Ehrlichia muris eauclarensis in ticks

Several species of Ehrlichia bacteria can be carried by ticks, and species like E. chaffeensis and E. ewingii are some of the most common pathogens found in North American Amblyomma ticks like the Lone star tick (Amblyomma americanum). A less-common species in this genus is named Ehrlichia muris eauclairenis (EME), and is one of the several pathogens we find in deer ticks (Ixodes scapularis). This pathogen is most often found in parts of the Midwestern U.S., especially Minnesota and Wisconsin.

Ehrlichia muris eauclairensis in Massachusetts

While EME tends to be focused in Upper Midwest, it can pop up from time to time in other spots with large deer tick populations; a 2023 publication based in part on TickReport passive surveillance data found four separate ticks infected with this pathogen in ticks submitted from the state of Massachusetts, which was supported by additional data gathered from ticks and rodents collected in the state through other projects.

This adult female Ixodes scapularis tick tested positive for EME in October 2023.

Ehrlichiosis caused by Ehrlichia muris

While health care providers (and tick researchers!) don’t see illness caused by this pathogen very often (ten or fewer cases have been reported per year since 2009), this species of Ehrlichia fortunately does not seem to cause severe illness as frequently as other species like E. chaffeensis. Common symptoms include flu-like symptoms of fever, headache, fatigue, muscle pain, as well as gastrointestinal complaints. More information on symptoms can be found on the CDC’s Ehrlichiosis page.