Fine-Scale Landscape Epidemiology: Sarcoptic Mange in Bare-Nosed Wombats (Vombatus ursinus)

Abstract

Landscape epidemiology provides a valuable framework to interpret, predict, and manage spatiotemporal patterns of disease. Yet, owing to the difficulty of detecting pathogen occurrence in free-ranging wildlife, disentangling the factors driving disease dynamics remains a considerable challenge, particularly at fine spatial scales. Here, we investigated the fine-scale landscape epidemiology of sarcoptic mange—a visually apparent disease caused by the mite Sarcoptes scabiei—in bare-nosed wombats (Vombatus ursinus), by: (1) characterizing the distribution and density of wombats within the landscape and (2) examining the effect of environmental variation on the occurrence and apparent prevalence of mange. Wombats were heterogeneously distributed over 19.4 km of transect space (0.096–1.39 wombats ha−1) and seven months of time (increasing by a factor of 1.76). Wombat density was negatively associated with distance to vegetation cover, supporting a general propensity for wombats to occur and burrow near vegetation (native and exotic, excluding pasture). The apparent prevalence of mange varied spatially (3.1–37.5%), with the probability of disease greater in wombats with minimal vegetation and low-lying pans in their estimated home range. We observed trends of increased prevalence in areas with more burrows available per wombat and in individuals occurring near vegetation cover (although not within their home range). Wombat density and active burrow density did not influence the prevalence of mange. This research emphasizes the fine scale at which spatiotemporal patterns of disease can manifest and is the first to investigate the influence of host density for any species with indirect transmission of S. scabiei. Collectively, our results suggest that individuals inhabiting less optimal habitat (pasture) may be at greater risk of disease, or that diseased wombats may be competitively excluded from more optimal habitat (vegetated areas). We discuss implications for understanding and managing mange in wombats and cross-applicability to other mange-affected species with environmental transmission.