Infectious diseases that affect wild and domestic animal and human populations are increasing in prevalence worldwide.  Most of these diseases have been associated with alteration of natural habitats by humans (e.g., agriculture, urbanization) that, presumably, causes increased stress in wild animal populations.  As wild animal populations become more stressed, they are also more likely to carry parasites and diseases.  As a result, humans living in areas near to disturbed habitats may have an increased risk of exposure to disease.  Dr. Claire Fuller and I are investigating the relationships among habitat disturbance, stress, immunocompetence, and disease in wild populations of Peromyscus leucopus (white-footed mouse).  We will determine and compare the levels of stress (as indicated by glucocorticoids) and dietary protein, levels of innate, humoral, and cell-mediated immune function, and prevalence of parasitic infections in wild white-footed mouse in small and large patches of habitat in winter and summer.  Our long-term objective is to produce and assess GIS-based models that predict the threat that habitat alteration poses to the health of wild mammal populations and the risk of disease incurred by nearby human populations.

Because species such as the white-footed mice live in close proximity of populated areas, humans and their domesticated animals, as well as other wild animals will be at greater risk of contracting disease from stressed animals.

We predict that as habitats become increasingly fragmented, there will be a reduction in reproduction and immunocompetence.    As immunocompetence is reduced, animals will become more susceptible to infections and disease.

Our test species, the white-footed mouse (Peromsycus leucopus) carries diseases such as Hanta Virus and Lyme disease, both of which are very hazardous to humans.

Through the research of a graduate student (Cynthia Hornung), we have already documented that there are seasonal changes in the mass of the spleen, an organ important to immune function, and in diet composition.  The spleen of adult males (below- blue histogram bars) is enlarged in white-footed mice captured in the fall compared with other seasons.  The spleen is also greatly enlarged in lactating females (below - yellow histogram bar).   The amount of protein in the diet peaks during summer in males, probably due to the abundance of insects available.  Ingestion of fiber, as a percent of the total diet, is greatest in males in spring as tender plant shoots that are easily digested become available.  Differences in parameters such as these may occur when comparing mice from small and large habitat fragments.
 
 

Figure 1.  Seasonal measurements of the dry mass of the spleen in adult male white-footed mice.  Values are also given for lactating females (yellow bar) captured in summer.

Figure 2.  Seasonal estimates of the amount of dietary fiber and protein in adult male white-footed mice.  Values are also given for lactating females captured during