Figure 1: Estimated geographic distribution of blacklegged ticks (above) and western blacklegged ticks (below)

Approximate distribution of the Blacklegged tick in the United States of America
Map of the United States showing the approximate distribution of the Western blacklegged tick.  The area affected is the western coast.

Anaplasmosis is a tickborne disease caused by the bacterium Anaplasma phagocytophilum.

  • Tick bites
  • Blood transfusion
    • In rare cases, A. phagocytophilum has been spread by blood transfusion.

Anaplasmosis is most commonly reported in the Northeastern and upper Midwestern states.