Abstract
The objective was to measure the association between badger culling and bovine tuberculosis (TB) incidents in cattle herds in three areas of England between 2013–2017 (Gloucestershire and Somerset) and 2015–2017 (Dorset). Farming industry-selected licensed culling areas were matched to comparison areas. A TB incident was detection of new Mycobacterium bovis infection (post-mortem confirmed) in at least one animal in a herd. Intervention and comparison area incidence rates were compared in central zones where culling was conducted and surrounding buffer zones, through multivariable Poisson regression analyses. Central zone incidence rates in Gloucestershire (Incidence rate ratio (IRR) 0.34 (95% CI 0.29 to 0.39, p < 0.001) and Somerset (IRR 0.63 (95% CI 0.58 to 0.69, p < 0.001) were lower and no different in Dorset (IRR 1.10, 95% CI 0.96 to 1.27, p = 0.168) than comparison central zone rates. The buffer zone incidence rate was lower for Gloucestershire (IRR 0.64, 95% CI 0.58 to 0.70, p < 0.001), no different for Somerset (IRR 0.97, 95% CI 0.80 to 1.16, p = 0.767) and lower for Dorset (IRR 0.45, 95% CI 0.37 to 0.54, p < 0.001) than comparison buffer zone rates. Industry-led culling was associated with reductions in cattle TB incidence rates after four years but there were variations in effects between areas.
Highlights
Industry-led badger culling as a policy to control bovine tuberculosis (TB) in cattle was introduced by the Department for Environment, Food & Rural Affairs in England in 2013
This analysis showed a statistically significant decrease in Officially Tuberculosis Free Withdrawn (OTF-W) incidence in both culled areas compared to areas with no culling
The results from this study showed that there were statistically significant decreases in cattle TB incidence in the Gloucestershire and Somerset intervention areas after four years of culling, consistent with an earlier analysis based on two years of badger culling[11]
Summary
Current badger culls are carried out by the farming industry, and involve a combination of cage trapping and controlled shooting (where free roaming badgers are shot at night), with effort spread over a period of six weeks or more It is unclear whether current badger culls would produce similar changes in cattle TB incidence to those observed during the RBCT. The analysis of effects in cattle herds over two years since badger culling began in Gloucestershire and Somerset has already been reported[11] This analysis showed a statistically significant decrease in Officially Tuberculosis Free Withdrawn (OTF-W) incidence in both culled areas compared to areas with no culling. An increase in incidence was observed in the two km buffer zone around the Somerset culled area (IRR 1.38, 95% CI 1.09 to 1.75) but not in Gloucestershire (IRR 0.91 95% CI 0.77 to 1.07)
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