Modelling the effectiveness of measures applied in zones dedicated to stop the spread of African Swine Fever in wild boar when bordering with a region of limited control

Abstract

African Swine Fever (ASF) is an infectious lethal disease affecting domestic pigs and wild boar. In the EU the infection perpetuates predominantly in wild boar populations. ASF control comprises wild boar population reduction measures, e.g. pre-emptive culling in delineated zones, called white zones (WZ). These WZ are placed geographically adjacent to an area with ASF circulating in wild boar (ASF positive area). The ideal WZ would be depopulated of wild boar without possibility of recolonization. However, live wild boar may still be present in the WZ after its implementation and the functionality of the WZ inherently foresees ASF entering it. But the spread of the infection is expected to stop within an effective WZ. The principal approach was established in the EU with regards to focal introductions. Here the special case is considered when the WZ approach is applied adjacent to an (potentially large) area with limited ASF control. The results of the spatially explicit individual-based simulations in different EU landscapes demonstrate that the WZ strategy becomes more complicated when applied in adjacency to areas with limited control. The failure rate and the hunting effort to implement the WZ increases compared to the focal scenario. The three WZ parameters, width, distance to core area and culling target density are tested in both situations and combined with carcass removal and fencing to facilitate effect comparison. Proactive approaches are simulated and the outcome was found to be dominated from the landscape and/or the WZ parameters chosen.