Transmission
Figure 1: Estimated geographic distribution of blacklegged ticks (above) and western blacklegged ticks (below)
Anaplasmosis is a tickborne disease caused by the bacterium Anaplasma phagocytophilum.
- Tick bites
- A. phagocytophilum is primarily spread to people by the bite of an infected tick.
- In the United States, the bacteria is carried by the blacklegged tick (Ixodes scapularis) in the Northeast and Midwestern United States and the western blacklegged tick (Ixodes pacificus) along the West Coast.
- 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.