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Human granulocytic anaplasmosis
Classification and external resources
ICD-10 A79.8
ICD-9 083.8
DiseasesDB 31663
MedlinePlus 001381
eMedicine med/3391 ped/655 emerg/159
MeSH D016873

Human granulocytic anaplasmosis (HGA) (previously known as Human granulocytic ehrlichiosis, or HGE[1][2] ) is an infectious disease caused by Anaplasma phagocytophilum, an obligate intracellular bacterium that is typically transmitted to humans by at least three kinds of ticks, including Ixodes scapularis, Ixodes pacificus, and Dermacentor variabilis. These ticks also transmit Lyme disease and other diseases[3].

The bacteria infect white blood cells called neutrophils, causing changes in gene expression that prolong the life of these otherwise short-lived cells.[4]


Ecology & Epidemiology

A. phagocytophilum is transmitted by Ixodes persulcatus group ticks to humans. These ticks are found in the US, Europe, and Asia. In the US, I. scapularis is the tick vector in the East and Midwest states, and I. pacificus in the Pacific Northwest.[5]

The major mammalian reservoir for A. phagocytophilum in the eastern United States is the white-footed mouse, Peromyscus leucopus. Although white-tailed deer harbor Anaplasma phagocytophilum, evidence suggests that they are not a reservoir for the strains that cause HGA. [6]

Anaplasma phagocytophilum shares its tick vector with other human pathogens, and about 10% of patients with HGA show serologic evidence of coinfection with Lyme disease, babesiosis, or tick-borne meningoencephalitis.[7]


Symptoms may include fever, severe headache, muscle aches (myalgia), chills and shaking, similar to the symptoms of influenza. Symptoms may be minor, as evidenced by surveillance studies in high-risk areas. GI symptoms occur in less than half of patients and a skin rash is seen in less than 10% of patients. It is also characterized by thrombocytopenia, leukopenia, and elevated serum transaminase levels in the majority of infected patients.[8]


Clinically, HGA is essentially indistinguishable from Human monocytic ehrlichiosis, the infection caused by Ehrlichia chaffeensis, and other tick-borne illnesses such as Lyme disease may be suspected. As Ehrlichia serologies can be negative in the acute period, PCR is very useful for diagnosis.[9]


If Ehrlichiosis is suspected, treatment should not be delayed while waiting for a definitive laboratory confirmation, as prompt doxycycline therapy has been shown to improve outcomes.[10] Doxycycline is the treatment of choice.

Presentation during early pregnancy can complicate treatment.[11]

Rifampin has been used in pregnancy and in patients allergic to doxycycline.[12]


Although the infectious agent is known to be from the Anaplasma genus, the term "human granulocytic ehrlichiosis" (HGE) is often used, reflecting the prior classification of the organism. E. phagocytophilum and E. equi were reclassified as Anaplasma phagocytophilum.

See also

External links


  1. ^ Malik A, Jameel M, Ali S, Mir S (2005). "Human granulocytic anaplasmosis affecting the myocardium". J Gen Intern Med 20 (10): 958. doi:10.1111/j.1525-1497.2005.00218.x. PMID 16191146.  
  2. ^ Human Anaplasmosis Basics - Minnesota Dept. of Health
  3. ^
  4. ^ PMID: Lee HC, Kioi M, Han J, Puri RK, Goodman JL (September 2008). "Anaplasma phagocytophilum-induced gene expression in both human neutrophils and HL-60 cells". Genomics 92 (3): 144–51. doi:10.1016/j.ygeno.2008.05.005. PMID 18603403.  
  5. ^ Dumler JS, Madigan JE, Pusterla N, Bakken JS (July 2007). "Ehrlichioses in humans: epidemiology, clinical presentation, diagnosis, and treatment". Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 45 Suppl 1: S45–51. doi:10.1086/518146. PMID 17582569.  
  6. ^ Massung RF, Courtney JW, Hiratzka SL, Pitzer VE, Smith G, Dryden RL (October 2005). "Anaplasma phagocytophilum in white-tailed deer". Emerging infectious diseases 11 (10): 1604–6. PMID 16318705.  
  7. ^ Dumler JS, Choi KS, Garcia-Garcia JC, et al. (December 2005). "Human granulocytic anaplasmosis and Anaplasma phagocytophilum". Emerging infectious diseases 11 (12): 1828–34. PMID 16485466.  
  8. ^ Murray, Patrick R.; Rosenthal, Ken S.; Pfaller, Michael A. Medical Microbiology, Fifth Edition. United States: Elsevier Mosby, 2005
  9. ^ Prince LK, Shah AA, Martinez LJ, Moran KA (August 2007). "Ehrlichiosis: making the diagnosis in the acute setting". Southern medical journal 100 (8): 825–8. PMID 17713310.  
  10. ^ Hamburg BJ, Storch GA, Micek ST, Kollef MH (March 2008). "The importance of early treatment with doxycycline in human ehrlichiosis". Medicine 87 (2): 53–60. doi:10.1097/MD.0b013e318168da1d. PMID 18344803.  
  11. ^ Muffly T, McCormick TC, Cook C, Wall J (2008). "Human granulocytic ehrlichiosis complicating early pregnancy". Infect Dis Obstet Gynecol 2008: 359172. doi:10.1155/2008/359172. PMID 18509484. PMC 2396214.  
  12. ^ Krause PJ, Corrow CL, Bakken JS (September 2003). "Successful treatment of human granulocytic ehrlichiosis in children using rifampin". Pediatrics 112 (3 Pt 1): e252–3. PMID 12949322.  


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