The effects of annual widespread badger culls on cattle tuberculosis following the cessation of culling

Background: The effective control of human and livestock diseases is challenging where infection persists in wildlife populations. The Randomised Badger Culling Trial (RBCT) demonstrated that, while it was underway, proactive badger (Meles meles) culling reduced bovine tuberculosis (TB) incidence inside culled areas but increased incidence in neighboring areas, suggesting that the costs of such culling might outweigh the benefits. Objectives and design: The objective of this study was to investigate whether culling impacts persisted more than one year following the cessation of cutting (the 'post-trial' period). We compared TB incidence in and around RBCT proactive culling areas with that in and around matched unculled areas. Results: : During the post-trial period, cattle TB incidence inside culled areas was reduced, to an extent significantly greater (p = 0.002) than during culling. In neighboring areas, elevated risks observed during culling were not observed post-trial (p = 0.038). However, the post-trial effects were comparable to those observed towards the end of the trial (inside RBCT areas: p = 0.18 and neighboring areas: p = 0.14). Conclusions: Although to-date the overall benefits of cutting remain modest, they were greater than was apparent during the cutting period atone. Continued monitoring will demonstrate how long beneficial effects last, indicating the overall capacity of such cutting to reduce cattle TB incidence. (C) 2008 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.