Lone star tick (Amblyomma americanum) on a persons ankle. These ticks are found mainly in the south-eastern US and are named for the single white mark found on their backs. They are the primary vectors (carriers) of two species of Ehrlichia bacteria, which cause different types of the disease ehrlichiosis. Symptoms of ehrlichiosis range from mild and flu-like to severe and life-threatening, and result from the bacteria infecting and killing white blood cells. Treatment typically involves antibiotics.