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

Anthropogenic disturbance of ecosystems and wildlife can modulate zoonosis emergence and transmission, but is difficult to quantify and poorly understood, especially in multi-host systems. Perturbation events, such as forest clearfelling, impact disease dynamics uniquely in each disease-host-ecology system. Focusing on bovine tuberculosis (bTB) in Ireland, we investigated how clearfell, in a wildlife density gradient ranging from absence to high relative density of badgers ( Meles meles ), fallow deer ( Dama dama ), red deer ( Cervus elaphus ), and sika deer ( Cervus nippon ), affected the relative risk of bTB breakdown in cattle herds. We fit conditional logistic regression models to cattle farm data ( n  = 33,054) across a national landscape at four spatio-temporal scales to evaluate the effect of clearfell activities at different distances (within 2 or 5 km from farms) and time lags (0–12 or 24–36 months after clearfell). Higher densities of active badger setts were associated with higher relative risk of breakdown in cattle. Higher relative densities of sika deer were also associated with higher relative risk of breakdown, identifying them as a bTB host of interest in Ireland; however, this association was driven by one county with extremely high relative abundance of sika deer. Clearfell occurring within 5 km of farms 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; these data did not provide any evidence for an association between deer density with relative risk of breakdown in cattle when deer were present at reduced and potentially sustainable relative densities. We provide evidence that clearfell may disturb wildlife, influencing breakdown risk in cattle herds in a manner dependant on wildlife species behaviour and population dynamics. Our study also highlights the importance of monitoring and targeted management of deer populations in concert with other disease control eradication goals.