Ehrlichiosis - Species

Species

Five (see note below) species have been shown to cause human infection:

  • Anaplasma phagocytophilum (which causes human granulocytic anaplasmosis, formerly known as human granulocytic ehrlichiosis). A. phagocytophilium is endemic to New England and the north central and Pacific regions of the United States.
  • Ehrlichia ewingii (which causes human ewingii ehrlichiosis). E. ewingii primarily infects deer and dogs (see Ehrlichiosis (canine)). E. ewingii is most common in the south central and southeastern states.
  • Ehrlichia chaffeensis (which causes human monocytic ehrlichiosis). E. chaffeensis is most common in the south central and southeastern states.
  • Ehrlichia canis
  • Neorickettsia sennetsu

The latter two infections are not well studied.

Note: In 2008, human infection by Panola Mountain (Georgia, USA) Ehrlichia species was reported. On August 3, 2011, infection by a yet-unnamed bacterium in the genus Ehrlichia carried by deer ticks that has caused flu-like symptoms in at least 25 people in Minnesota and Wisconsin was reported; human ehrlichiosis was thought to be very rare or absent in Minnesota and Wisconsin. The new species, which is very similar genetically to an Ehrlichia species found in Eastern Europe and Japan called E. muris, was identified at Mayo Clinic Health System's Eau Claire hospital.

Ehrlichia are transported between cells through the host cell filopodia during initial stages of infection, whereas, in the final stages of infection the pathogen ruptures the host cell membrane.

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