Habitat availability alters the relative risk of a bovine tuberculosis breakdown in the aftermath of a commercial forest clearfell disturbance.
Abstract
Human modification of landscapes and associated disturbances may facilitate the emergence and spread of zoonotic diseases. Policy-makers need better understanding of the link between anthropogenic disturbances and wildlife disease hosts at the interface of human society and the natural environment, for example agriculture, forestry and aquaculture. Empirical research is strongly needed for the control of novel zoonoses which might emerge, as well as the management of existing zoonoses with significant economic repercussions such as bovine tuberculosis (bTB). We aimed to examine the link between ecological disturbance and relative bTB risk using Ireland as a case study. We analysed clearfell forestry operations and assessed bTB breakdowns within cattle farms across different spatio-temporal scales over multiple years, examining how ecological conditions may modulate this relationship using conditional logistic regression models. We found a significant effect of the interaction between the extent of clearfell forestry removed and the extent of natural grassland and mixed forestry present on relative bTB risk. This interaction was dynamic, leading to an increase or decrease of the relative bTB risk depending on where (between 2 and 6 km from the farm) and when (between 0 and 36 months prior to the bTB outbreak) the clearfell operations occurred. Our study provides empirical evidence of the link between mechanised forestry operations and fluctuating relative bTB risk in cattle farms, although the mechanism behind it is yet to be elucidated. Given our data, we hypothesise that wildlife hosts may abandon the area subjected to clearfell when disturbance is highest (during active operations and shortly afterward) but are subsequently attracted back to the site as they regenerate, potentially affecting the contact rates with livestock and thus, relative bTB risk. Synthesis and applications. Our analysis demonstrates that landscape modification is correlated with a change in relative bovine tuberculosis (bTB) risk that is dynamic in time and space. Understanding that the effect of landscape change is transient allows managers to understand the risk for neighbouring farms and inform policy accordingly. Landscape-level studies are necessary to unveil subtle-ecological processes, shifting research and management efforts away from cattle herd-centric policy and toward macroecological surveillance of wildlife hosts and longitudinal assessment of bTB risk.