Human ehrlichiosis in adults after tick exposure. Diagnosis using polymerase chain reaction

To identify and prospectively follow patients with suspected human ehrlichiosis regarding clinical manifestations, laboratory variables, methods for confirming the diagnosis, and complications.

Prospective case study.

University and Veterans Affairs hospital and clinics.

Observations in 30 adult patients with acute febrile illness or with unexplained fevers and cytopenias or abnormal liver profiles or both.

Serial clinical examinations, hematologic profiles, liver profiles, electrolyte determinations, chest radiographs, and response to therapy; other studies appropriate for patient care.

Therapy with doxycycline.

Thirty cases of ehrlichiosis were identified between 1989 and 1992. Tick exposure was strongly associated with the illness (P = 0.0001). Symptoms were nonspecific; fever, chills, and headache predominated but many other symptoms also occurred. Fever and skin rashes with various morphologic characteristics were the most common physical findings. Laboratory investigations indicate that the hematologic, hepatic, and central nervous systems are commonly involved in human ehrlichiosis. Twenty of 23 patients (87%) tested by the polymerase chain reaction using Ehrlichia chaffeensis sequences and whole blood samples were positive for E. chaffeensis.

The syndrome of human ehrlichiosis is not commonly recognized by physicians. Ehrlichiosis should be considered in the differential diagnosis of patients with febrile illness after known or possible tick exposure, particularly if accompanying cytopenias or abnormal liver profiles or both are present. The therapeutic response to doxycycline is prompt, and complications are uncommon in promptly treated patients. The polymerase chain reaction applied to whole blood samples is a promising test for rapid confirmation of the diagnosis within 24 to 48 hours.