II. 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

III. Pathophysiology

  1. Transmission: Tick Borne
    1. Deer Tick Bite (Ixodes Tick)
  2. Small gram-negative organisms
    1. Pleomorphic
    2. Obligate intracellular organisms
    3. Infects Neutrophils
  3. Causative Organism (Rickettsial Disease)
    1. New Name: Anaplasma phagocytophila (Human Granulocytic Anaplasmosis or HGA)
    2. Prior Name: Ehrilichia phagocytophila (Human Granulocytic Ehrlichiosis, renamed in 2001)
    3. Similar organisms affect horses (E. equi) and dogs (E. ewingii)

IV. Risk Factors: Severe Cases

  1. Immunocompromised
  2. Immunosuppressant medications
  3. Organ transplant
  4. Cancer
  5. HIV infection
  6. Splenectomy

V. Symptoms

  1. Occurs 5-14 days after Incubation Period following Tick Bite
    1. Tick Bite recalled in up to 75% of cases
  2. Common Initial Symptoms (flu-like)
    1. Fever
    2. Shaking chills to rigors
    3. Diaphoresis
    4. Myalgias
    5. Severe Headache
    6. Fatigue
  3. Other symptoms
    1. Malaise
    2. Nausea and Vomiting, Anorexia
    3. Abdominal Pain
    4. Diarrhea
    5. Cough
    6. Confusion

VI. Signs: Rash

  1. Occurs in <10% of patients (contrast with >30% in Ehrlichiosis)
  2. Characteristics vary
    1. May be maculopapular or petechial or appear with diffuse erythema
  3. Involves trunk, and spares hands and feet
  4. Not associated with Tick Bite site (unlike Erythema Migrans)

VII. Differential Diagnosis

  1. See Tick Borne Illness
  2. Similar to Ehrlichiosis presentation, and Rocky Mountain Spotted Fever Presentation (with different rash)
  3. Consider coinfection (Lyme Disease, Rocky Mountain Spotted Fever) carried by the same ticks

VIII. 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. Whole Blood Anaplasma PCR (37% Sensitivity)
    1. Most sensitive in first 2 weeks of infection
  4. Anaplasma Serology
    1. Positive two weeks after onset
    2. Used for confirmation, not for diagnosis
    3. Anticipate a fourfold rise in Antibody titers on re-testing at 3-4 weeks
      1. Minimum peak 1:64
      2. Maximum peak 1:128 or higher dilution
  5. Other variably present laboratory findings
    1. Increased Erythrocyte Sedimentation Rate (ESR)
    2. Increased Blood Urea Nitrogen (BUN)
    3. Increased Serum Creatinine

IX. Management

  1. Antibiotic course: 7-14 days
  2. Preferred in all ages (even under age 8 years old)
    1. Doxycycline 2.3 mg/kg up to 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

X. Complications: Untreated Disease

  1. Meningoencephalitis
  2. Respiratory Failure
  3. Uncontrolled Bleeding
  4. Mortality 0.3% (contrast with 3% in Ehrlichiosis)

XI. Prognosis

  1. Severe disease and death are rare, but are more common in Immunocompromised patients

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Related Studies

Ontology: Anaplasma phagocytophilum (bacteria) (C0318329)

