Figure 1: Estimated geographic distribution of lone star ticks (above) and blacklegged ticks (below)
Ehrlichiosis is the general name used to describe diseases caused by the bacteria Ehrlichia chaffeensis, E. ewingii, or E. muris eauclairensis in the United States. The majority of reported cases are due to infection with E. chaffeensis.
- Tick bites
- Most people get ehrlichiosis from the bite of an infected tick.
- In the United States, E. chaffeensis and E. ewingii are carried by the lone star tick (A. americanum) Cdc-pdf[PDF – 2 pages], found primarily in the south-central and eastern United States.
- E. muris eauclairensis is carried by the blacklegged tick (I. scapularis) Cdc-pdf[PDF – 1 page]. While the blacklegged tick is widely distributed in the eastern United States, E. muris eauclairensis has only been found in Wisconsin and Minnesota.
- Blood transfusion and organ transplant
- In rare cases, Ehrlichia species have been spread through blood transfusion and organ transplant.
Ehrlichiosis caused by E. chaffeensis and E. ewingii is most frequently reported from the southeastern and south-central United States, from the East Coast extending westward to Texas.