Adaptive interventions for advancing in situ wildlife disease management.

ABSTRACT

There is a critical need for advancements in disease management strategies for wildlife, but free-living animals pose numerous challenges that can hinder progress. Most disease management attempts involve fixed interventions accompanied by post hoc outcome assessments focused on success or failure. Though these approaches have led to valuable management advances, there are limitations to both the rate of advancement and amount of information that can be gained. As such, strategies that support more rapid progress are required. Sarcoptic mange, caused by epidermal infection with Sarcoptes scabiei mites, is a globally emerging and re-emerging panzootic that exemplifies this problem. The bare-nosed wombat (Vombatus ursinus), a marsupial endemic to southeastern Australia, is impacted by sarcoptic mange throughout its geographic range and enhanced disease management capabilities are needed to improve upon existing in situ methods. We sought to advance in situ wildlife disease management for sarcoptic mange in free-living bare-nosed wombats, implementing an adaptive approach using fluralaner (Bravecto, MSD Animal Health) and a structured process of learning and method-optimisation. By using surveillance of treated wombats to inform real-time management changes, we have demonstrated the efficacy of topically administered fluralaner at 45 and 85 mg/kg against sarcoptic mange. Importantly, we observed variation in the effects of 45 mg/kg doses, but through our adaptive approach found that 85 mg/kg doses consistently reduced mange severity. Through modifying our surveillance program, we also identified individual-level variation in wombat observability and used this to quantify the level of surveillance needed to assess long-term management success. Our adaptive intervention represents the first report of sarcoptic mange management with fluralaner in free-living wildlife and evaluation of its efficacy in situ. This study illustrates how adapting interventions in real time can advance wildlife disease management and may be applicable to accelerating in situ improvements for other host-pathogen systems.