Definition (MSH) A species of gram-negative bacteria in the genus ANAPLASMA, family ANAPLASMATACEAE, formerly called Ehrlichia phagocytophila or Ehrlichia equi. This organism is tick-borne (IXODES) and causes disease in horses and sheep. In humans, it causes human granulocytic EHRLICHIOSIS.
Concepts Bacterium (T007)
MSH D041081
SnomedCT 420364006, 422312006, 89725006, 4060003
LNC LP17117-0, MTHU025859
English Ehrlichia equi, Ehrlichia phagocytophila, Rickettsia phagocytophila, Anaplasma phagocytophilum (organism), Anaplasma phagocytophila, Anaplasma phagocytophilum (bacteria), Ehrlichia equi Lewis et al. 1988, Ehrlichia phagocytophila (Foggie 1949) Philip 1962 (Approved Lists 1980), Anaplasma phagocytophilum corrig. (Foggie 1949) Dumler et al. 2001, Cytoecetes bovis, Rickettsia phagocytophila ovis, Anaplasma phagocytophila (organism), Ehrlichia equi (organism), Ehrlichia phagocytophila (organism), Anaplasma phagocytophilum, HGE agent, agent of human granulocytic ehrlichiosis, human granulocytic Ehrlichia, Cytoecetes phagocytophila, HGE Agent
Spanish Anaplasma phagocytophilum (organismo), Ehrlichia equi, Anaplasma phagocytophilum, Anaplasma phagocytophila, Ehrlichia phagocytophila (organismo), Anaplasma phagocytophila (organismo), Ehrlichia equi (organismo), Ehrlichia phagocytophila, Agente de la Ehrlichiosis Granulocítica Humana, Agente de la EGH, Agente de la HGE, Cytoecetes phagocytophila
Swedish Anaplasma phagocytophilum
Czech Anaplasma phagocytophilum, Ehrlichia phagocytophila, Ehrlichia equi
Finnish Anaplasma phagocytophilum
Italian Erlichia equi, Agente dell'HGE, Ehrlichia phagocytophila, Anaplasma phagocytophilum
Polish Anaplasma phagocytophilum
Portuguese Agente da Ehrlichiose Granulocítica Humana, Agente da EGH, Anaplasma phagocytophilum, Ehrlichia equi, Ehrlichia phagocytophila, Agente da HGE, Cytoecetes phagocytophila
French Anaplasma phagocytophilum, Agent EGH, Agent HGE, Agent de l'ehrlichiose granulocytaire humaine, Cytoecetes phagocytophila, Ehrlichia equi, Ehrlichia phagocytophila
German Anaplasma phagocytophilum, Ehrlichia equi, Ehrlichia phagocytophila
Dutch Anaplasma phagocytophilum, Cytoecetes phagocytophilia, Ehrlichia equi, Ehrlichia phagocytophila, HGE-agent

Ontology: Human anaplasmosis due to Anaplasma phagocytophilum (C0483368)

Concepts Disease or Syndrome (T047)
SnomedCT 85708001
English human granulocytic ehrlichiosis (diagnosis), human granulocytic ehrlichiosis, Human granulocytic ehrlichiosis, Human anaplasmosis due to Anaplasma phagocytophilum, Human granulocytic ehrlichiosis (disorder), Infection by Anaplasma phagocytophilum, Human anaplasmosis due to Anaplasma phagocytophilum (disorder)
Spanish anaplasmosis humana debida a Anaplasma phagocytophilum (trastorno), ehrliquiosis granulocítica humana, ehrliquiosis granulocítica humana (trastorno), anaplasmosis humana debida a Anaplasma phagocytophilum, Ehrlichiosis granulocítica humana
Portuguese Ehrliquiose granulocítica humana
Italian Ehrlichiosi granulocitica dell'uomo
German humane Granulozyten-Ehrlichiose
French Erhlichiose granulocytaire humaine
Dutch humane granulocyten-ehrlichiosis
Czech Lidská granulocytická ehrlichióza
Japanese ヒト顆粒球性エールリッヒア症, ヒトカリュウキュウセイエールリッヒアショウ
Hungarian Human granulocytás ehrlichiosis

Ontology: Human anaplasmosis (C1960454)

Concepts Disease or Syndrome (T047)
SnomedCT 427481004
English Human anaplasmosis, Human anaplasmosis (disorder)
Spanish anaplasmosis humana (trastorno), anaplasmosis humana, Anaplasmosis humana
Portuguese Anaplasmose humana
Italian Anaplasmosi umana
German Humane Anaplasmose
French Anaplasmose humaine
Dutch humane anaplasmose
Czech Lidská anaplazmóza
Japanese ヒトアナプラズマショウ, ヒトアナプラズマ症
Hungarian Humán anaplasmosis