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Abstract
Babesia microti is the primary etiological agent of human babesiosis (Vannier & Krause). Although it shares the same tick vector and mammal reservoirs as B. burgdorferi, the causative agent of Lyme disease, the geographic extent of B. microti is limited to a subset of the range of B. burgdorferi (Diuk-Wasser et al.). Despite the slower spread of B. microti, it is equally prevalent in ticks in certain areas where both B. burgdorferi and B. microti have been endemic for long periods. The slower rate of B. microti expansion as compared to B. burgdorferi has been attributed to a lower efficiency of transmission for B. microti (Dunn et al.), however, this alone does not explain the similar prevalence of both microbes in areas long endemic to both pathogens. This study assesses the relative importance of ecological conditions and pathogen interactions in B. microti and B. burgdorferi prevalence in I. scapularis nymphs from a sample of 1514 nymph-stage ticks collected at 35 sites in eastern Connecticut, western Rhode Island, and southern Massachusetts. Our results show that the odds of a tick testing positive for B. microti is not associated to the density of nymphal ticks or the prevalence of B. burgdorferi at the site level, but it is associated with the presence of B. burgdorferi in the individual tick and the geographic location of the tick. None of the covariates tested showed a strong association with the odds of a tick testing positive for B. burgdorferi
