Epidemiology

History

• 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

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Etiology

Microbiology

• 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]] )

Geography

• 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

Transmission

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

Ticks

• 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
  • Packed Red Blood Cells (see Packed Red Blood Cells, [[Packed Red Blood Cells]])
  • Leukoreduced Red Blood Cells
  • Platelets (see Platelet Transfusion, [[Platelet Transfusion]])
• Nosocomial Transmission (Due to Contact with Blood): case cluster has been reported in China

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Diagnosis

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

Serology

• 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

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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]])

Complications

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]])

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Prevention

• 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

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Treatment

• 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

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Prognosis

• Mortality Rate: <1%

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References

• 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]