badger Culling Trial; SICCT, single intradermal comparative cervical tuberculin test.