Causes of febrile illnesses after a tick bite in Slovenian children

Background. To establish the etiology in Slovenian children with febrile illnesses occurring after a tick bite. Methods. Eighty-six febrile patients younger than 15 years referred to our institution in 2001 with a history of a tick bite within 6 weeks before onset of the illness were included in this prospective study. Acute and convalescent serum samples were tested for the presence of antibodies to tick-borne encephalitis virus, Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, Ehrlichia chaffeensis, Rickettsia conorii, Babesia microti, Bartonella henselae, Bartonella quintana and Francisella tularensis. Cerebrospinal fluid was investigated in patients in whom meningeal involvement was clinically suspected. Blood and/or cerebrospinal fluid from the patients were cultured in modified Kelly-Pettenkofer medium. PCR was performed to detect ribosomal DNA of A. phagocytophilum and E. chaffeensis. Results. Of 86 patients 33 (38%) were excluded because a well-defined febrile illness not associated with tick bite was established. Tick-borne illness was diagnosed in 28 (53%) of the 53 remaining patients. The most common diagnosis was tick-borne encephalitis (64%), followed by Lyme borreliosis (46%), human monocytic ehrlichiosis and human granulocytic ehrlichiosis (serologic evidence of infection in 9 and 4%, respectively). In 6 (21%) patients there was evidence for infection with more than 1 tick-borne agent. Conclusions. Tick-borne illness was established in 53% of the patients younger than 15 years presenting with febrile illness occurring within 6 weeks after a tick bite. The most common identified illnesses were tick-borne encephalitis and Lyme borreliosis.