Vaccinating badgers in a post-cull landscape; insights from the field.
In 2010 the BadgerBCG vaccine was licenced for use in badgers in the United Kingdom to reduce the severity of Mycobacterium bovis infection, and hence the risks of onward transmission to cattle. To date badger vaccination in the United Kingdom has been deployed at a relatively limited spatial scale (compared to the large-scale badger culls) and almost exclusively in high-density badger populations which have not been recently culled. UK Government policy direction has moved towards the wider rollout of badger vaccination as an exit strategy following culling. Field resources required to carry out vaccination in undisturbed badger populations are well documented, but levels of effort are unlikely to be directly transferable to previously culled populations where badger density and social behaviour may be markedly different. We present an evidence-based assessment of the likely effort required to vaccinate badger populations that have recently been culled, drawing on data from past culling operations, vaccination operations in a previously culled area and the practical field experiences of expert badger trappers. Trapping efficiency declined over successive years of industry-led culling, however, this effect was not consistently noted in the government-run randomized badger culling trial (RBCT). Fewer badgers were removed using cage trapping (compared to 'controlled shooting') in the latter years of intensive industry-led culls. When trapping badgers for vaccination in areas that had previously been culled, highly experienced government field staff adapted their practices in response to the lower density and likely more mobile residual population. A longer and more variable pre-baiting period was expected and there was a greater reliance on higher levels of skill and experience in interpreting field signs and trapping effectively in such populations.