Effects of environmental factors on pathogen exposure and transmission in wild rodent populations

Abstract

Anthropogenic land-use change is altering ecosystems across the globe and has been implicated as a major factor increasing the spillover of zoonotic diseases from wildlife into human populations. Wild rodents are of particular importance for spillover as they host the largest diversity of zoonotic pathogens of any mammalian order. Moreover, rodent hosts of zoonotic pathogens have been found to increase in abundance in anthropogenic landscapes. In my dissertation, I investigate the effects of environmental factors related to anthropogenic land-use change on pathogen prevalence and transmission in wild rodent populations. Using an observational field study across landscape and habitat types, I broadly investigate the effects of anthropogenic development on the prevalence of zoonotic bacterial pathogens in wild Peromyscus mice (Chapter 1). I then turn to finer spatial scales to consider how spatial overlap can be used to approximate transmission in wildlife populations (Chapter 2). Using wild bank voles (Clethrionomys glareolus) as a model system, I leverage a replicated, experimental field study to quantify the effects of food supplementation and helminth macroparasite removal on vole space use and spatial overlap to approximate transmission opportunities (Chapter 3). Finally, I test how spatial overlap predicts infection of an endemic viral pathogen and examine whether the relationship between spatial overlap and infection is influenced by food abundance and macroparasite infection (Chapter 4). My research indicates that agricultural development may increase the prevalence of zoonotic bacterial pathogens in wild rodents. Further, I show that environmental factors alter the space use of wild rodents and that both environmental conditions and host traits are important to predict how spatial overlap affects transmission of an endemic pathogen. As such, my dissertation research has contributed empirical evidence that shows how environmental conditions alter zoonotic pathogen prevalence and transmission in wild rodent populations. This represents an important step forward in our ability to quantify the effects of anthropogenic land-use change on disease dynamics in wildlife, advancing our ability to understand and predict transmission dynamics and control spillover potential from wildlife into human populations.