title: Prevalence, Distribution, and Development of an Ecological Niche Model of Dermacentor variabilis Ticks Positive for Rickettsia montanensis.
abstract: Rickettsia montanensis has long been considered a nonpathogenic member of the spotted fever group rickettsiae. However, the infection potential of R. montanensis is being revisited in light of its recent association with a case of human infection in the United States and the possibility that additional cases may have been misdiagnosed as Rocky Mountain spotted fever. To this end, DNA was extracted from American dog ticks (Dermacentor variabilis) removed from Department of Defense (DoD) personnel and their dependents at DoD medical treatment facilities (MTFs) during 2002-2012 (n = 4792). These 4792 samples were analyzed for the presence of R. montanensis (n =  36; 2.84%) and all vector DNA was confirmed to be of D. variabilis origin using a novel Dermacentor genus-specific quantitative real-time polymerase chain reaction procedure, Derm, and a novel Dermacentor species multilocus sequence typing assay. To assess the risk of R. montanensis infection, the positive and negative samples were geographically mapped utilizing MTF site locations. Tick localities were imported into a geographical information systems (GIS) program, ArcGIS, for mapping and analysis. The ecological niche modeling (ENM) program, Maxent, was used to estimate the probability of tick presence in eastern United States using locations of both R. montanensis-positive and -negative ticks, climate, and elevation data. The ENM for R. montanensis-positive D. variabilis estimated high probabilities of the positive ticks occurring in two main areas, including the northern Midwest and mid-Atlantic portions of the northeastern regions of United States, whereas the R. montanensis-negative D. variabilis tick model showed a wider estimated range. The results suggest that R. montanensis-positive and -negative D. variabilis have different ranges where humans may be at risk and are influenced by similar and different factors.
authors.affiliation: 1 Viral and Rickettsial Diseases Department, Naval Medical Research Center , Silver Spring, Maryland.|2 Henry M. Jackson Foundation , Bethesda, Maryland.
authors.forename: Heidi K
authors.initials: HK
authors.lastname: St John
authors.affiliation: 1 Viral and Rickettsial Diseases Department, Naval Medical Research Center , Silver Spring, Maryland.|2 Henry M. Jackson Foundation , Bethesda, Maryland.
authors.forename: Melissa L
authors.initials: ML
authors.lastname: Adams
authors.affiliation: 2 Henry M. Jackson Foundation , Bethesda, Maryland.|3 Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences , Bethesda, Maryland.
authors.forename: Penny M
authors.initials: PM
authors.lastname: Masuoka
authors.affiliation: 1 Viral and Rickettsial Diseases Department, Naval Medical Research Center , Silver Spring, Maryland.
authors.forename: Johanna G
authors.initials: JG
authors.lastname: Flyer-Adams
authors.affiliation: 1 Viral and Rickettsial Diseases Department, Naval Medical Research Center , Silver Spring, Maryland.|2 Henry M. Jackson Foundation , Bethesda, Maryland.
authors.forename: Ju
authors.initials: J
authors.lastname: Jiang
authors.affiliation: 1 Viral and Rickettsial Diseases Department, Naval Medical Research Center , Silver Spring, Maryland.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Rozmajzl
authors.affiliation: 4 Laboratory Sciences, Army Public Health Center , Aberdeen Proving Ground, Maryland.
authors.forename: Ellen Y
authors.initials: EY
authors.lastname: Stromdahl
authors.affiliation: 1 Viral and Rickettsial Diseases Department, Naval Medical Research Center , Silver Spring, Maryland.|3 Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences , Bethesda, Maryland.
authors.forename: Allen L
authors.initials: AL
authors.lastname: Richards
mesh_terms: D000818:Animals; D001096:Arachnid Vectors / Q000382:microbiology; D004269:DNA, Bacterial / Q000235:genetics; D003870:Dermacentor / Q000235:genetics / Q000382:microbiology*; D055669:Ecological and Environmental Phenomena; D040362:Geographic Information Systems; D006801:Humans; D008889:Military Personnel; D015995:Prevalence; D060888:Real-Time Polymerase Chain Reaction; D012281:Rickettsia / Q000235:genetics / Q000302:isolation & purification*; D014481:United States
chemical_list: D004269:DNA, Bacterial
keywords: Dermacentor variabilis; Ecological niche modeling; GIS; Rickettsia montanensis; Spotted fever group rickettsiae; Ticks; qPCR