It is widely recognized that invasive species pose a significant threat to native biodiversity. However, ecologists have only begun studying the indirect effects of biological invasions on transmission of parasites and pathogens that cause disease in humans. For example, habitat preference by white-tailed deer (Odocoileus virginianus) for the invasive vine honeysuckle (Lonicera sp.) has resulted in higher densities of lone star ticks (Amblyomma americanum) infected with Ehrlichia chaffeensis and E. ewingii in honeysuckle-invaded areas than in areas from which honeysuckle had been removed. Honeysuckle is among the most aggressive invasive species in North America and is recognized as an important forage species for white-tailed deer. White-tailed deer are a keystone host for the lone star tick, are an important reservoir for Ehrlichia chaffeensis and E. ewingii. We analyzed field data from the National Oceanic and Atmospheric Administration, the US Geological Survey, and the US Forest Service to develop a spatially-explicit, agent-based, simulation model projecting invasion of Japanese honeysuckle into the southern United States as a function of climate, landscape, and forest community characteristics. We then drew upon results of our range expansion simulations to associate increase in incidence risk of ehrlichiosis over the next two decades in southern United States.
Results/Conclusions
Our results indicated that probability of plant invasion was positively associated with elevation, adjacency to water bodies, mean daily maximum temperature, site productivity and private land ownership, and was negatively associated with slope, stand age, artificial regeneration, distance to the nearest road and fire disturbance. Our projections suggested the total area invaded would increase from 1.36 to ≈31.39% in southern United States. The incident cases of ehrlichiosis were correlated positively with extent of honeysuckle invasion, most likely due primarily to preferred use of honeysuckle patches by white-tailed deer, resulting in higher lone start tick population, and secondarily from increased survivorship of off-host tick life stages in patches of dense honeysuckle.