The prevalence of Lyme disease has increased substantially over the past twenty years with hotspots in both northern Illinois and southern Wisconsin. While previous research indicates Peromyscus leucopus is the primary reservoir of the etiologic agent—Borrelia burgdorferi, recent research reports B. burgdorferi in non-Peromyscine species. Of particular interest are species of the genus Microtus. Additionally, cases of Lyme disease have been reported from outside of the range of P. leucopus, including in habitat types not used by this species. However, minimal research has focused on identifying and verifying other potential small mammal reservoirs, and almost no studies have assessed this potential on a temporal scale. This study sought to identify the presence of potential non-Peromyscine reservoirs of Lyme disease in restored prairie ecosystems. To accomplish this, small mammals were trapped during the summers of 2014-2017. Upon capture animals were identified and fit with a unique RFID tag number. Any observed ticks were removed and a small tissue sample was collected from each individual. DNA was then extracted from tissues and they were screened for B. burgdorferi using PCR for both the OspB and FlaB loci with Borrelia specific primers.
Results/Conclusions
Three main species of prairie dependent rodents were captured during the course of the study in Boone County, Illinois: Microtus pennsylvanicus, Ictidomys tridecemlineatus, and Zapus hudsonius. Each species has tested positive for the presence of the spirochete annually since 2014 resulting in an overall infection rate of ~33%. Within species, Microtus showed the highest infection rate 41.8%, with both Ictidomys (25.6%) and Zapus having similar infection rates to each other. The abundance of individual species fluctuated annually, both intraspecifically and relative to each other. This is likely tied to the burn regime of the restoration. Additionally, Lyme infections rates also fluctuated with a drop in infection following a prairie burn in 2016 (21.6%) but infection rates rebounded a year later in 2017. Species specific infection rates also fluctuated over the course of the study with Ictidomys exhibiting an overall decrease in infection rate and the other species exhibiting fluctuations in both directions. Overall data indicate that several species likely represent substantial reservoirs at this site; further monitoring and assessment of disease transmission is needed to validate these conclusions.