Volume 94, Issue 2
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645



Human ehrlichiosis and anaplasmosis are potentially severe illnesses endemic in the United States. Several bacterial agents are known causes of these diseases: , , -like agent, Panola Mountain species, and . Because more than one agent may be present in one area, cases of human ehrlichiosis and anaplasmosis may be reported as “human ehrlichiosis/anaplasmosis undetermined” when the available evidence does not suggest an etiology to the species level. Here, we present a brief summary of these undetermined cases with onset of symptoms from 2008 to 2012 reported to two passive surveillance systems in the United States. The reported incidence rate during this time was 0.52 cases per million person-years. Many cases (24%) had positive polymerase chain reaction results. Enhanced surveillance in an area where several of these etiologic agents are endemic may provide a better understanding of the epidemiology of ehrlichiosis and anaplasmosis in the United States.


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  1. Nichols Heitman K, Dahlgren FS, Drexler N, Massung RF, Barton Behravesh C, , 2016. Increasing incidence of ehrlichiosis in the United States: a summary of national surveillance of Ehrlichia chaffeensis and Ehrlichia ewingii infections in the United States, 2008–2012. Am J Trop Med Hyg 94: 5260. [Google Scholar]
  2. Dahlgren FS, Heitman KN, Drexler NA, Massung RF, Behravesh CB, , 2015. Human granulocytic anaplasmosis in the United States from 2008 to 2012: a summary of national surveillance data. Am J Trop Med Hyg 93: 6672.[Crossref] [Google Scholar]
  3. Centers for Disease Control and Prevention, 2006. Diagnosis and management of tickborne rickettsial diseases: Rocky Mountain spotted fever, ehrlichiosis, and anaplasmosis—United States. MMWR Recomm Rep 55: 127. [Google Scholar]
  4. Anderson BE, Sims KG, Olson JG, Childs JE, Piesman JF, Happ CM, Maupin GO, Johnson BJ, , 1993. Amblyomma americanum: a potential vector of human ehrlichiosis. Am J Trop Med Hyg 49: 239244. [Google Scholar]
  5. Anziani OS, Ewing SA, Barker RW, , 1990. Experimental transmission of a granulocytic form of the tribe Ehrlichieae by Dermacentor variabilis and Amblyomma americanum to dogs. Am J Vet Res 51: 929931. [Google Scholar]
  6. Des Vignes F, Fish D, , 1997. Transmission of the agent of human granulocytic ehrlichiosis by host-seeking Ixodus scapularis (Acari: Ixodidae) in southern New York state. J Med Entomol 34: 379382.[Crossref] [Google Scholar]
  7. Reeves WK, Loftis AD, Nicholson WL, Czarkowski AG, , 2008. The first report of human illness associated with the Panola Mountain Ehrlichia species: a case report. J Med Case Reports 2: 139.[Crossref] [Google Scholar]
  8. Pritt BS, Sloan LM, Johnson DK, Munderloh UG, Paskewitz SM, McElroy KM, McFadden JD, Binnicker MJ, Neitzel DF, Liu G, Nicholson WL, Nelson CM, Franson JJ, Martin SA, Cunningham SA, Steward CR, Bogumill K, Bjorgaard ME, Davis JP, McQuiston JH, Warshauer DM, Wilhelm MP, Patel R, Trivedi VA, Eremeeva ME, , 2011. Emergence of a new pathogenic Ehrlichia species, Wisconsin and Minnesota, 2009. N Engl J Med 365: 422429.[Crossref] [Google Scholar]
  9. Springer YP, Eisen L, Beati L, James AM, Eisen RJ, , 2014. Spatial distribution of counties in the continental United States with records of occurrence of Amblyomma americanum (Ixodida: Ixodidae). J Med Entomol 51: 342351.[Crossref] [Google Scholar]
  10. Hamer SA, Tsao JI, Walker ED, Hickling GJ, , 2010. Invasion of the Lyme disease vector Ixodes scapularis: implications for Borrelia burgdorferi endemicity. EcoHealth 7: 4763.[Crossref] [Google Scholar]
  11. Council of State and Territorial Epidemiologists, 2007. Position Statements 2007 ID-03: Revision of the National Surveillance Case Definition for Ehrlichiosis (Ehrlichiosis/Anaplasmosis). Available at: http://c.ymcdn.com/sites/www.cste.org/resource/resmgr/PS/07-ID-03.pdf. Accessed November 3, 2015. [Google Scholar]
  12. U.S. Census Bureau, Population Division, 2011. Intercensal Estimates of the Resident Population for Counties and States: April 1, 2000 to July 1, 2010. Available at: https://www.census.gov/popest/data/intercensal/county/files/CO-EST00INT-TOT.csv. Accessed November 5, 2015. [Google Scholar]
  13. U.S. Census Bureau, Population Division, 2014. Annual Resident Population Estimates, Estimated Components of Resident Population Change, and Rates of the Components of Resident Population Change for States and Counties: April 1, 2010 to July 1, 2013. Available at: https://www.census.gov/popest/data/counties/totals/2014/files/CO-EST2014-alldata.csv. Accessed November 5, 2015. [Google Scholar]
  14. Gusa AA, Buller RS, Storch GA, Huycke MM, Machado LJ, Slater LN, Stockham SL, Massung RF, , 2001. Identification of a p28 gene in Ehrlichia ewingii: evaluation of gene for use as a target for a species-specific PCR diagnostic assay. J Clin Microbiol 39: 38713876.[Crossref] [Google Scholar]
  15. Dahlgren FS, Mandel EJ, Krebs JW, Massung RF, McQuiston JH, , 2011. Increasing incidence of Ehrlichia chaffeensis and Anaplasma phagocytophilum in the United States, 2000–2007. Am J Trop Med Hyg 85: 124131.[Crossref] [Google Scholar]

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  • Received : 22 Sep 2015
  • Accepted : 19 Oct 2015
  • Published online : 03 Feb 2016

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