Human Granulocytic Anaplasmosis

Incidence: 1832 reported cases in U.S. in 2014
Majority of cases occur April to September
Tick Carriers
1. Deer Tick (Ixodes Scapularis)
2. Dog tick (Dermacentor variabilis)
United States endemic areas (similar distribution to Lyme Disease)
1. Upper Midwest including. Minnesota
2. Wyoming
3. Northeast including New York

Transmission: Tick Borne
1. Deer Tick Bite (Ixodes Tick)
Small gram-negative organisms
1. Pleomorphic
2. Obligate intracellular organisms
3. Infects Neutrophils
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)

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

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

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

Complete Blood Count
1. Leukopenia
2. Thrombocytopenia (unique to Anaplasmosis compared with Babesia and Lymes Disease)
3. Mild transient Anemia
Liver transaminases increased
1. Aspartate Aminotransferase (AST) increased
2. Alanine Aminotransferase (ALT) increased
Whole Blood Anaplasma PCR (37% Sensitivity)
1. Most sensitive in first 2 weeks of infection
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
Other variably present laboratory findings
1. Increased Erythrocyte Sedimentation Rate (ESR)
2. Increased Blood Urea Nitrogen (BUN)
3. Increased Serum Creatinine

Antibiotic course: 7-14 days
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
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

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