Emergence of a Novel Human Ehrlichia-muris Like Organism in North America – Wisconsin and Minnesota

Bobbi S. Pritt, Mayo Clinic
Lynne M. Sloan, Mayo Clinic
Diep K. Hoang-Johnson, Wisconsin Division of Public Health
Ulrike G. Munderloh, University of Minnesota
Susan M. Paskewitz, University of Wisconsin - Madison
Kristina M. McElroy
Jevon D. McFadden, Wisconsin Division of Public Health
Matthew J. Binnicker, Mayo Clinic
David F. Neitzel, University of Minnesota
Gongping Liu, University of Minnesota
William L. Nicholson, Rickettsial Zoonoses Branch
Curtis M. Nelson, University of Minnesota
Joni J. Franson, Mayo Clinic Health System
Scott A. Martin, Mayo Clinic Health System–Eau Claire
Scott A. Cunningham, Mayo Clinic
Christopher R. Steward, Wisconsin Division of Public Health
Kay Bogumill, Eau Claire City–County Health Department
Mary E. Bjorgaard, Burnett County Department of Health and Human Services
Jeffrey P. Davis, Wisconsin Division of Public Health
Jennifer H. McQuiston, Epidemic Intelligence Service
David M. Warshauer, Wisconsin State Laboratory of Hygiene, Madison
Mark P. Wilhelm, Mayo Clinic
Robin Patel, Mayo Clinic
Vipul A. Trivedi, Mayo Clinic Health System
Marina E. Eremeeva, Georgia Southern University

This is an Accepted Author Manuscript obtained from PMC. The publisher's final edited version of this article is available at The New England Journal of Medicine.


Background: Ehrlichiosis is a clinically important, emerging zoonosis. Only Ehrlichia chaffeensis and E. ewingii have been thought to cause ehrlichiosis in humans in the United States. Patients with suspected ehrlichiosis routinely undergo testing to ensure proper diagnosis and to ascertain the cause.

Methods: We used molecular methods, culturing, and serologic testing to diagnose and ascertain the cause of cases of ehrlichiosis.

Results: On testing, four cases of ehrlichiosis in Minnesota or Wisconsin were found not to be from E. chaffeensis or E. ewingii and instead to be caused by a newly discovered ehrlichia species.

All patients had fever, malaise, headache, and lymphopenia; three had thrombocytopenia; and two had elevated liver-enzyme levels. All recovered after receiving doxycycline treatment. At least 17 of 697 Ixodes scapularis ticks collected in Minnesota or Wisconsin were positive for the same ehrlichia species on polymerase-chain-reaction testing. Genetic analyses revealed that this new ehrlichia species is closely related to E. muris.

Conclusions: We report a new ehrlichia species in Minnesota and Wisconsin and provide supportive clinical, epidemiologic, culture, DNA-sequence, and vector data. Physicians need to be aware of this newly discovered close relative of E. muris to ensure appropriate testing, treatment, and regional surveillance. (Funded by the National Institutes of Health and the Centers for Disease Control and Prevention).