New Ehrlichia Species Identified in the United States

The new species closely resembles E. muris, and not the more common ehrlichia species

WEDNESDAY, Aug. 3 (HealthDay News) -- Apart from the usual pathogens Ehrlichia chaffeensis (E. chaffeensis) and E. ewingii implicated as the cause of ehrlichiosis in United States, ehrlichiosis can be caused by a new species that closely resembles E. muris, according to a study published in the Aug. 4 issue of the New England Journal of Medicine.

Bobbi S. Pritt, M.D., from the Mayo Clinic in Rochester, Minn., and colleagues investigated the causes (other than from E. chaffeensis and E. ewingii) of ehrlichiosis in the United States. Molecular methods, culture isolation, and serologic tests were used to diagnose ehrlichiosis.

The investigators identified four cases of ehrlichiosis in Minnesota and Wisconsin that were caused by a newly discovered ehrlichia species, and not by E. chaffeensis or E. ewingii. Fever, malaise, headache, and lymphopenia were observed in all the patients, with thrombocytopenia in three patients and elevated liver enzyme levels in two patients. All the patients recovered with doxycycline treatment. Polymerase chain reaction testing revealed that 17 out of 697 the Ixodes scapularis ticks collected in Minnesota or Wisconsin were positive for the same ehrlichia species. The new ehrlichia species was found to be closely related to E. muris on genetic analyses.

"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," the authors write.

Several authors disclosed financial relationships with pharmaceutical and biomedical companies.

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