Sterilization as an alternative strategy to control wildlife diseases: bovine tuberculosis in European badgers as a case study

Sterilization has rarely been considered as an alternative to culling or va ccination to control wildlife diseases. Disease control by sterilization, a s by culling, has most promise when the host's ability for compensatory gro wth following the removal of density-dependent inhibitions is limited, and when moderate reductions in population density cause disproportionately lar ge reductions in disease prevalence, or even eliminate the disease. For man y host/disease examples this will not be the case and vaccination may have overwhelming advantages or may be the only practical option. The impact of sterilization on host density and disease prevalence will develop relativel y slowly because sterilization can prevent the recruitment of only one age- cohort at a time. Moreover, unless there is vertical transmission, this age -cohort will consist only of susceptibles. Culling, on the contrary, remove s infected as well as susceptible animals. However, for certain disease/hos t examples, the relative effectiveness of the different control strategies may be altered considerably if their variable effects on the probability of disease transmission are taken into account. Social perturbation or stress could render certain culling strategies ineffective or even counter-produc tive. Depending on how disease dynamics are influenced by the host's age-st ructure and reproductive investment; fertility control could offer epidemio logical advantages that have been ignored by most disease/host models. We i llustrate some of these principles by investigating the theoretical and pra ctical feasibility of an hypothetical sterilization campaign to control bov ine tuberculosis in badgers (and hence cattle) in Britain.