Assessing the infection rates and pathogenesis of Borrelia burgdorferi in wild rodents and ticks in Western Maryland

Abstract

Abstract Lyme disease is the most prevalent vector-borne disease in the United States. The causative agent is the spirochete Borrelia burgdorferi. Many rodents are reservoir species that carry B. burgdorferi, through which immature ticks (Ixodes sp.) readily transmit the bacteria. Human cases of Lyme disease have dramatically increased over the past 10 years due to tick range expansion. Incidence has expanded from its New England origin into the Midwest and Mid-Atlantic. We hypothesized that Western Maryland is a prime candidate for B. burgdorferi expansion. To prepare, we sought to (1) determine the incidence of B. burgdorferi infection in wild rodent and tick populations in Western Maryland, (2) identify simple and quick methods for diagnosing B. burgdorferi infection in the field, and (3) gain insight into the pathogenesis of B. burgdorferi in wild rodent populations. DNA was extracted from 67 rodent blood samples and 202 ticks, collected from sites in Western Maryland. Approximately 35.14% of these samples tested positive for B. burgdorferi by PCR. Blood samples were tested for the presence of anti-B. burgdorferi antibody using SNAP 3Dx tests, a rapid ELISA-based veterinary diagnostic. Interestingly, the SNAP 3Dx tests were successful in identifying B. burgdorferi infection in both wild mice and chipmunks, suggesting that the capture antibody used in these canine tests is cross-reactive. Finally, whole B. burgdorferi bacteria were identified on frozen sections of wild mouse spleen by immunofluorescence. Bacteria were found throughout the red pulp and in splenic germinal centers of infected mice. Studies are underway to further characterize the infected cells in these samples.