Pathogenic islands of refuge on the Great Plains: Using invasive eastern redcedar to understand the distribution of vector-borne pathogens in the southern Great Plains

Zoonotic and human pathogens transmitted by ticks and mosquitoes are a major source of disease in the United States. In the Great Plains region, there is a critical need to identify how land cover change affects vector abundance and diversity as well as risk for specific diseases. A major form of land cover change occurring in the Great Plains is woody plant encroachment (WPE) into previously open grasslands, and one of the predominant encroaching species is eastern red cedar (ERC). This study tested the hypotheses that ticks and mosquito communities and their likelihood of pathogen infection differed between ERC and other habitats in the southern Great Plains where the extent of WPE is 5-7x greater than elsewhere in the U.S. In regards to mosquitoes and WNV, we found significantly more Culex tarsalis in ERC than deciduous woodlands and grasslands as well as more WNV-infected Culex in ERC. Additionally, Aedes albopictus abundance increased directly with increased ERC cover in rural areas. Regarding ticks and tick-borne pathogens, we collected significantly more Amblyomma americanum and Dermacentor variabilis in ERC-encroached areas than in grassland and found significantly more Ehrlichia- and Rickettsia-infected A. americanum in ERC than grassland. Current studies are evaluating the impact of varying concentrations of ERC on tick abundance and diversity. Together, this connection of important vector-borne diseases with a predominant encroaching woody plant species suggests that land management approaches that facilitate WPE can increase human disease risk, and that active WPE control may be needed to reduce this risk.