We assessed the federally endangered Amargosa vole (Microtus californicus scirpensis) and sympatric rodents for pathogen prevalence and infestation with Neotrombicula microti, a larval trombiculid mite, from December 2011- November 2012 in Tecopa Hot Springs, Inyo County, California. We found important pathogens in the Amargosa vole population including Toxoplasma gondii, Bartonella spp. and Borrelia burgdorferi sensu lato (SL) spp., and antibodies against Anaplasma phagocytophilum, Rickettsia spp., Borrelia spp., and T. gondii, while sympatric rodents had active infections with Bartonella spp. and Borrelia SL species. We collected Ixodes minor from captured rodents which is of interest since the study area is outside of the tick's reported range. Additionally, we found I. minor ticks infected with both A. phagocytophilum and Borrelia spp. showing a potential mode of pathogen import from outside the Amargosa ecosystem. The ninety-five percent confidence interval of true prevalence of N. microti infestation among voles was twenty seven to forty seven percent with females having a statistically greater prevalence of infestation than males. Histopathologic examination of vole tissue samples from N. microti infested ears revealed neutrophilic, lymphocytic, granulocytic and macrophage infiltration with hyperkeratosis, acanthosis, sub-corneal pustules and ulceration consistent across all levels of gross pathology. Both inflammation and necrosis were correlated with the extent of gross pathology, however no association was found between body condition score or animal weight. Our results for both pathogens and N. microti infestation do not support sympatric rodents as the cause of exposure to voles, however we recommend ongoing monitoring for disease and ectoparasites within the population as a critical component of Amargosa vole management and recovery efforts.

Providing an up-to-date introduction to biogeography, this textbook explains where different animals and plants live, examines why, and investigates how populations grow, interact and survive.