Borrelia burgdorferiInfection in a Natural Population ofPeromyscus LeucopusMice: A Longitudinal Study in an Area Where Lyme Borreliosis Is Highly Endemic

Blood samples from Peromyscus leucopus mice captured at an enzootic site in Connecticut were examined for antibodies to and DNA of Borrelia burgdorferi, to characterize the dynamics of infection in this reservoir population. From trappings conducted over the course of 2 transmission seasons, 598 (75%) of 801 serum samples from 514 mice were found to be positive by enzyme immunoassay. Seropositivity correlated with date of capture and mouse age, was similar among locations within the site, increased from 57% to 93% over the course of the transmission season, and was associated with antibodies to outer surface protein (Osp) C, but not to OspA. Longitudinal samples from 184 mice revealed an incidence of 0.2 cases/mouse/week. Nineteen (10%) of 187 samples were found by polymerase chain reaction to be positive for B. burgdorferi, and, of those, 14 (74%) were found to be seropositive. Nearly the entire population of P. leucopus mice became infected with B. burgdorferi by late August, coinciding with the peak activity period of host-seeking larvae uninfected with the spirochete Ixodes scapularis, thereby perpetuating the agent through succeeding generations of ticks.