Background: In the British Isles, control of cattle tuberculosis (TB) is hindered by persistent infection of wild badger (Meles
meles) populations. A large-scale field trial—the Randomised Badger Culling Trial (RBCT)—previously showed that
widespread badger culling produced modest reductions in cattle TB incidence during culling, which were offset by elevated
TB risks for cattle on adjoining lands. Once culling was halted, beneficial effects inside culling areas increased, while
detrimental effects on adjoining lands disappeared. However, a full assessment of the utility of badger culling requires
information on the duration of culling effects.
Methodology/Principal Findings: We monitored cattle TB incidence in and around RBCT areas after culling ended. We
found that benefits inside culled areas declined over time, and were no longer detectable by three years post-culling. On
adjoining lands, a trend suggesting beneficial effects immediately after the end of culling was insignificant, and disappeared
after 18 months post-culling. From completion of the first cull to the loss of detectable effects (an average five-year culling
period plus 2.5 years post-culling), cattle TB incidence was 28.7% lower (95% confidence interval [CI] 20.7 to 35.8% lower)
inside ten 100 km2 culled areas than inside ten matched no-culling areas, and comparable (11.7% higher, 95% CI: 13.0%
lower to 43.4% higher, p = 0.39) on lands #2 km outside culled and no-culling areas. The financial costs of culling an
idealized 150 km2 area would exceed the savings achieved through reduced cattle TB, by factors of 2 to 3.5.
Conclusions/Significance: Our findings show that the reductions in cattle TB incidence achieved by repeated badger culling
were not sustained in the long term after culling ended and did not offset the financial costs of culling. These results,
combined with evaluation of alternative culling methods, suggest that badger culling is unlikely to contribute effectively to
the control of cattle TB in Britain.