Bartonella infections are widely distributed in rodents of many species with high prevalences and high genetic diversity. Some rodent-associated bartonellae are also associated with human illnesses. After reviewing the current knowledge of bartonellae (Chapter 1), this dissertation focuses on analyses of associations of bartonellae with their rodent hosts in order to understand how dynamics and diversity of bartonellae are regulated by parameters of rodent communities and populations (Chapter 2).

Chapter 3 describes the relationship between bartonella prevalence and structure of rodent community and points out that bartonella prevalence is negatively correlated with diversity of rodent community, suggesting a dilution effect. Chapter 4 describes temporal dynamics of bartonella prevalence during rodent population cycles, successive bartonella infection in individual rodents, and the effects of some rodent population parameters, such as rodent age, on bartonella prevalence and level of bacteremia. Chapter 5 describes host-specificity of bartonellae in their rodent hosts and concludes that host-specificity occurs mostly at the level of the genus of the rodent host. Bartonellae occasionally can “jump” to non-specific host rodents. The northern grasshopper mouse, an exception, acquires non-specific bartonella strains commonly, and hosts multiple typical bartonella strains. Chapter 6 describes spatial distribution and deviation of genetic variants of Bartonella species between colonial black-tailed prairie dogs, pointing out the effect of landscape features.

This research has provided data to help understand the ecological characteristics of bartonellae. Knowing information of rodent community and population, it is possible to predict bartonella dynamics and composition of bartonella strains in a particular rodent community and/or population. This is of epidemiological significance with regard to the public health concern of bartonellosis as an emerging disease.