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Human Granulocytic Anaplasmosis

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Human Granulocytic Anaplasmosis, HGA, Anaplasma phagocytophila, Human Granulocytic Ehrlichiosis, Ehrlichia equi, Ehrlichia phagocytophila, Human Anaplasmosis, Anaplasmosis

  • Epidemiology
  1. Incidence: 1832 reported cases in U.S. in 2014
  2. Majority of cases occur April to September
  3. Tick Carriers
    1. Deer Tick (Ixodes Scapularis)
    2. Dog tick (Dermacentor variabilis)
  4. United States endemic areas (similar distribution to Lyme Disease)
    1. Upper Midwest including. Minnesota
    2. Wyoming
    3. Northeast including New York
  • Pathophysiology
  1. Transmission: Tick Borne
    1. Deer Tick Bite (Ixodes Tick)
  2. Small gram-negative organisms
    1. Pleomorphic
    2. Obligate intracellular organisms
  3. Disease: Human Granulocytic Anaplasmosis (HGA)
    1. Previously known as: Human Granulocytic Ehrlichiosis
  4. Causative Organism
    1. New Name: Anaplasma phagocytophila
    2. Prior Name: Ehrilichia phagocytophila
    3. Similar organisms affect horses (E. equi) and dogs (E. ewingii)
  • Symptoms (Occur 7-10 days after Tick Bite)
  1. Common Initial Symptoms
    1. Fever
    2. Shaking chills
    3. Myalgias
    4. Severe Headache
  2. Other symptoms
    1. Malaise
    2. Nausea and Vomiting, Anorexia
    3. Abdominal Pain
    4. Diarrhea
    5. Cough
    6. Confusion
  • Signs
  • Rash (occurs in <10% of patients)
  1. Involves trunk
  2. Spares hands and feet
  3. Not associated with Tick Bite site
  • Differential Diagnosis
  1. See Tick Borne Illness
  2. Similar to Ehrlichiosis presentation, and Rocky Mountain Spotted Fever Presentation (with different rash)
  • Labs
  1. Complete Blood Count
    1. Leukopenia
    2. Thrombocytopenia (unique to Anaplasmosis compared with Babesia and Lymes Disease)
    3. Mild transient Anemia
  2. Liver transaminases increased
    1. Aspartate Aminotransferase (AST) increased
    2. Alanine Aminotransferase (ALT) increased
  3. Anaplasma PCR (37% Sensitivity)
  4. Ehrlichiosis Serology
    1. Positive two weeks after onset
    2. Used for confirmation, not for diagnosis
  5. Other variably present laboratory findings
    1. Increased Erythrocyte Sedimentation Rate (ESR)
    2. Increased Blood Urea Nitrogen (BUN)
    3. Increased Serum Creatinine
  • Management
  1. Antibiotic course: 7-14 days
  2. Preferred
    1. Doxycycline 100 mg oral or IV twice daily for 7 to 14 days
  3. Alternatives
    1. Tetracycline 500 mg orally four times daily for 7 to 14 days
    2. Rifampin 10 mg/kg up to 600 mg twice daily for 5 to 7 days
      1. May be used in pregnancy, but increasing resistance