EHRLICHIOSIS

The increased incursion of the human population into formerly wild and rural areas during the latter half of this century has precipitated e nhanced awareness of, and concern for, pathogens transmitted by ticks. (63, 71) In addition to established diseases, like Rocky Mountain spot ted fever (RMSF), tularemia, and relapsing fever, tick-borne infection s, such as Lyme disease and babesiosis, have been newly described sinc e 1975. Among these emerging tick-borne diseases are two clinically si milar and geographically diverse illnesses caused by rickettsia of the genus Ehrlichia, recently recognized as agents of human disease in th e United States.