Human granulocytic ehrlichiosis as a common cause of tick-associated fever in Southeast Sweden:: Report from a prospective clinical study

Between May and December 1998, tick-associated febrile illness was prospectively studied in Southeast Sweden in order to assess the occurrence of human granulocytic ehrlichiosis (HGE). Inclusion criteria were fever (greater than or equal to 38.0degreesC), with or without headache, myalgia or arthralgia in patients with an observed tick bite or tick exposure within 1 month prior to onset of symptoms. Patients with clinical signs of Lyme borreliosis were included. Of the 27 patients included, we identified 4 cases of HGE. Three of the patients had coinfection with Lyme borreliosis, which presented as erythema migrans. All 27 patients presented with a 2-5 d history of fever. None of the clinical signs or laboratory parameters monitored was helpful in predicting ehrlichiosis in this group with tick-associated fever conditions. Within the HGE-negative group (n = 23), 12 patients had clinical or laboratory signs of Lyme borreliosis. For 11 patients, the actiology of the fever remained unclear. Our results suggest that HGE is common in tick-infested areas of Southeast Sweden, and may occur as a coinfection of Lyme borreliosis. Granulocytic ehrlichiosis should be suspected in patients who present with tick-associated fever, with or without erythema migrans. Ehrlichia serology and PCR should be employed to confirm the diagnosis.