Anaplasma phagocytophilum

MICROBIOLOGY

• Cause of tick-borne infection in humans.
• Human granulocytic anaplasmosis (HGA), formerly known as human granulocytic ehrlichiosis (HGE).
  • The organism is currently known as Anaplasma phagocytophilum, transmitted by Ixodes scapularis (black-legged deer tick) on the Eastern Seaboard and in New England, the Mid-Atlantic, and the Upper Midwest, and on the West Coast by the western black-legged tick (Ixodes pacificus)—the same vectors as for Lyme disease (Borrelia burgdorferi).
    • Anaplasma marginale infects cattle.
    • Anaplasma bovis, a cattle pathogen, has caused human disease, first reported in Algeria (1936).
    • Anaplasma capra is provisionally associated with causing moderate to severe disease in humans.
    • Anaplasma bovis-like organism has been described in four patients in the U.S.[3]
      • The four patients hailed from Central and Upper Midwest U.S.
      • Has been identified in Dermacentor variabliis ticks, so it is a possible vector.
  • An obligate, intracellular pathogen that tends to multiply in granulocytes within vacuoles that may form morulae.
    
    • See Ehrlichia spp. module for disease (human monocytic ehrlichiosis [HME] and others) caused by similar tick-borne pathogens.
    • Occasionally seen as a Gram-negative organism upon staining.