HUMAN EHRLICHIOSIS IN ADULTS AFTER TICK EXPOSURE - DIAGNOSIS USING POLYMERASE CHAIN-REACTION

Objective: To identify and prospectively follow patients with suspecte d human ehrlichiosis regarding clinical manifestations, laboratory var iables, methods for confirming the diagnosis, and complications. Desig n: Prospective case study. Setting: University and Veterans Affairs ho spital and clinics. Patients: Observations in 30 adult patients with a cute febrile illness or with unexplained fevers and cytopenias or abno rmal liver profiles or both. Measurements:Serial clinical examinations , hematologic profiles, liver profiles, electrolyte determinations, ch est radiographs, and response to therapy; other studies appropriate fo r patient care. Intervention: Therapy with doxycycline. Results: Thirt y cases of ehrlichiosis were identified between 1989 and 1992. Tick ex posure was strongly associated with the illness (P = 0.0001). Symptoms were nonspecific; fever, chills, and headache predominated but many o ther symptoms also occurred. Fever and skin rashes with various morpho logic characteristics were the most common physical findings. Laborato ry 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 Ehrli chia chaffeensis sequences and whole blood samples were positive for E . chaffeensis. Conclusions: The syndrome of human ehrlichiosis is not commonly recognized by physicians. Ehrlichiosis should be considered i n the differential diagnosis of patients with febrile illness after kn own or possible tick exposure, particularly if accompanying cytopenias or abnormal liver profiles or both are present. The therapeutic respo nse to doxycycline is prompt, and complications are uncommon in prompt ly treated patients. The polymerase chain reaction applied to whole bl ood samples is a promising test for rapid confirmation of the diagnosi s within 24 to 48 hours.