title: Borrelia burgdorferi promotes the establishment of Babesia microti in the northeastern United States.
abstract: Babesia microti and Borrelia burgdorferi, the respective causative agents of human babesiosis and Lyme disease, are maintained in their enzootic cycles by the blacklegged tick (Ixodes scapularis) and use the white-footed mouse (Peromyscus leucopus) as primary reservoir host. The geographic range of both pathogens has expanded in the United States, but the spread of babesiosis has lagged behind that of Lyme disease. Several studies have estimated the basic reproduction number (R0) for B. microti to be below the threshold for persistence (<1), a finding that is inconsistent with the persistence and geographic expansion of this pathogen. We tested the hypothesis that host coinfection with B. burgdorferi increases the likelihood of B. microti transmission and establishment in new areas. We fed I. scapularis larva on P. leucopus mice that had been infected in the laboratory with B. microti and/or B. burgdorferi. We observed that coinfection in mice increases the frequency of B. microti infected ticks. To identify the ecological variables that would increase the probability of B. microti establishment in the field, we integrated our laboratory data with field data on tick burden and feeding activity in an R0 model. Our model predicts that high prevalence of B. burgdorferi infected mice lowers the ecological threshold for B. microti establishment, especially at sites where larval burden on P. leucopus is lower and where larvae feed simultaneously or soon after nymphs infect mice, when most of the transmission enhancement due to coinfection occurs. Our studies suggest that B. burgdorferi contributes to the emergence and expansion of B. microti and provides a model to predict the ecological factors that are sufficient for emergence of B. microti in the wild.
authors.affiliation: School of Mathematical and Geospatial Sciences, RMIT University, Melbourne, Australia.
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Dunn
authors.affiliation: Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America; Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Krause
authors.affiliation: School of Mathematical and Geospatial Sciences, RMIT University, Melbourne, Australia.
authors.forename: Stephen
authors.initials: S
authors.lastname: Davis
authors.affiliation: Division of Geographic Medicine and Infectious Diseases, Tufts Medical Center, Boston, Massachusetts, United States of America.
authors.forename: Edouard G
authors.initials: EG
authors.lastname: Vannier
authors.affiliation: Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America.
authors.forename: Meagan C
authors.initials: MC
authors.lastname: Fitzpatrick
authors.affiliation: Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America.
authors.forename: Lindsay
authors.initials: L
authors.lastname: Rollend
authors.affiliation: Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Alexia A
authors.initials: AA
authors.lastname: Belperron
authors.affiliation: Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America; Department of Ecology, Evolution and Environmental Biology, Columbia University, New York, New York, United States of America.
authors.forename: Sarah L
authors.initials: SL
authors.lastname: States
authors.affiliation: School of Mathematical and Geospatial Sciences, RMIT University, Melbourne, Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Stacey
authors.affiliation: Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Linda K
authors.initials: LK
authors.lastname: Bockenstedt
authors.affiliation: Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America.
authors.forename: Durland
authors.initials: D
authors.lastname: Fish
authors.affiliation: Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America; Department of Ecology, Evolution and Environmental Biology, Columbia University, New York, New York, United States of America.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Diuk-Wasser
mesh_terms: D000818:Animals; D041001:Babesia microti / Q000472:pathogenicity*; D001404:Babesiosis / Q000635:transmission*; D025065:Borrelia burgdorferi / Q000472:pathogenicity*; D060085:Coinfection / Q000382:microbiology / Q000469:parasitology; D018884:Ixodes / Q000382:microbiology / Q000469:parasitology; D009511:New England; D010542:Peromyscus / Q000382:microbiology / Q000469:parasitology