The effect of wildlife host hotspots on bovine tuberculosis (bTB) risk dynamics in a disturbed landscape

Abstract Context Anthropogenic disturbance of ecosystems modulates zoonosis dynamics, but its effects in multi-host systems are poorly understood. Perturbation events, such as forest clearfelling, impact disease dynamics uniquely in each disease-host-ecology system. Objectives We investigated how clearfell, across a density gradient of badgers, fallow, red, and sika deer, affected the relative risk of bovine tuberculosis (bTB) breakdown (positive diagnostic test results) in cattle. We hypothesized that higher wildlife densities would increase the risk of bTB breakdown, and that clearfell would alter its spatio-temporal risk—reducing it in the short term when nearby but increasing it in the longer term as regenerating sites may attract wildlife. Methods We fit conditional logistic regressions to farm data ( n = 33,054) across Ireland to evaluate the effect of clearfell activities at different distances from farms (2–5 km) and time lags after clearfell (0–12 or 24–36 months). Results Higher densities of active badger setts and sika deer were associated with higher relative risk of breakdown in cattle. The sika-deer-breakdown association, however, was driven by one county with extremely high relative deer abundance. Clearfell activities were associated with decreased relative risk of breakdown when red and sika deer were present, potentially due to dispersal of deer away from farms. These patterns only existed when relative deer densities were high and as area (ha) of clearfell increased. Conclusions We provide evidence that clearfell may disturb wildlife, influencing breakdown risk in cattle herds and depending on wildlife species behaviour and population dynamics. Our study highlights the importance of monitoring and targeted management of deer populations in concert with other disease control goals.