Spending time outdoors is an important component of the lifestyle valued so highly by many of the residents of Nevada. The image of squirrels hopping by a cabin or a chipmunk begging for food in a picnic area is common, and relaxing. Although these forest denizens belong in the natural landscape, they also serve to maintain diseases that are transmitted to humans and domestic animals that share these habitats.
Recent closures of state parks due to bubonic plague outbreaks serve as good examples of potential risks posed to human health and the loss to rural economies due to decreased tourism. Increased numbers of rodents often lead to higher rates of infection with zoonotic diseases such as hantavirus and plague. Chipmunks are commonly found in close association with humans in campgrounds and around rural cabins.
Research conducted by University of Nevada, Reno indicates that in the Sierra Nevada ecosystem, chipmunks are commonly infected by relapsing fever spirochetes and that chipmunks serve as an important link in disease transmission to humans.
The disease, relapsing fever, has affected citizens of Nevada and California alike and is transmitted to individuals through the bite of an infected tick. Wild rodents, especially chipmunks serve both to maintain tick populations and as reservoirs for the bacteria, Borrelia hermsii, which causes relapsing fever in humans.
Human induced changes to the natural environment, such as woodpiles, trash cans and homes uninhabited during the winter may serve to benefit wild rodents resulting in higher rodent survival and reproduction. Further research conducted by University of Nevada, Reno indicates that chipmunks serve as a reservoir for relapsing fever and appear to be in higher densities around rural/summer cabins than in areas without human habitation. The high rodent densities help to amplify the potential for disease transmission to humans.
In order to understand how rodent survival, reproduction and recruitment can affect the prevalence of disease around human habitations, this project will use chipmunks as model organisms to understand the transmission dynamics that occur to maintain relapsing fever in nature. Through the use of genetic techniques, investigator will test whether human habitation influences rodent dispersal by testing paired sites in Nevada and California that are endemic for relapsing fever. Chipmunk DNA from study sites where humans live for part of the year will be compared to chipmunk DNA collected from endemic sites in which humans recreate but do not live. We plan to test whether chipmunk dispersal is altered by human habitation and whether this influences the ecological maintenance of relapsing fever.