Anaplasmosis (Human Granulocytic Anaplasmosis, HGA)



  • Anaplasma Phagocytophilum was First Identified in 1994 as the Agent Causing Anaplasmosis
    • Human Granulocytic Anaplasmosis was Previously Called Human Granulocytic Ehrlichiosis (HGE) (see Ehrlichiosis, [[Ehrlichiosis]]): due to similar clinical manifestations
  • Seasonality: most cases occur in Spring and Summer months
  • Median Age of Patient: 67 y/o
  • Prevalence: appears to be increasing



  • Anaplasma Phagocytophilum (Previously Ehrlichia Phagocytophila and Ehrlichia Equi )
    • Coinfection with Both Anaplasma Phagocytophilum and Borrelia Burgdorferi Have Been Reported in 3-15% of Patients Living in Connecticut and Wisconsin (see Lyme Disease, [[Lyme Disease]] )


  • Anaplasmosis is More Frequently Reported than Ehrlichiosis in the US (see Ehrlichiosis, [[Ehrlichiosis]])
    • Northeast US: Connecticut, Maryland, New York, Rhode Island
    • Upper Midwest US: Minnesota, Wisconsin
    • Western US: along the Pacific coast
    • Europe: mainly Slovenia and Sweden


General Comments

  • Tick Exposure is the Primary Mode of Transmission (see Tick-Borne Illnesses, [[Tick-Borne Illnesses]])
    • Percentage of Cases Associated with Tick Exposure: 45-85% of cases
    • Percentage of Cases Associated with Tick Bite: 67% of cases


  • Ixodes Scapularis (Blacklegged Tick) (see Ixodes Scapularis, [[Ixodes Scapularis]])
    • Ixodes Scapularis is the Same Tick Which is Responsible for Lyme Disease and Babesiosis (see Lyme Disease, [[Lyme Disease]] and Babesiosis, [[Babesiosis]])
  • Ixodes Pacificus (Western Blacklegged Tick): primary tick vector in the western US
  • Ixodes Ricinus: presumed tick vector in Europe

Animal Reservoirs

  • Deer
  • White-Footed Mouse

Incubation Period

  • Incubation Period: 5-21 days

Other Modes of Transmission

  • Blood Transfusion
  • Nosocomial Transmission (Due to Contact with Blood): case cluster has been reported in China


Peripheral Blood Smear (see Peripheral Blood Smear, [[Peripheral Blood Smear]])

  • Findings
    • xxxx

Lumbar Puncture (LP) (see Lumbar Puncture, [[Lumbar Puncture]])

  • Anaplasmosis Cases with Neurologic Findings Usually Have Relatively Normal CSF

Buffy Coat Smear

  • May Be Useful to Detect Intracytoplasmic Inclusions (Morulae)
    • Ehrlichiosis (see Ehrlichiosis, [[Ehrlichiosis]]): inclusions are present in 1-20% of mononuclear cells
    • Anaplasmosis: inclusions are present in 20-80% of neutrophils

PCR for Anaplasma Phagocytophilum DNA

  • xxxx


  • Not Routinely Recommended, Except for Retrospective Diagnosis in Treated Patients
    • Sensitivity of seropositivity <50% on acute-phase serum sample and seropositivity alone does not establish the presence of active infection
  • Indirect Fluorescent Antibody (IFA) is the Preferred and Most Widely-Available Serologic Test for Anaplasmosis: test is available through state health departments

Clinical Manifestations

General Comments

  • Acute Illness (Usually)
    • However, There is a Wide Spectrum of Disease Presentation, Ranging from Subclinical Illness to Subacute Illness to Chronic Illness: cases with fever lasting as long as 51 days have been reported
    • In Studies of Patients with Transfusion-Related Disease, Donors were Asymptomatic (Transfusion, 2013) [MEDLINE]
  • Severity of Illness
    • More Severe Disease Occurs in Patients with Immunocompromised States (HIV, etc) or Other Co-Morbid Disease
  • Incubation Period: 5-21 days

Initial Clinical Features

  • Fever (see Fever, [[Fever]])
  • Headache (see Headache, [[Headache]])
  • Leukopenia (see Leukopenia, [[Leukopenia]])
  • Malaise
  • Myalgias (see Myalgias, [[Myalgias]])
  • Rash: rarely occurs
    • If Rash is Present in Presumed Anaplasmosis, This Should raise the Suspicion of Possible Co-Infection with Borrelia Burgdorferi or an Alternative Diagnosis Such as Rocky Mountain Spotted Fever or Meningococcemia)
  • Thrombocytopenia (see Thrombocytopenia, [[Thrombocytopenia]])
  • Transaminitis (see Elevated Liver Function Tests, [[Elevated Liver Function Tests]])
  • Vomiting (see Nausea and Vomiting, [[Nausea and Vomiting]])


Infectious Complications

  • General Comments: may be serious or fatal
  • Candidiasis (see Candida, [[Candida]])
  • Herpes Simplex Virus (HSV) Esophagitis (see Herpes Simplex Virus, [[Herpes Simplex Virus]])
  • Invasive Aspergillosis (see xxxx, [[xxxx]])
  • Sepsis/Toxic Shock-Like Syndrome (see Hypotension, [[Hypotension]])

Neurologic Manifestations

  • Brachial Plexopathy
  • Demyelinating Polyneuropathy (see Peripheral Neuropathy, [[Peripheral Neuropathy]])


  • Prompt Removal of Ticks: it takes approximately 24-48 hrs of tick attachment to transmit Anaplasma Phagocytophilum in animal studies
  • Tick Repellants
    • DEET (N,N-diethyl-3-methylbenzamide): previously called N,N-diethyl-m-toluamide
    • Permethrin


  • Chloramphenicol (see Chloramphenicol, [[Chloramphenicol]]): equally effective as tetracyline
    • Regimen: 7-10 days
  • Tetracyclines (see Tetracyclines, [[Tetracyclines]]): equally effective as chloramphenicol
    • Doxycycline (see Doxycycline, [[Doxycycline]]): failure to defervesce within 48 h of initiation of doxycycline is evidence against the diagnosis of anaplasmosis
      • Regimen: 7-10 days


  • Mortality Rate: <1%


  • Anaplasma and Ehrlichia infection. Ann N Y Acad Sci. 2005;1063:361 [MEDLINE]
  • Nosocomial transmission of human granulocytic anaplasmosis in China. JAMA. 2008;300(19):2263 [MEDLINE]
  • Transfusion-transmitted anaplasmosis from leukoreduced red blood cells. Transfusion. 2013 Jan;53(1):181-6. Epub 2012 May 7 [MEDLINE]
  • CDC Tickborne Diseases of the United States (Accessed 7/17) [LINK]