HUMAN GRANULOCYTIC EHRLICHIOSIS IN THE UPPER MIDWEST UNITED-STATES - A NEW SPECIES EMERGING

Objective.-To characterize the clinical presentation and course, labor atory findings, and treatment outcome of 12 patients with human granul ocytic ehrlichiosis. Setting.-The 12 patients were male, ranged in age from 29 to 91 years, and contracted their illness in Wisconsin or Min nesota. Methods.-Cases were recognized by the presence of intracytopla smic inclusions (morulae) in peripheral neutrophils of patients presen ting with temperature of 38.5 degrees C or higher, chills, severe head ache, and myalgias. All patients had a complete blood cell count and b lood chemistry profile. Blood smears were examined by light microscopy . All available paired serum samples were analyzed for presence of ind irect fluorescent antibodies against Ehrlichia chaffeensis, Ehrlichia phagocytophila, and Ehrlichia equi Blood samples from 12 patients were subjected to polymerase chain reaction analysis using primers specifi c for the E phagocytophilal E equi group, primers that include the age nt identified in our patients, as well as E chaffeensis. Results.-Vary ing combinations of leukopenia, anemia, and thrombocytopenia were foun d in all but one patient. All 12 patients demonstrated morulae in the cytoplasm of neutrophils, but not in mononuclear white blood cells. Se rum assays failed to detect antibodies against E chaffeensis, but eigh t of 10 patients and seven of 10 patients tested had antibody titers o f 1:80 or more for E phagocytophila and E equi, respectively. Polymera se chain reaction products obtained with primers for E phagocytophila, E equi, and the granulocytotropic Ehrlichia revealed that seven patie nts were infected with the same agent. The results of serological assa ys or polymerase chain reaction strongly suggest that all 12 patients were infected by E phagocytophila, E equi, or a closely related Ehrlic hia species. Two of the 12 patients died. The other 10 patients improv ed rapidly with oral doxycycline treatment. Conclusions.-We believe th at all 12 patients have been infected with a granulocytic Ehrlichia sp ecies, reflecting a recently described new disease entity. The infecti ve organism appears to be closely related to E phagocytophila and E eq ui. The geographic domain of human granulocytic ehrlichiosis is curren tly unknown. This novel granulocytic Ehrlichia species is capable of c ausing fatal infections in humans. Early detection and treatment with tetracycline drugs appear to offer the best chance for complete recove ry.