Human babesiosis is a rapidly emerging tick-borne zoonosis in the United States caused by the protozoan Babesia microti and transmitted by Ixodes scapularis, the Lyme disease vector. Unlike Lyme disease, babesiosis is a potentially fatal disease and poses a threat to blood transfusion recipients. In the Northeast, both Lyme disease and babesiosis were originally restricted to coastal New England.
While Lyme disease has expanded dramatically over the past thirty years and now is endemic from Maine to Virginia, babesiosis cases appears to be expanding at a slower rate for reasons that are not understood. This differential spread provides a unique opportunity to examine factors driving pathogen emergence by comparing these species’ natural history and transmission dynamics. Furthermore, because B. microti encounters a large proportion of host populations already infected with B. burgdorferi throughout its geographic expansion, the goal of this study is to investigate how pathogen interactions at the individual, population, and community levels influence B. microti invasion patterns and enzootic prevalence.