The Lyme Disease Pathogen Has No Effect on the Survival of Its Rodent Reservoir Host

<div><p>Zoonotic pathogens that cause devastating morbidity and mortality in humans may be relatively harmless in their natural reservoir hosts. The tick-borne bacterium <i>Borrelia burgdorferi</i> causes Lyme disease in humans but few studies have investigated whether this pathogen reduces the fitness of its reservoir hosts under natural conditions. We analyzed four years of capture-mark-recapture (CMR) data on a population of white-footed mice, <i>Peromyscus leucopus</i>, to test whether <i>B</i>. <i>burgdorferi</i> and its tick vector affect the survival of this important reservoir host. We used a multi-state CMR approach to model mouse survival and mouse infection rates as a function of a variety of ecologically relevant explanatory factors. We found no effect of <i>B</i>. <i>burgdorferi</i> infection or tick burden on the survival of <i>P</i>. <i>leucopus</i>. Our estimates of the probability of infection varied by an order of magnitude (0.051 to 0.535) and were consistent with our understanding of Lyme disease in the Northeastern United States. <i>B</i>. <i>burgdorferi</i> establishes a chronic avirulent infection in their rodent reservoir hosts because this pathogen depends on rodent mobility to achieve transmission to its sedentary tick vector. The estimates of <i>B</i>. <i>burgdorferi</i> infection risk will facilitate future theoretical studies on the epidemiology of Lyme disease.</p>